v0.5.4

This reverts commit 7332c6a.
Non-static userdata is a special case and can cause segfault if try to serialize it.
Now it should be safe, plus I added non-static userdata destructor to generate better error messages
in case of accessing destructed userdata.

.github/workflows/coverage.yml

@@ -0,0 +1,23 @@
+name: coverage
+on: [push]
+
+jobs:
+  test:
+    name: coverage
+    runs-on: ubuntu-latest
+    container:
+      image: xd009642/tarpaulin
+      options: --security-opt seccomp=unconfined
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Generate code coverage
+        run: |
+          cargo tarpaulin --verbose --features lua53,vendored,async,send,serialize --out xml --exclude-files benches --exclude-files tests --exclude-files build --exclude-files src/ffi
+
+      - name: Upload to codecov.io
+        uses: codecov/codecov-action@v1
+        with:
+          token: ${{secrets.CODECOV_TOKEN}}
+          fail_ci_if_error: false

.github/workflows/main.yml

@@ -7,150 +7,207 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        thing:
-        - stable
-        - macos-x86_64
-        - x86_64-msvc
+        os: [ubuntu-18.04, macos-latest, windows-latest]
+        rust: [stable]
+        lua: [lua54, lua53, lua52, lua51, luajit]
         include:
-        - thing: stable
+        - os: ubuntu-18.04
           target: x86_64-unknown-linux-gnu
-          rust: stable
-          os: ubuntu-latest
-        - thing: macos-x86_64
+        - os: macos-latest
           target: x86_64-apple-darwin
-          rust: stable
-          os: macos-latest
-        - thing: x86_64-msvc
+        - os: windows-latest
           target: x86_64-pc-windows-msvc
-          rust: stable-x86_64-msvc
-          os: windows-latest
     steps:
-    - uses: actions/checkout@v1
-    - name: Install Rust (rustup)
-      if: matrix.os != 'macos-latest'
-      run: rustup update ${{ matrix.rust }} --no-self-update && rustup default ${{ matrix.rust }}
-      shell: bash
-    - name: Install Lua (ubuntu)
-      if: matrix.os == 'ubuntu-latest'
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: ${{ matrix.rust }}
+        target: ${{ matrix.target }}
+        override: true
+    - name: Build ${{ matrix.lua }} vendored
       run: |
-        sudo apt-get update -y
+        cargo build --release --features "${{ matrix.lua }} vendored"
+        cargo build --release --features "${{ matrix.lua }} vendored async send serialize"
+      shell: bash
+    - name: Build ${{ matrix.lua }} pkg-config
+      if: ${{ matrix.os == 'ubuntu-18.04' && matrix.lua != 'lua54' }}
+      run: |
+        sudo apt-get update
         sudo apt-get install -y --no-install-recommends liblua5.3-dev liblua5.2-dev liblua5.1-0-dev libluajit-5.1-dev
-    - name: Install Rust (macos)
-      if: matrix.os == 'macos-latest'
+        cargo build --release --features "${{ matrix.lua }}"
+
+  build_aarch64_cross_macos:
+    name: Cross-compile to aarch64-apple-darwin
+    runs-on: macos-11.0
+    needs: build
+    strategy:
+      matrix:
+        lua: [lua54, lua53, lua52, lua51, luajit]
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        target: aarch64-apple-darwin
+        override: true
+    - name: Cross-compile
+      run: cargo build --target aarch64-apple-darwin --features "${{ matrix.lua }} async send serialize vendored"
+
+  build_aarch64_cross_ubuntu:
+    name: Cross-compile to aarch64-unknown-linux-gnu
+    runs-on: ubuntu-18.04
+    needs: build
+    strategy:
+      matrix:
+        lua: [lua54, lua53, lua52, lua51, luajit]
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        target: aarch64-unknown-linux-gnu
+        override: true
+    - name: Install ARM compiler toolchain
       run: |
-        curl https://sh.rustup.rs | sh -s -- -y
-        echo ::add-path::$HOME/.cargo/bin
-      shell: bash
-    - name: Install GCC (aarch64-linux)
-      run: |
-        sudo apt-get update -y
+        sudo apt-get update
         sudo apt-get install -y --no-install-recommends gcc-aarch64-linux-gnu libc6-dev-arm64-cross
-      if: matrix.thing == 'aarch64-linux'
       shell: bash
-    - run: rustup target add ${{ matrix.target }}
-    - name: Build (Lua 5.3/5.2/5.1 and LuaJIT vendored+async)
-      run: |
-        for FEATURE in lua53 lua52 lua51 luajit; do
-          echo "Building $FEATURE"
-          cargo build --target ${{ matrix.target }} --release --no-default-features --features "$FEATURE vendored async"
-        done
-      shell: bash
-    - name: Build (Lua 5.3/5.2/5.1 and LuaJIT via pkg-config)
-      if: matrix.os == 'ubuntu-latest'
-      run: |
-        for FEATURE in lua53 lua52 lua51 luajit; do
-          echo "Building $FEATURE"
-          cargo build --target ${{ matrix.target }} --release --no-default-features --features $FEATURE
-        done
+    - name: Cross-compile
+      run: cargo build --target aarch64-unknown-linux-gnu --features "${{ matrix.lua }} async send serialize vendored"
       shell: bash
 
-  test_linux:
-    name: Test on Linux
-    runs-on: ubuntu-latest
+  build_armv7_cross_ubuntu:
+    name: Cross-compile to armv7-unknown-linux-gnueabihf
+    runs-on: ubuntu-18.04
     needs: build
+    strategy:
+      matrix:
+        lua: [lua54, lua53, lua52, lua51]
     steps:
-    - uses: actions/checkout@v1
-    - name: Install Rust
-      run: rustup update stable --no-self-update && rustup default stable
-      shell: bash
-    - name: Run tests (Lua 5.3 vendored)
-      run: cargo test --release --no-default-features --features "lua53 vendored"
-      shell: bash
-    - name: Run tests (Lua 5.3 vendored+async)
-      run: cargo test --release --no-default-features --features "lua53 vendored async"
-      shell: bash
-    - name: Run tests (Lua 5.2 vendored)
-      run: cargo test --release --no-default-features --features "lua52 vendored"
-      shell: bash
-    - name: Run tests (Lua 5.1 vendored)
-      run: cargo test --release --no-default-features --features "lua51 vendored"
-      shell: bash
-    - name: Run tests (Lua 5.1 vendored+async)
-      run: cargo test --release --no-default-features --features "lua51 vendored async"
-      shell: bash
-    - name: Run tests (LuaJIT vendored)
-      run: cargo test --release --no-default-features --features "luajit vendored"
-      shell: bash
-    - name: Run tests (LuaJIT vendored+async)
-      run: cargo test --release --no-default-features --features "luajit vendored async"
-      shell: bash
-    - name: Run compile test (Lua 5.3)
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        target: armv7-unknown-linux-gnueabihf
+        override: true
+    - name: Install ARM compiler toolchain
       run: |
-        sudo apt-get update -y
-        sudo apt-get install -y --no-install-recommends liblua5.3-dev
-        cargo test --release --no-default-features --features "lua53 vendored" -- --ignored
+        sudo apt-get update
+        sudo apt-get install -y --no-install-recommends gcc-arm-linux-gnueabihf libc-dev-armhf-cross
+      shell: bash
+    - name: Cross-compile
+      run: cargo build --target armv7-unknown-linux-gnueabihf --features "${{ matrix.lua }} async send serialize vendored"
+      shell: bash
 
-  test_macos:
-    name: Test on MacOS
-    runs-on: macos-latest
+  test:
+    name: Test
+    runs-on: ${{ matrix.os }}
     needs: build
+    strategy:
+      matrix:
+        os: [ubuntu-18.04, macos-latest, windows-latest]
+        rust: [stable]
+        lua: [lua54, lua53, lua52, lua51, luajit]
+        include:
+        - os: ubuntu-18.04
+          target: x86_64-unknown-linux-gnu
+        - os: macos-latest
+          target: x86_64-apple-darwin
+        - os: windows-latest
+          target: x86_64-pc-windows-msvc
     steps:
-    - uses: actions/checkout@v1
-    - name: Install Rust
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: ${{ matrix.rust }}
+        target: ${{ matrix.target }}
+        override: true
+    - name: Run ${{ matrix.lua }} tests
       run: |
-        curl https://sh.rustup.rs | sh -s -- -y
-        echo ::add-path::$HOME/.cargo/bin
+        cargo test --release --features "${{ matrix.lua }} vendored"
+        cargo test --release --features "${{ matrix.lua }} vendored async send serialize"
       shell: bash
-    - name: Run tests (Lua 5.3 vendored)
-      run: cargo test --release --no-default-features --features "lua53 vendored"
-      shell: bash
-    - name: Run tests (Lua 5.2 vendored)
-      run: cargo test --release --no-default-features --features "lua52 vendored"
-      shell: bash
-    - name: Run tests (Lua 5.1 vendored)
-      run: cargo test --release --no-default-features --features "lua51 vendored"
-      shell: bash
-    - name: Run tests (LuaJIT vendored)
-      run: cargo test --release --no-default-features --features "luajit vendored"
+    - name: Run compile tests (macos lua53)
+      if: ${{ matrix.os == 'macos-latest' && matrix.lua == 'lua53' }}
+      run: |
+        TRYBUILD=overwrite cargo test --release --features "${{ matrix.lua }} vendored" -- --ignored
+        TRYBUILD=overwrite cargo test --release --features "${{ matrix.lua }} vendored async send serialize" -- --ignored
       shell: bash
 
-  test_windows:
-    name: Test on Windows
+  test_modules:
+    name: Test modules
+    runs-on: ${{ matrix.os }}
+    needs: build
+    strategy:
+      matrix:
+        os: [ubuntu-18.04, macos-latest]
+        rust: [stable]
+        lua: [lua54, lua53, lua52, lua51, luajit]
+        include:
+        - os: ubuntu-18.04
+          target: x86_64-unknown-linux-gnu
+        - os: macos-latest
+          target: x86_64-apple-darwin
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: ${{ matrix.rust }}
+        target: ${{ matrix.target }}
+        override: true
+    - name: Run ${{ matrix.lua }} module tests
+      run: |
+        (cd examples/module && cargo build --release --features "${{ matrix.lua }} vendored")
+        (cd tests/module && cargo test --release --features "${{ matrix.lua }} vendored")
+      shell: bash
+
+  test_modules_windows:
+    name: Test modules on Windows
     runs-on: windows-latest
     needs: build
+    strategy:
+      matrix:
+        lua: [lua53, luajit]
+    defaults:
+      run:
+        shell: msys2 {0}
     steps:
-    - uses: actions/checkout@v1
-    - name: Install Rust
-      run: rustup update stable --no-self-update && rustup default stable
-      shell: bash
-    - name: Run tests (Lua 5.3 vendored)
-      run: cargo test --release --no-default-features --features "lua53 vendored"
-      shell: bash
-    - name: Run tests (Lua 5.2 vendored)
-      run: cargo test --release --no-default-features --features "lua52 vendored"
-      shell: bash
-    - name: Run tests (Lua 5.1 vendored)
-      run: cargo test --release --no-default-features --features "lua51 vendored"
-      shell: bash
-    - name: Run tests (LuaJIT vendored)
-      run: cargo test --release --no-default-features --features "luajit vendored"
-      shell: bash
+    - uses: msys2/setup-msys2@v2
+    - uses: actions/checkout@v2
+    - name: Install Rust & Lua
+      run: |
+        pacman -S --noconfirm mingw-w64-x86_64-rust mingw-w64-x86_64-lua mingw-w64-x86_64-luajit mingw-w64-x86_64-pkg-config
+    - name: Run ${{ matrix.lua }} module tests
+      run: |
+        (cd examples/module && cargo build --release --features "${{ matrix.lua }}")
+        (cd tests/module && cargo test --release --features "${{ matrix.lua }}")
 
   rustfmt:
     name: Rustfmt
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     steps:
-    - uses: actions/checkout@v1
-    - name: Install Rust
-      run: rustup update stable && rustup default stable && rustup component add rustfmt
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        components: rustfmt
+        override: true
     - run: cargo fmt -- --check
+
+  clippy:
+    name: Clippy check
+    runs-on: ubuntu-18.04
+    strategy:
+      matrix:
+        lua: [lua54, lua53, lua52, lua51, luajit]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+            toolchain: nightly
+            components: clippy
+            override: true
+      - uses: actions-rs/clippy-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --features "${{ matrix.lua }},vendored,async,send,serialize

CHANGELOG.md

@@ -0,0 +1,52 @@
+## v0.5.4
+
+- Build script improvements
+- Improvements in panic handling (resume panic on value popping)
+- Fixed bug serializing 3rd party userdata (causes segfault)
+- Make error::Error non exhaustive
+
+## v0.5.3
+
+- Fixed bug when returning nil-prefixed multi values from async function (+ test)
+- Performance optimisation for async callbacks (polling)
+
+## v0.5.2
+
+- Some performance optimisations (callbacks)
+- `ToLua` implementation for `Cow<str>` and `Cow<CStr>`
+- Fixed bug with `Scope` destruction of partially polled futures
+
+## v0.5.1
+
+- Support cross compilation that should work well for vendored builds (including LuaJIT with some restrictions)
+- Fix numeric types conversion for 32bit Lua
+- Update tokio to 1.0 for async examples
+
+## v0.5.0
+
+- Serde support under `serialize` feature flag.
+- Re-export `mlua_derive`.
+- impl `ToLua` and `FromLua` for `HashSet` and `BTreeSet`
+
+## v0.4.2
+
+- Added `Function::dump()` to dump lua function to a binary chunk
+- Added `ChunkMode` enum to mark chunks as text or binary
+- Updated `set_memory_limit` doc
+
+## v0.4.0
+
+- Lua 5.4 support with `MetaMethod::Close`.
+- `lua53` feature is disabled by default. Now preferred Lua version have to be chosen explicitly.
+- Provide safety guaraness for Lua state, which means that potenially unsafe operations, like loading C modules (using `require` or `package.loadlib`) are disabled. Equalient for the previous `Lua::new()` function is `Lua::unsafe_new()`.
+- New `send` feature to require `Send`.
+- New `module` feature, that disables linking to Lua Core Libraries. Required for modules.
+- Don't allow `'callback` outlive `'lua` in `Lua::create_function()` to fix [the unsoundness](tests/compile/static_callback_args.rs).
+- Added `Lua::into_static()` to make `'static` Lua state. This is useful to spawn async Lua threads that requires `'static`.
+- New function `Lua::set_memory_limit()` (similar to `rlua`) to enable memory restrictions in Lua VM (requires Lua >= 5.2).
+- `Scope`, temporary removed in v0.3, is back with async support.
+- Removed deprecated `Table::call()` function.
+- Added hooks support (backported from rlua 0.17).
+- New `AnyUserData::has_metamethod()` function.
+- LuaJIT 2.0.5 (the latest stable) support.
+- Various bug fixes and improvements.

Cargo.toml

@@ -1,71 +1,93 @@
 [package]
 name = "mlua"
-version = "0.3.1"
+version = "0.5.4" # remember to update html_root_url and mlua_derive
 authors = ["Aleksandr Orlenko <zxteam@pm.me>", "kyren <catherine@chucklefish.org>"]
 edition = "2018"
 repository = "https://github.com/khvzak/mlua"
 documentation = "https://docs.rs/mlua"
 readme = "README.md"
-keywords = ["lua", "luajit", "async", "futures"]
+keywords = ["lua", "luajit", "async", "futures", "scripting"]
 categories = ["api-bindings", "asynchronous"]
 license = "MIT"
 links = "lua"
 build = "build/main.rs"
 description = """
-High level bindings to Lua 5.1/5.2/5.3 (including LuaJIT)
+High level bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT)
 with async/await features and support of writing native lua modules in Rust.
 """
 
-[badges]
-# github-actions = { repository = "khvzak/mlua", workflow = "CI" }
-
 [package.metadata.docs.rs]
-features = ["async"]
+features = ["lua53", "async", "send", "serialize"]
+rustdoc-args = ["--cfg", "docsrs"]
 
 [workspace]
 members = [
     "mlua_derive",
+    "examples/module",
+    "tests/module",
 ]
 
 [features]
-default = ["lua53"]
+lua54 = []
 lua53 = []
 lua52 = []
 lua51 = []
 luajit = []
 vendored = ["lua-src", "luajit-src"]
+module = ["mlua_derive"]
 async = ["futures-core", "futures-task", "futures-util"]
+send = []
+serialize = ["serde", "erased-serde"]
 
 [dependencies]
+mlua_derive = { version = "0.5", optional = true, path = "mlua_derive" }
 bstr = { version = "0.2", features = ["std"], default_features = false }
-num-traits = { version = "0.2.11" }
-futures-core = { version = "0.3.4", optional = true }
-futures-task = { version = "0.3.4", optional = true }
-futures-util = { version = "0.3.4", optional = true }
+lazy_static = { version = "1.4" }
+num-traits = { version = "0.2.14" }
+futures-core = { version = "0.3.5", optional = true }
+futures-task = { version = "0.3.5", optional = true }
+futures-util = { version = "0.3.5", optional = true }
+serde = { version = "1.0", optional = true }
+erased-serde = { version = "0.3", optional = true }
 
 [build-dependencies]
 cc = { version = "1.0" }
 pkg-config = { version = "0.3.17" }
-lua-src = { version = "535.0.1", optional = true }
-luajit-src = { version = "210.0.0", optional = true }
+lua-src = { version = ">= 540.0.0, < 550.0.0", optional = true }
+luajit-src = { version = ">= 210.1.2, < 220.0.0", optional = true }
 
 [dev-dependencies]
-rustyline = "6.0"
-criterion = "0.3"
+rustyline = "7.0"
+criterion = { version = "0.3.4", features = ["html_reports", "async_tokio"] }
 trybuild = "1.0"
-futures = "0.3.4"
-hyper = "0.13"
-tokio = { version = "0.2.18", features = ["full"] }
+futures = "0.3.5"
+hyper = { version = "0.14", features = ["client", "server"] }
+reqwest = { version = "0.11", features = ["json"] }
+tokio = { version = "1.0", features = ["full"] }
 futures-timer = "3.0"
+serde_json = "1.0"
 
 [[bench]]
 name = "benchmark"
 harness = false
+required-features = ["async"]
+
+[[example]]
+name = "async_http_client"
+required-features = ["async"]
+
+[[example]]
+name = "async_http_reqwest"
+required-features = ["async", "serialize"]
+
+[[example]]
+name = "async_http_server"
+required-features = ["async", "send"]
 
 [[example]]
 name = "async_tcp_server"
 required-features = ["async"]
 
 [[example]]
-name = "async_http_client"
-required-features = ["async"]
+name = "serialize"
+required-features = ["serialize"]

LICENSE

@@ -3,7 +3,7 @@ below:
 
 MIT License
 
-Copyright (c) 2019 A. Orlenko
+Copyright (c) 2019-2021 A. Orlenko
 Copyright (c) 2017 rlua
 
 Permission is hereby granted, free of charge, to any person obtaining a copy

README.md

@@ -1,5 +1,5 @@
 # mlua
-[![Build Status]][github-actions] [![Latest Version]][crates.io] [![API Documentation]][docs.rs]
+[![Build Status]][github-actions] [![Latest Version]][crates.io] [![API Documentation]][docs.rs] [![Coverage Status]][codecov.io]
 
 [Build Status]: https://github.com/khvzak/mlua/workflows/CI/badge.svg
 [github-actions]: https://github.com/khvzak/mlua/actions
@@ -7,30 +7,75 @@
 [crates.io]: https://crates.io/crates/mlua
 [API Documentation]: https://docs.rs/mlua/badge.svg
 [docs.rs]: https://docs.rs/mlua
+[Coverage Status]: https://codecov.io/gh/khvzak/mlua/branch/master/graph/badge.svg?token=99339FS1CG
+[codecov.io]: https://codecov.io/gh/khvzak/mlua
 
 [Guided Tour](examples/guided_tour.rs)
 
-A fork of [rlua 0.15](https://github.com/kyren/rlua/tree/0.15.3) which provides a high level
-interface between Rust and Lua. Unlike `rlua` , `mlua` supports Lua 5.1 (including LuaJIT), 5.2 and 5.3.
-The `mlua` goal is to be an easy to use, practical and flexible API between Rust and Lua but
-*__not__* always 100% safe due to the Lua VM nature. Also, `mlua` provides a way to write native lua
-modules in Rust.
+`mlua` is bindings to [Lua](https://www.lua.org) programming language for Rust with a goal to provide
+_safe_ (as far as it's possible), high level, easy to use, practical and flexible API.
+
+Started as [rlua](https://github.com/amethyst/rlua/tree/0.15.3) fork, `mlua` supports Lua 5.4, 5.3, 5.2 and 5.1 including LuaJIT (2.0.5 and 2.1 beta) and allows to write native Lua modules in Rust as well as use Lua in a standalone mode.
+
+`mlua` tested on Windows/macOS/Linux including module mode in [GitHub Actions] on `x86_64` platform and cross-compilation to `aarch64` (other targes are also supported).
+
+[GitHub Actions]: https://github.com/khvzak/mlua/actions
 
 ## Usage
 
+### Feature flags
+
+`mlua` uses feature flags to reduce the amount of depenendies, compiled code and allow to choose only required set of features.
+Below is a list of the available feature flags. By default `mlua` does not enable any features.
+
+* `lua54`: activate Lua [5.4] support
+* `lua53`: activate Lua [5.3] support
+* `lua52`: activate Lua [5.2] support
+* `lua51`: activate Lua [5.1] support
+* `luajit`: activate [LuaJIT] support
+* `vendored`: build static Lua(JIT) library from sources during `mlua` compilation using [lua-src] or [luajit-src] crates
+* `module`: enable module mode (building loadable `cdylib` library for Lua)
+* `async`: enable async/await support (any executor can be used, eg. [tokio] or [async-std])
+* `send`: make `mlua::Lua` transferable across thread boundaries (adds [`Send`] requirement to `mlua::Function` and `mlua::UserData`)
+* `serialize`: add serialization and deserialization support to `mlua` types usign [serde] framework
+
+[5.4]: https://www.lua.org/manual/5.4/manual.html
+[5.3]: https://www.lua.org/manual/5.3/manual.html
+[5.2]: https://www.lua.org/manual/5.2/manual.html
+[5.1]: https://www.lua.org/manual/5.1/manual.html
+[LuaJIT]: https://luajit.org/
+[lua-src]: https://github.com/khvzak/lua-src-rs
+[luajit-src]: https://github.com/khvzak/luajit-src-rs
+[tokio]: https://github.com/tokio-rs/tokio
+[async-std]: https://github.com/async-rs/async-std
+[`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
+[serde]: https://github.com/serde-rs/serde
+
 ### Async/await support
 
-Starting from 0.3, mlua supports async/await for all Lua versions. This works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6) and require running [Thread](https://docs.rs/mlua/latest/mlua/struct.Thread.html) along with enabling `async` feature in `Cargo.toml`.
+`mlua` supports async/await for all Lua versions. This works using Lua [coroutines](https://www.lua.org/manual/5.3/manual.html#2.6) and require running [Thread](https://docs.rs/mlua/latest/mlua/struct.Thread.html) along with enabling `feature = "async"` in `Cargo.toml`.
 
 **Examples**:
 - [HTTP Client](examples/async_http_client.rs)
+- [HTTP Client (json)](examples/async_http_reqwest.rs)
+- [HTTP Server](examples/async_http_server.rs)
 - [TCP Server](examples/async_tcp_server.rs)
 
-### Choosing Lua version
+### Serialization (serde) support
 
-The following features could be used to choose Lua version: `lua53` (default), `lua52`, `lua51` and `luajit`.
+With `serialize` feature flag enabled, `mlua` allows you to serialize/deserialize any type that implements [`serde::Serialize`] and [`serde::Deserialize`] into/from [`mlua::Value`]. In addition `mlua` provides [`serde::Serialize`] trait implementation for it (including `UserData` support).
 
-By default mlua uses `pkg-config` tool to find lua includes and lib.
+[Example](examples/serialize.rs)
+
+[`serde::Serialize`]: https://docs.serde.rs/serde/ser/trait.Serialize.html
+[`serde::Deserialize`]: https://docs.serde.rs/serde/de/trait.Deserialize.html
+[`mlua::Value`]: https://docs.rs/mlua/latest/mlua/enum.Value.html
+
+### Compiling
+
+You have to enable one of the features `lua54`, `lua53`, `lua52`, `lua51` or `luajit`, according to the choosen Lua version.
+
+By default `mlua` uses `pkg-config` tool to find lua includes and libraries for the chosen Lua version.
 In most cases it works as desired, although sometimes could be more preferable to use a custom lua library.
 To achieve this, mlua supports `LUA_INC`, `LUA_LIB`, `LUA_LIB_NAME` and `LUA_LINK` environment variables.
 `LUA_LINK` is optional and may be `dylib` (a dynamic library) or `static` (a static library, `.a` archive).
@@ -42,14 +87,16 @@ my_project $ LUA_INC=$HOME/tmp/lua-5.2.4/src LUA_LIB=$HOME/tmp/lua-5.2.4/src LUA
 
 `mlua` also supports vendored lua/luajit using the auxilary crates [lua-src](https://crates.io/crates/lua-src) and
 [luajit-src](https://crates.io/crates/luajit-src).
-Just enable the `vendored` feature and cargo will automatically build and link specified lua/luajit version. This is the easiest way to get started with mlua.
+Just enable the `vendored` feature and cargo will automatically build and link specified lua/luajit version. This is the easiest way to get started with `mlua`.
 
 ### Standalone mode
+In a standalone mode `mlua` allows to add to your application scripting support with a gently configured Lua runtime to ensure  safety and soundness.
+
 Add to `Cargo.toml` :
 
 ``` toml
 [dependencies]
-mlua = "0.3"
+mlua = { version = "0.5", features = ["lua53", "vendored"] }
 ```
 
 `main.rs`
@@ -73,6 +120,9 @@ fn main() -> LuaResult<()> {
 ```
 
 ### Module mode
+In a module mode `mlua` allows to create a compiled Lua module that can be loaded from Lua code using [`require`](https://www.lua.org/manual/5.3/manual.html#pdf-require). In this case `mlua` uses an external Lua runtime which could lead to potential unsafety due to unpredictability of the Lua environment and usage of libraries such as [`debug`](https://www.lua.org/manual/5.3/manual.html#6.10).
+
+[Example](examples/module)
 
 Add to `Cargo.toml` :
 
@@ -81,15 +131,12 @@ Add to `Cargo.toml` :
 crate-type = ["cdylib"]
 
 [dependencies]
-mlua = "0.3"
-mlua_derive = "0.3"
+mlua = { version = "0.5", features = ["lua53", "vendored", "module"] }
 ```
 
 `lib.rs` :
 
 ``` rust
-#[macro_use]
-extern crate mlua_derive;
 use mlua::prelude::*;
 
 fn hello(_: &Lua, name: String) -> LuaResult<()> {
@@ -97,7 +144,7 @@ fn hello(_: &Lua, name: String) -> LuaResult<()> {
     Ok(())
 }
 
-#[lua_module]
+#[mlua::lua_module]
 fn my_module(lua: &Lua) -> LuaResult<LuaTable> {
     let exports = lua.create_table()?;
     exports.set("hello", lua.create_function(hello)?)?;
@@ -105,27 +152,48 @@ fn my_module(lua: &Lua) -> LuaResult<LuaTable> {
 }
 ```
 
-And then (macos example):
+And then (**macOS** example):
 
 ``` sh
-$ cargo build
+$ cargo rustc -- -C link-arg=-undefined -C link-arg=dynamic_lookup
 $ ln -s ./target/debug/libmy_module.dylib ./my_module.so
 $ lua5.3 -e 'require("my_module").hello("world")'
 hello, world!
 ```
 
+On macOS, you need to set additional linker arguments. One option is to compile with `cargo rustc --release -- -C link-arg=-undefined -C link-arg=dynamic_lookup`, the other is to create a `.cargo/config` with the following content:
+``` toml
+[target.x86_64-apple-darwin]
+rustflags = [
+  "-C", "link-arg=-undefined",
+  "-C", "link-arg=dynamic_lookup",
+]
+
+[target.aarch64-apple-darwin]
+rustflags = [
+  "-C", "link-arg=-undefined",
+  "-C", "link-arg=dynamic_lookup",
+]
+```
+On Linux you can build modules normally with `cargo build --release`.
+Vendored and non-vendored builds are supported for these OS.
+
+On Windows `vendored` mode for modules is not supported since you need to link to a Lua dll.
+Easiest way is to use either MinGW64 (as part of [MSYS2](https://github.com/msys2/msys2) package) with `pkg-config` or
+MSVC with `LUA_INC` / `LUA_LIB` / `LUA_LIB_NAME` environment variables.
+
+More details about compiling and linking Lua modules can be found on the [Building Modules](http://lua-users.org/wiki/BuildingModules) page.
+
 ## Safety
 
 One of the `mlua` goals is to provide *safe* API between Rust and Lua.
-Every place where the Lua C API may trigger an error longjmp
-in any way is protected by `lua_pcall` , and the user of the library is protected
-from directly interacting with unsafe things like the Lua stack, and there is
-overhead associated with this safety.
+Every place where the Lua C API may trigger an error longjmp in any way is protected by `lua_pcall`,
+and the user of the library is protected from directly interacting with unsafe things like the Lua stack,
+and there is overhead associated with this safety.
 
 Unfortunately, `mlua` does not provide absolute safety even without using `unsafe` .
-This library contains a huge amount of unsafe code. There are almost
-certainly bugs still lurking in this library!  It is surprisingly, fiendishly
-difficult to use the Lua C API without the potential for unsafety.
+This library contains a huge amount of unsafe code. There are almost certainly bugs still lurking in this library!
+It is surprisingly, fiendishly difficult to use the Lua C API without the potential for unsafety.
 
 ## Panic handling
 
@@ -149,10 +217,9 @@ let _ = lua.load(r#"
 unreachable!()
 ```
 
-`mlua` should also be panic safe in another way as well, which is that any `Lua`
-instances or handles remains usable after a user generated panic, and such
-panics should not break internal invariants or leak Lua stack space. This is
-mostly important to safely use `mlua` types in Drop impls, as you should not be
+`mlua` should also be panic safe in another way as well, which is that any `Lua` instances or handles
+remains usable after a user generated panic, and such panics should not break internal invariants or
+leak Lua stack space. This is mostly important to safely use `mlua` types in Drop impls, as you should not be
 using panics for general error handling.
 
 Below is a list of `mlua` behaviors that should be considered a bug.

benches/benchmark.rs

@@ -1,22 +1,22 @@
-#![cfg_attr(
-    all(feature = "luajit", target_os = "macos", target_arch = "x86_64"),
-    feature(link_args)
-)]
-
-#[cfg_attr(
-    all(feature = "luajit", target_os = "macos", target_arch = "x86_64"),
-    link_args = "-pagezero_size 10000 -image_base 100000000"
-)]
-extern "system" {}
-
 use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
+use std::time::Duration;
+use tokio::runtime::Runtime;
+use tokio::task;
+
 use mlua::prelude::*;
 
+fn collect_gc_twice(lua: &Lua) {
+    lua.gc_collect().unwrap();
+    lua.gc_collect().unwrap();
+}
+
 fn create_table(c: &mut Criterion) {
-    c.bench_function("create table", |b| {
-        b.iter_batched_ref(
-            || Lua::new(),
-            |lua| {
+    let lua = Lua::new();
+
+    c.bench_function("create [table empty]", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
                 lua.create_table().unwrap();
             },
             BatchSize::SmallInput,
@@ -25,12 +25,14 @@ fn create_table(c: &mut Criterion) {
 }
 
 fn create_array(c: &mut Criterion) {
-    c.bench_function("create array 10", |b| {
-        b.iter_batched_ref(
-            || Lua::new(),
-            |lua| {
+    let lua = Lua::new();
+
+    c.bench_function("create [array] 10", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
                 let table = lua.create_table().unwrap();
-                for i in 1..11 {
+                for i in 1..=10 {
                     table.set(i, i).unwrap();
                 }
             },
@@ -40,10 +42,12 @@ fn create_array(c: &mut Criterion) {
 }
 
 fn create_string_table(c: &mut Criterion) {
-    c.bench_function("create string table 10", |b| {
-        b.iter_batched_ref(
-            || Lua::new(),
-            |lua| {
+    let lua = Lua::new();
+
+    c.bench_function("create [table string] 10", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
                 let table = lua.create_table().unwrap();
                 for &s in &["1", "2", "3", "4", "5", "6", "7", "8", "9", "10"] {
                     let s = lua.create_string(s).unwrap();
@@ -55,30 +59,20 @@ fn create_string_table(c: &mut Criterion) {
     });
 }
 
-fn call_add_function(c: &mut Criterion) {
-    c.bench_function("call add function 3 10", |b| {
+fn call_lua_function(c: &mut Criterion) {
+    let lua = Lua::new();
+
+    c.bench_function("call Lua function [sum] 3 10", |b| {
         b.iter_batched_ref(
             || {
-                let lua = Lua::new();
-                let f = {
-                    let f: LuaFunction = lua
-                        .load(
-                            r#"
-                                function(a, b, c)
-                                    return a + b + c
-                                end
-                            "#,
-                        )
-                        .eval()
-                        .unwrap();
-                    lua.create_registry_value(f).unwrap()
-                };
-                (lua, f)
+                collect_gc_twice(&lua);
+                lua.load("function(a, b, c) return a + b + c end")
+                    .eval::<LuaFunction>()
+                    .unwrap()
             },
-            |(lua, f)| {
-                let add_function: LuaFunction = lua.registry_value(f).unwrap();
+            |function| {
                 for i in 0..10 {
-                    let _result: i64 = add_function.call((i, i + 1, i + 2)).unwrap();
+                    let _result: i64 = function.call((i, i + 1, i + 2)).unwrap();
                 }
             },
             BatchSize::SmallInput,
@@ -86,72 +80,75 @@ fn call_add_function(c: &mut Criterion) {
     });
 }
 
-fn call_add_callback(c: &mut Criterion) {
-    c.bench_function("call callback add 2 10", |b| {
+fn call_sum_callback(c: &mut Criterion) {
+    let lua = Lua::new();
+    let callback = lua
+        .create_function(|_, (a, b, c): (i64, i64, i64)| Ok(a + b + c))
+        .unwrap();
+    lua.globals().set("callback", callback).unwrap();
+
+    c.bench_function("call Rust callback [sum] 3 10", |b| {
         b.iter_batched_ref(
             || {
-                let lua = Lua::new();
-                let f = {
-                    let c: LuaFunction = lua
-                        .create_function(|_, (a, b, c): (i64, i64, i64)| Ok(a + b + c))
-                        .unwrap();
-                    lua.globals().set("callback", c).unwrap();
-                    let f: LuaFunction = lua
-                        .load(
-                            r#"
-                            function()
-                                for i = 1,10 do
-                                    callback(i, i, i)
-                                end
-                            end
-                        "#,
-                        )
-                        .eval()
-                        .unwrap();
-                    lua.create_registry_value(f).unwrap()
-                };
-                (lua, f)
+                collect_gc_twice(&lua);
+                lua.load("function() for i = 1,10 do callback(i, i+1, i+2) end end")
+                    .eval::<LuaFunction>()
+                    .unwrap()
             },
-            |(lua, f)| {
-                let entry_function: LuaFunction = lua.registry_value(f).unwrap();
-                entry_function.call::<_, ()>(()).unwrap();
+            |function| {
+                function.call::<_, ()>(()).unwrap();
             },
             BatchSize::SmallInput,
         );
     });
 }
 
-fn call_append_callback(c: &mut Criterion) {
-    c.bench_function("call callback append 10", |b| {
+fn call_async_sum_callback(c: &mut Criterion) {
+    let lua = Lua::new();
+    let callback = lua
+        .create_async_function(|_, (a, b, c): (i64, i64, i64)| async move {
+            task::yield_now().await;
+            Ok(a + b + c)
+        })
+        .unwrap();
+    lua.globals().set("callback", callback).unwrap();
+
+    c.bench_function("call async Rust callback [sum] 3 10", |b| {
+        let rt = Runtime::new().unwrap();
+        b.to_async(rt).iter_batched(
+            || {
+                collect_gc_twice(&lua);
+                lua.load("function() for i = 1,10 do callback(i, i+1, i+2) end end")
+                    .eval::<LuaFunction>()
+                    .unwrap()
+            },
+            |function| async move {
+                function.call_async::<_, ()>(()).await.unwrap();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn call_concat_callback(c: &mut Criterion) {
+    let lua = Lua::new();
+    let callback = lua
+        .create_function(|_, (a, b): (LuaString, LuaString)| {
+            Ok(format!("{}{}", a.to_str()?, b.to_str()?))
+        })
+        .unwrap();
+    lua.globals().set("callback", callback).unwrap();
+
+    c.bench_function("call Rust callback [concat string] 10", |b| {
         b.iter_batched_ref(
             || {
-                let lua = Lua::new();
-                let f = {
-                    let c: LuaFunction = lua
-                        .create_function(|_, (a, b): (LuaString, LuaString)| {
-                            Ok(format!("{}{}", a.to_str()?, b.to_str()?))
-                        })
-                        .unwrap();
-                    lua.globals().set("callback", c).unwrap();
-                    let f: LuaFunction = lua
-                        .load(
-                            r#"
-                            function()
-                                for _ = 1,10 do
-                                    callback("a", "b")
-                                end
-                            end
-                        "#,
-                        )
-                        .eval()
-                        .unwrap();
-                    lua.create_registry_value(f).unwrap()
-                };
-                (lua, f)
+                collect_gc_twice(&lua);
+                lua.load("function() for i = 1,10 do callback('a', tostring(i)) end end")
+                    .eval::<LuaFunction>()
+                    .unwrap()
             },
-            |(lua, f)| {
-                let entry_function: LuaFunction = lua.registry_value(f).unwrap();
-                entry_function.call::<_, ()>(()).unwrap();
+            |function| {
+                function.call::<_, ()>(()).unwrap();
             },
             BatchSize::SmallInput,
         );
@@ -159,10 +156,12 @@ fn call_append_callback(c: &mut Criterion) {
 }
 
 fn create_registry_values(c: &mut Criterion) {
-    c.bench_function("create registry 10", |b| {
-        b.iter_batched_ref(
-            || Lua::new(),
-            |lua| {
+    let lua = Lua::new();
+
+    c.bench_function("create [registry value] 10", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
                 for _ in 0..10 {
                     lua.create_registry_value(lua.pack(true).unwrap()).unwrap();
                 }
@@ -177,10 +176,12 @@ fn create_userdata(c: &mut Criterion) {
     struct UserData(i64);
     impl LuaUserData for UserData {}
 
-    c.bench_function("create userdata 10", |b| {
-        b.iter_batched_ref(
-            || Lua::new(),
-            |lua| {
+    let lua = Lua::new();
+
+    c.bench_function("create [table userdata] 10", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
                 let table: LuaTable = lua.create_table().unwrap();
                 for i in 1..11 {
                     table.set(i, UserData(i)).unwrap();
@@ -191,20 +192,80 @@ fn create_userdata(c: &mut Criterion) {
     });
 }
 
+fn call_userdata_method(c: &mut Criterion) {
+    struct UserData(i64);
+    impl LuaUserData for UserData {
+        fn add_methods<'lua, M: LuaUserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_method("method", |_, this, ()| Ok(this.0));
+        }
+    }
+
+    let lua = Lua::new();
+    lua.globals().set("userdata", UserData(10)).unwrap();
+
+    c.bench_function("call [userdata method] 10", |b| {
+        b.iter_batched_ref(
+            || {
+                collect_gc_twice(&lua);
+                lua.load("function() for i = 1,10 do userdata:method() end end")
+                    .eval::<LuaFunction>()
+                    .unwrap()
+            },
+            |function| {
+                function.call::<_, ()>(()).unwrap();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn call_async_userdata_method(c: &mut Criterion) {
+    #[derive(Clone, Copy)]
+    struct UserData(i64);
+    impl LuaUserData for UserData {
+        fn add_methods<'lua, M: LuaUserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_async_method("method", |_, this, ()| async move { Ok(this.0) });
+        }
+    }
+
+    let lua = Lua::new();
+    lua.globals().set("userdata", UserData(10)).unwrap();
+
+    c.bench_function("call async [userdata method] 10", |b| {
+        let rt = Runtime::new().unwrap();
+        b.to_async(rt).iter_batched(
+            || {
+                collect_gc_twice(&lua);
+                lua.load("function() for i = 1,10 do userdata:method() end end")
+                    .eval::<LuaFunction>()
+                    .unwrap()
+            },
+            |function| async move {
+                function.call_async::<_, ()>(()).await.unwrap();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
 criterion_group! {
     name = benches;
     config = Criterion::default()
-        .sample_size(200)
+        .sample_size(300)
+        .measurement_time(Duration::from_secs(10))
         .noise_threshold(0.02);
     targets =
         create_table,
         create_array,
         create_string_table,
-        call_add_function,
-        call_add_callback,
-        call_append_callback,
+        call_lua_function,
+        call_sum_callback,
+        call_async_sum_callback,
+        call_concat_callback,
         create_registry_values,
         create_userdata,
+        call_userdata_method,
+        call_async_userdata_method,
 }
 
 criterion_main!(benches);

build/find_dummy.rs

@@ -0,0 +1,5 @@
+use std::path::PathBuf;
+
+pub fn probe_lua() -> PathBuf {
+    unreachable!()
+}

build/find_normal.rs

@@ -1,106 +1,119 @@
 use std::env;
-use std::ffi::OsString;
-use std::fs::File;
-use std::io::{BufRead, BufReader, Result};
 use std::ops::Bound;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
+
+fn get_env_var(name: &str) -> String {
+    match env::var(name) {
+        Ok(val) => val,
+        Err(env::VarError::NotPresent) => String::new(),
+        Err(err) => panic!("cannot get {}: {}", name, err),
+    }
+}
 
 pub fn probe_lua() -> PathBuf {
-    let include_dir = env::var_os("LUA_INC").unwrap_or(OsString::new());
-    let lib_dir = env::var_os("LUA_LIB").unwrap_or(OsString::new());
-    let lua_lib = env::var_os("LUA_LIB_NAME").unwrap_or(OsString::new());
+    let include_dir = get_env_var("LUA_INC");
+    let lib_dir = get_env_var("LUA_LIB");
+    let lua_lib = get_env_var("LUA_LIB_NAME");
 
     println!("cargo:rerun-if-env-changed=LUA_INC");
     println!("cargo:rerun-if-env-changed=LUA_LIB");
     println!("cargo:rerun-if-env-changed=LUA_LIB_NAME");
     println!("cargo:rerun-if-env-changed=LUA_LINK");
 
-    if include_dir != "" && lib_dir != "" && lua_lib != "" {
-        let _version = use_custom_lua(&include_dir, &lib_dir, &lua_lib).unwrap();
+    let need_lua_lib = cfg!(any(not(feature = "module"), target_os = "windows"));
+
+    if include_dir != "" {
+        if need_lua_lib {
+            if lib_dir == "" {
+                panic!("LUA_LIB is not set");
+            }
+            if lua_lib == "" {
+                panic!("LUA_LIB_NAME is not set");
+            }
+
+            let mut link_lib = "";
+            if get_env_var("LUA_LINK") == "static" {
+                link_lib = "static=";
+            };
+            println!("cargo:rustc-link-search=native={}", lib_dir);
+            println!("cargo:rustc-link-lib={}{}", link_lib, lua_lib);
+        }
         return PathBuf::from(include_dir);
     }
 
-    // Find using via pkg-config
+    // Find using `pkg-config`
+
+    #[cfg(feature = "lua54")]
+    {
+        let mut lua = pkg_config::Config::new()
+            .range_version((Bound::Included("5.4"), Bound::Excluded("5.5")))
+            .cargo_metadata(need_lua_lib)
+            .probe("lua");
+
+        if lua.is_err() {
+            lua = pkg_config::Config::new()
+                .cargo_metadata(need_lua_lib)
+                .probe("lua5.4");
+        }
+
+        lua.unwrap().include_paths[0].clone()
+    }
 
     #[cfg(feature = "lua53")]
     {
         let mut lua = pkg_config::Config::new()
             .range_version((Bound::Included("5.3"), Bound::Excluded("5.4")))
+            .cargo_metadata(need_lua_lib)
             .probe("lua");
 
         if lua.is_err() {
-            lua = pkg_config::Config::new().probe("lua5.3");
+            lua = pkg_config::Config::new()
+                .cargo_metadata(need_lua_lib)
+                .probe("lua5.3");
         }
 
-        return lua.unwrap().include_paths[0].clone();
+        lua.unwrap().include_paths[0].clone()
     }
 
     #[cfg(feature = "lua52")]
     {
         let mut lua = pkg_config::Config::new()
             .range_version((Bound::Included("5.2"), Bound::Excluded("5.3")))
+            .cargo_metadata(need_lua_lib)
             .probe("lua");
 
         if lua.is_err() {
-            lua = pkg_config::Config::new().probe("lua5.2");
+            lua = pkg_config::Config::new()
+                .cargo_metadata(need_lua_lib)
+                .probe("lua5.2");
         }
 
-        return lua.unwrap().include_paths[0].clone();
+        lua.unwrap().include_paths[0].clone()
     }
 
     #[cfg(feature = "lua51")]
     {
         let mut lua = pkg_config::Config::new()
             .range_version((Bound::Included("5.1"), Bound::Excluded("5.2")))
+            .cargo_metadata(need_lua_lib)
             .probe("lua");
 
         if lua.is_err() {
-            lua = pkg_config::Config::new().probe("lua5.1");
+            lua = pkg_config::Config::new()
+                .cargo_metadata(need_lua_lib)
+                .probe("lua5.1");
         }
 
-        return lua.unwrap().include_paths[0].clone();
+        lua.unwrap().include_paths[0].clone()
     }
 
     #[cfg(feature = "luajit")]
     {
         let lua = pkg_config::Config::new()
-            .range_version((Bound::Included("2.1.0"), Bound::Unbounded))
+            .range_version((Bound::Included("2.0.5"), Bound::Unbounded))
+            .cargo_metadata(need_lua_lib)
             .probe("luajit");
 
-        return lua.unwrap().include_paths[0].clone();
+        lua.unwrap().include_paths[0].clone()
     }
 }
-
-fn use_custom_lua<S: AsRef<Path>>(include_dir: &S, lib_dir: &S, lua_lib: &S) -> Result<String> {
-    let mut version_found = String::new();
-
-    // Find LUA_VERSION_NUM
-    let mut lua_h_path = include_dir.as_ref().to_owned();
-    lua_h_path.push("lua.h");
-    let f = File::open(lua_h_path)?;
-    let reader = BufReader::new(f);
-    for line in reader.lines() {
-        let line = line?;
-        let parts = line.split_whitespace().collect::<Vec<_>>();
-        if parts.len() == 3 && parts[1] == "LUA_VERSION_NUM" {
-            version_found = parts[2].to_string();
-        }
-    }
-
-    let mut link_lib = String::new();
-    if env::var("LUA_LINK").unwrap_or(String::new()) == "static" {
-        link_lib = "static=".to_string();
-    }
-
-    println!(
-        "cargo:rustc-link-search=native={}",
-        lib_dir.as_ref().display()
-    );
-    println!(
-        "cargo:rustc-link-lib={}{}",
-        link_lib,
-        lua_lib.as_ref().display()
-    );
-
-    Ok(version_found)
-}

build/find_vendored.rs

@@ -1,11 +1,8 @@
 use std::path::PathBuf;
 
-#[cfg(any(feature = "lua53", feature = "lua52", feature = "lua51"))]
-use lua_src;
-#[cfg(feature = "luajit")]
-use luajit_src;
-
 pub fn probe_lua() -> PathBuf {
+    #[cfg(feature = "lua54")]
+    let artifacts = lua_src::Build::new().build(lua_src::Lua54);
     #[cfg(feature = "lua53")]
     let artifacts = lua_src::Build::new().build(lua_src::Lua53);
     #[cfg(feature = "lua52")]
@@ -15,6 +12,8 @@ pub fn probe_lua() -> PathBuf {
     #[cfg(feature = "luajit")]
     let artifacts = luajit_src::Build::new().build();
 
+    #[cfg(not(feature = "module"))]
     artifacts.print_cargo_metadata();
+
     artifacts.include_dir().to_owned()
 }

build/main.rs

@@ -1,12 +1,47 @@
 #![allow(unreachable_code)]
 
 use std::env;
-use std::io::{Error, ErrorKind, Result};
+use std::fs::File;
+use std::io::{Error, ErrorKind, Result, Write};
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
-#[cfg_attr(feature = "vendored", path = "find_vendored.rs")]
-#[cfg_attr(not(feature = "vendored"), path = "find_normal.rs")]
+#[cfg_attr(
+    all(
+        feature = "vendored",
+        any(
+            feature = "lua54",
+            feature = "lua53",
+            feature = "lua52",
+            feature = "lua51",
+            feature = "luajit"
+        )
+    ),
+    path = "find_vendored.rs"
+)]
+#[cfg_attr(
+    all(
+        not(feature = "vendored"),
+        any(
+            feature = "lua54",
+            feature = "lua53",
+            feature = "lua52",
+            feature = "lua51",
+            feature = "luajit"
+        )
+    ),
+    path = "find_normal.rs"
+)]
+#[cfg_attr(
+    not(any(
+        feature = "lua54",
+        feature = "lua53",
+        feature = "lua52",
+        feature = "lua51",
+        feature = "luajit"
+    )),
+    path = "find_dummy.rs"
+)]
 mod find;
 
 trait CommandExt {
@@ -57,30 +92,152 @@ fn build_glue<P: AsRef<Path> + std::fmt::Debug>(include_path: &P) {
         .unwrap();
 }
 
+// When cross-compiling, we cannot use `build_glue` as we cannot run the generated
+// executable.  Instead, let's take a stab at synthesizing the likely values.
+// If you're cross-compiling and using a non-vendored library then there is a chance
+// that the values selected here may be incorrect, but we have no way to determine
+// that here.
+fn generate_glue() -> Result<()> {
+    let build_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let mut glue = File::create(build_dir.join("glue.rs"))?;
+    writeln!(
+        glue,
+        "/* This file was generated by build/main.rs; do not modify by hand */"
+    )?;
+    writeln!(glue, "use std::os::raw::*;")?;
+
+    writeln!(glue, "/* luaconf.h */")?;
+    let pointer_bit_width: usize = env::var("CARGO_CFG_TARGET_POINTER_WIDTH")
+        .unwrap()
+        .parse()
+        .unwrap();
+    writeln!(
+        glue,
+        "pub const LUA_EXTRASPACE: c_int = {} / 8;",
+        pointer_bit_width
+    )?;
+
+    // This is generally hardcoded to this size
+    writeln!(glue, "pub const LUA_IDSIZE: c_int = 60;")?;
+
+    // Unless the target is restricted, the defaults are 64 bit
+    writeln!(glue, "pub type LUA_NUMBER = c_double;")?;
+    writeln!(glue, "pub type LUA_INTEGER = i64;")?;
+    writeln!(glue, "pub type LUA_UNSIGNED = u64;")?;
+
+    writeln!(glue, "/* lua.h */")?;
+    let version = if cfg!(any(feature = "luajit", feature = "lua51")) {
+        (5, 1, 0)
+    } else if cfg!(feature = "lua52") {
+        (5, 2, 0)
+    } else if cfg!(feature = "lua53") {
+        (5, 3, 0)
+    } else if cfg!(feature = "lua54") {
+        (5, 4, 0)
+    } else {
+        unreachable!();
+    };
+    writeln!(
+        glue,
+        "pub const LUA_VERSION_NUM: c_int = {};",
+        (version.0 * 100) + version.1
+    )?;
+
+    let max_stack = if pointer_bit_width >= 32 {
+        1_000_000
+    } else {
+        15_000
+    };
+    writeln!(
+        glue,
+        "pub const LUA_REGISTRYINDEX: c_int = -{} - 1000;",
+        max_stack
+    )?;
+
+    // These two are only defined in lua 5.1
+    writeln!(glue, "pub const LUA_ENVIRONINDEX: c_int = -10001;")?;
+    writeln!(glue, "pub const LUA_GLOBALSINDEX: c_int = -10002;")?;
+
+    writeln!(glue, "/* lauxlib.h */")?;
+    // This is only defined in lua 5.3 and up, but we can always generate its value here,
+    // even if we don't use it.
+    // This matches the default definition in lauxlib.h
+    writeln!(glue, "pub const LUAL_NUMSIZES: c_int = std::mem::size_of::<LUA_INTEGER>() as c_int * 16 + std::mem::size_of::<LUA_NUMBER>() as c_int;")?;
+
+    writeln!(glue, "/* lualib.h */")?;
+    write!(
+        glue,
+        r#"
+#[cfg(feature = "luajit")]
+pub const LUA_BITLIBNAME: &str = "bit";
+#[cfg(not(feature = "luajit"))]
+pub const LUA_BITLIBNAME: &str = "bit32";
+
+pub const LUA_COLIBNAME: &str = "coroutine";
+pub const LUA_DBLIBNAME: &str = "debug";
+pub const LUA_IOLIBNAME: &str = "io";
+pub const LUA_LOADLIBNAME: &str = "package";
+pub const LUA_MATHLIBNAME: &str = "math";
+pub const LUA_OSLIBNAME: &str = "os";
+pub const LUA_STRLIBNAME: &str = "string";
+pub const LUA_TABLIBNAME: &str = "table";
+pub const LUA_UTF8LIBNAME: &str = "utf8";
+
+pub const LUA_JITLIBNAME: &str = "jit";
+pub const LUA_FFILIBNAME: &str = "ffi";
+"#
+    )?;
+
+    Ok(())
+}
+
 fn main() {
     #[cfg(not(any(
+        feature = "lua54",
         feature = "lua53",
         feature = "lua52",
         feature = "lua51",
         feature = "luajit"
     )))]
-    panic!("You must enable one of the features: lua53, lua52, lua51, luajit");
+    compile_error!("You must enable one of the features: lua54, lua53, lua52, lua51, luajit");
+
+    #[cfg(all(
+        feature = "lua54",
+        any(
+            feature = "lua53",
+            feature = "lua52",
+            feature = "lua51",
+            feature = "luajit"
+        )
+    ))]
+    compile_error!("You can enable only one of the features: lua54, lua53, lua52, lua51, luajit");
 
     #[cfg(all(
         feature = "lua53",
         any(feature = "lua52", feature = "lua51", feature = "luajit")
     ))]
-    panic!("You can enable only one of the features: lua53, lua52, lua51, luajit");
+    compile_error!("You can enable only one of the features: lua54, lua53, lua52, lua51, luajit");
 
     #[cfg(all(feature = "lua52", any(feature = "lua51", feature = "luajit")))]
-    panic!("You can enable only one of the features: lua53, lua52, lua51, luajit");
+    compile_error!("You can enable only one of the features: lua54, lua53, lua52, lua51, luajit");
 
     #[cfg(all(feature = "lua51", feature = "luajit"))]
-    panic!("You can enable only one of the features: lua53, lua52, lua51, luajit");
+    compile_error!("You can enable only one of the features: lua54, lua53, lua52, lua51, luajit");
 
-    #[cfg(all(feature = "lua51", feature = "luajit"))]
-    panic!("You can enable only one of the features: lua53, lua52, lua51, luajit");
+    // We don't support "vendored module" mode on windows
+    #[cfg(all(feature = "vendored", feature = "module", target_os = "windows"))]
+    compile_error!(
+        "Vendored (static) builds are not supported for modules on Windows.\n"
+            + "Please, use `pkg-config` or custom mode to link to a Lua dll."
+    );
 
     let include_dir = find::probe_lua();
-    build_glue(&include_dir);
+    if env::var("TARGET").unwrap() != env::var("HOST").unwrap() {
+        generate_glue().unwrap();
+    } else {
+        build_glue(&include_dir);
+        println!("cargo:rerun-if-changed=src/ffi/glue/glue.c");
+    }
+
+    println!("cargo:rerun-if-changed=build");
 }

examples/async_http_client.rs

@@ -1,28 +1,28 @@
-use std::cell::RefCell;
 use std::collections::HashMap;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use bstr::BString;
-use hyper::{body::Body as HyperBody, Client as HyperClient};
-use tokio::stream::StreamExt;
+use hyper::body::{Body as HyperBody, HttpBody as _};
+use hyper::Client as HyperClient;
+use tokio::sync::Mutex;
 
 use mlua::{Error, Lua, Result, UserData, UserDataMethods};
 
 #[derive(Clone)]
-struct BodyReader(Rc<RefCell<HyperBody>>);
+struct BodyReader(Arc<Mutex<HyperBody>>);
 
 impl BodyReader {
     fn new(body: HyperBody) -> Self {
-        BodyReader(Rc::new(RefCell::new(body)))
+        BodyReader(Arc::new(Mutex::new(body)))
     }
 }
 
 impl UserData for BodyReader {
     fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
         methods.add_async_method("read", |_, reader, ()| async move {
-            let mut reader = reader.0.borrow_mut();
-            let bytes = reader.try_next().await.map_err(Error::external)?;
-            if let Some(bytes) = bytes {
+            let mut reader = reader.0.lock().await;
+            if let Some(bytes) = reader.data().await {
+                let bytes = bytes.map_err(Error::external)?;
                 return Ok(Some(BString::from(bytes.as_ref())));
             }
             Ok(None)
@@ -62,7 +62,7 @@ async fn main() -> Result<()> {
     let f = lua
         .load(
             r#"
-            local res = fetch_url(...);
+            local res = fetch_url(...)
             print(res.status)
             for key, vals in pairs(res.headers) do
                 for _, val in ipairs(vals) do

examples/async_http_reqwest.rs

@@ -0,0 +1,41 @@
+use mlua::{Error, Lua, LuaSerdeExt, Result};
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let lua = Lua::new();
+    let globals = lua.globals();
+    globals.set("null", lua.null()?)?;
+
+    let fetch_json = lua.create_async_function(|lua, uri: String| async move {
+        let resp = reqwest::get(&uri)
+            .await
+            .and_then(|resp| resp.error_for_status())
+            .map_err(Error::external)?;
+        let json = resp
+            .json::<serde_json::Value>()
+            .await
+            .map_err(Error::external)?;
+        lua.to_value(&json)
+    })?;
+    globals.set("fetch_json", fetch_json)?;
+
+    let f = lua
+        .load(
+            r#"
+            function print_r(t, indent)
+                local indent = indent or ''
+                for k, v in pairs(t) do
+                    io.write(indent, tostring(k))
+                    if type(v) == "table" then io.write(':\n') print_r(v, indent..'  ')
+                    else io.write(': ', v == null and "null" or tostring(v), '\n') end
+                end
+            end
+
+            local res = fetch_json(...)
+            print_r(res)
+        "#,
+        )
+        .into_function()?;
+
+    f.call_async("https://httpbin.org/anything?arg0=val0").await
+}

examples/async_http_server.rs

@@ -0,0 +1,101 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use hyper::server::conn::AddrStream;
+use hyper::service::{make_service_fn, service_fn};
+use hyper::{Body, Request, Response, Server};
+
+use mlua::{Error, Function, Lua, Result, Table, UserData, UserDataMethods};
+
+#[derive(Clone)]
+struct LuaRequest(Arc<(SocketAddr, Request<Body>)>);
+
+impl UserData for LuaRequest {
+    fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+        methods.add_method("remote_addr", |_lua, req, ()| Ok((req.0).0.to_string()));
+        methods.add_method("method", |_lua, req, ()| Ok((req.0).1.method().to_string()));
+    }
+}
+
+async fn run_server(handler: Function<'static>) -> Result<()> {
+    let make_svc = make_service_fn(|socket: &AddrStream| {
+        let remote_addr = socket.remote_addr();
+        let handler = handler.clone();
+        async move {
+            Ok::<_, Error>(service_fn(move |req: Request<Body>| {
+                let handler = handler.clone();
+                async move {
+                    let lua_req = LuaRequest(Arc::new((remote_addr, req)));
+                    let lua_resp: Table = handler.call_async(lua_req).await?;
+                    let body = lua_resp
+                        .get::<_, Option<String>>("body")?
+                        .unwrap_or_default();
+
+                    let mut resp = Response::builder()
+                        .status(lua_resp.get::<_, Option<u16>>("status")?.unwrap_or(200));
+
+                    if let Some(headers) = lua_resp.get::<_, Option<Table>>("headers")? {
+                        for pair in headers.pairs::<String, String>() {
+                            let (h, v) = pair?;
+                            resp = resp.header(&h, v);
+                        }
+                    }
+
+                    Ok::<_, Error>(resp.body(Body::from(body)).unwrap())
+                }
+            }))
+        }
+    });
+
+    let addr = ([127, 0, 0, 1], 3000).into();
+    let server = Server::bind(&addr).executor(LocalExec).serve(make_svc);
+
+    println!("Listening on http://{}", addr);
+
+    tokio::task::LocalSet::new()
+        .run_until(server)
+        .await
+        .map_err(Error::external)
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let lua = Lua::new().into_static();
+
+    let handler: Function = lua
+        .load(
+            r#"
+        function(req)
+            return {
+                status = 200,
+                headers = {
+                    ["X-Req-Method"] = req:method(),
+                    ["X-Remote-Addr"] = req:remote_addr(),
+                },
+                body = "Hello, World!"
+            }
+        end
+    "#,
+        )
+        .eval()?;
+
+    run_server(handler).await?;
+
+    // Consume the static reference and drop it.
+    // This is safe as long as we don't hold any other references to Lua
+    // or alive resources.
+    unsafe { Lua::from_static(lua) };
+    Ok(())
+}
+
+#[derive(Clone, Copy, Debug)]
+struct LocalExec;
+
+impl<F> hyper::rt::Executor<F> for LocalExec
+where
+    F: std::future::Future + 'static, // not requiring `Send`
+{
+    fn execute(&self, fut: F) {
+        tokio::task::spawn_local(fut);
+    }
+}

examples/async_tcp_server.rs

@@ -1,10 +1,9 @@
-use std::cell::RefCell;
-use std::net::Shutdown;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use bstr::BString;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::{TcpListener, TcpStream};
-use tokio::prelude::*;
+use tokio::sync::Mutex;
 use tokio::task;
 
 use mlua::{Function, Lua, Result, UserData, UserDataMethods};
@@ -13,16 +12,16 @@ use mlua::{Function, Lua, Result, UserData, UserDataMethods};
 struct LuaTcp;
 
 #[derive(Clone)]
-struct LuaTcpListener(Rc<RefCell<TcpListener>>);
+struct LuaTcpListener(Arc<Mutex<TcpListener>>);
 
 #[derive(Clone)]
-struct LuaTcpStream(Rc<RefCell<TcpStream>>);
+struct LuaTcpStream(Arc<Mutex<TcpStream>>);
 
 impl UserData for LuaTcp {
     fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
         methods.add_async_function("bind", |_, addr: String| async move {
             let listener = TcpListener::bind(addr).await?;
-            Ok(LuaTcpListener(Rc::new(RefCell::new(listener))))
+            Ok(LuaTcpListener(Arc::new(Mutex::new(listener))))
         });
     }
 }
@@ -30,8 +29,8 @@ impl UserData for LuaTcp {
 impl UserData for LuaTcpListener {
     fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
         methods.add_async_method("accept", |_, listener, ()| async move {
-            let (stream, _) = listener.0.borrow_mut().accept().await?;
-            Ok(LuaTcpStream(Rc::new(RefCell::new(stream))))
+            let (stream, _) = listener.0.lock().await.accept().await?;
+            Ok(LuaTcpStream(Arc::new(Mutex::new(stream))))
         });
     }
 }
@@ -39,34 +38,31 @@ impl UserData for LuaTcpListener {
 impl UserData for LuaTcpStream {
     fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
         methods.add_async_method("peer_addr", |_, stream, ()| async move {
-            Ok(stream.0.borrow().peer_addr()?.to_string())
+            Ok(stream.0.lock().await.peer_addr()?.to_string())
         });
 
         methods.add_async_method("read", |_, stream, size: usize| async move {
             let mut buf = vec![0; size];
-            let n = stream.0.borrow_mut().read(&mut buf).await?;
+            let n = stream.0.lock().await.read(&mut buf).await?;
             buf.truncate(n);
             Ok(BString::from(buf))
         });
 
         methods.add_async_method("write", |_, stream, data: BString| async move {
-            let n = stream.0.borrow_mut().write(&data).await?;
+            let n = stream.0.lock().await.write(&data).await?;
             Ok(n)
         });
 
-        methods.add_method("close", |_, stream, ()| {
-            stream.0.borrow().shutdown(Shutdown::Both)?;
+        methods.add_async_method("close", |_, stream, ()| async move {
+            stream.0.lock().await.shutdown().await?;
             Ok(())
         });
     }
 }
 
-#[tokio::main]
-async fn main() -> Result<()> {
-    let lua = Lua::new();
-
+async fn run_server(lua: &'static Lua) -> Result<()> {
     let spawn = lua.create_function(move |_, func: Function| {
-        task::spawn_local(async move { func.call_async::<_, ()>(()).await.unwrap() });
+        task::spawn_local(async move { func.call_async::<_, ()>(()).await });
         Ok(())
     })?;
 
@@ -80,20 +76,33 @@ async fn main() -> Result<()> {
             local addr = ...
             local listener = tcp.bind(addr)
             print("listening on "..addr)
+
+            local accept_new = true
             while true do
                 local stream = listener:accept()
                 local peer_addr = stream:peer_addr()
                 print("connected from "..peer_addr)
+
+                if not accept_new then
+                    return
+                end
+
                 spawn(function()
                     while true do
                         local data = stream:read(100)
                         data = data:match("^%s*(.-)%s*$") -- trim
                         print("["..peer_addr.."] "..data)
-                        stream:write("got: "..data.."\n")
+                        if data == "bye" then
+                            stream:write("bye bye\n")
+                            stream:close()
+                            return
+                        end
                         if data == "exit" then
                             stream:close()
-                            break
+                            accept_new = false
+                            return
                         end
+                        stream:write("echo: "..data.."\n")
                     end
                 end)
             end
@@ -105,3 +114,15 @@ async fn main() -> Result<()> {
         .run_until(server.call_async::<_, ()>("0.0.0.0:1234"))
         .await
 }
+
+#[tokio::main]
+async fn main() {
+    let lua = Lua::new().into_static();
+
+    run_server(lua).await.unwrap();
+
+    // Consume the static reference and drop it.
+    // This is safe as long as we don't hold any other references to Lua
+    // or alive resources.
+    unsafe { Lua::from_static(lua) };
+}

examples/guided_tour.rs

@@ -164,6 +164,33 @@ fn main() -> Result<()> {
             < f32::EPSILON
     );
 
+    // Normally, Rust types passed to `Lua` must be `'static`, because there is no way to be
+    // sure of their lifetime inside the Lua state. There is, however, a limited way to lift this
+    // requirement. You can call `Lua::scope` to create userdata and callbacks types that only live
+    // for as long as the call to scope, but do not have to be `'static` (and `Send`).
+
+    {
+        let mut rust_val = 0;
+
+        lua.scope(|scope| {
+            // We create a 'sketchy' Lua callback that holds a mutable reference to the variable
+            // `rust_val`.  Outside of a `Lua::scope` call, this would not be allowed
+            // because it could be unsafe.
+
+            lua.globals().set(
+                "sketchy",
+                scope.create_function_mut(|_, ()| {
+                    rust_val = 42;
+                    Ok(())
+                })?,
+            )?;
+
+            lua.load("sketchy()").exec()
+        })?;
+
+        assert_eq!(rust_val, 42);
+    }
+
     // We were able to run our 'sketchy' function inside the scope just fine.  However, if we
     // try to run our 'sketchy' function outside of the scope, the function we created will have
     // been invalidated and we will generate an error.  If our function wasn't invalidated, we

examples/module/.cargo/config

@@ -0,0 +1,5 @@
+[target.x86_64-apple-darwin]
+rustflags = [
+  "-C", "link-arg=-undefined",
+  "-C", "link-arg=dynamic_lookup",
+]

examples/module/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "rust_module"
+version = "0.0.0"
+authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
+edition = "2018"
+
+[lib]
+crate-type = ["cdylib"]
+
+[features]
+lua54 = ["mlua/lua54"]
+lua53 = ["mlua/lua53"]
+lua52 = ["mlua/lua52"]
+lua51 = ["mlua/lua51"]
+luajit = ["mlua/luajit"]
+vendored = ["mlua/vendored"]
+
+[dependencies]
+mlua = { path = "../..", features = ["module"] }

examples/module/src/lib.rs

@@ -0,0 +1,17 @@
+use mlua::prelude::*;
+
+fn sum(_: &Lua, (a, b): (i64, i64)) -> LuaResult<i64> {
+    Ok(a + b)
+}
+
+fn used_memory(lua: &Lua, _: ()) -> LuaResult<usize> {
+    Ok(lua.used_memory())
+}
+
+#[mlua::lua_module]
+fn rust_module(lua: &Lua) -> LuaResult<LuaTable> {
+    let exports = lua.create_table()?;
+    exports.set("sum", lua.create_function(sum)?)?;
+    exports.set("used_memory", lua.create_function(used_memory)?)?;
+    Ok(exports)
+}

examples/serialize.rs

@@ -0,0 +1,66 @@
+use mlua::{Error, Lua, LuaSerdeExt, Result, UserData, Value};
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize)]
+enum Transmission {
+    Manual,
+    Automatic,
+}
+
+#[derive(Serialize, Deserialize)]
+struct Engine {
+    v: u32,
+    kw: u32,
+}
+
+#[derive(Serialize, Deserialize)]
+struct Car {
+    active: bool,
+    model: String,
+    transmission: Transmission,
+    engine: Engine,
+}
+
+impl UserData for Car {}
+
+fn main() -> Result<()> {
+    let lua = Lua::new();
+    let globals = lua.globals();
+
+    // Create Car struct from a Lua table
+    let car: Car = lua.from_value(lua.load(r#"
+        {active = true, model = "Volkswagen Golf", transmission = "Automatic", engine = {v = 1499, kw = 90}}
+    "#).eval()?)?;
+
+    // Set it as (serializable) userdata
+    globals.set("null", lua.null()?)?;
+    globals.set("array_mt", lua.array_metatable()?)?;
+    globals.set("car", lua.create_ser_userdata(car)?)?;
+
+    // Create a Lua table with multiple data types
+    let val: Value = lua
+        .load(r#"{driver = "Boris", car = car, price = null, points = setmetatable({}, array_mt)}"#)
+        .eval()?;
+
+    // Serialize the table above to JSON
+    let json_str = serde_json::to_string(&val).map_err(Error::external)?;
+    println!("{}", json_str);
+
+    // Create Lua Value from JSON (or any serializable type)
+    let json = serde_json::json!({
+        "key": "value",
+        "null": null,
+        "array": [],
+    });
+    globals.set("json_value", lua.to_value(&json)?)?;
+    lua.load(
+        r#"
+        assert(json_value["key"] == "value")
+        assert(json_value["null"] == null)
+        assert(#(json_value["array"]) == 0)
+    "#,
+    )
+    .exec()?;
+
+    Ok(())
+}

mlua_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua_derive"
-version = "0.3.0"
+version = "0.5.0"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 edition = "2018"
 description = "Procedural macros for the mlua crate."

mlua_derive/src/lib.rs

@@ -21,6 +21,8 @@ pub fn lua_module(attr: TokenStream, item: TokenStream) -> TokenStream {
     let ext_entrypoint_name = Ident::new(&format!("luaopen_{}", item.sig.ident), Span::call_site());
 
     let wrapped = quote_spanned! { span =>
+        mlua::require_module_feature!();
+
         #[no_mangle]
         unsafe extern "C" fn #ext_entrypoint_name(state: *mut mlua::lua_State) -> std::os::raw::c_int {
             #item

src/conversion.rs

@@ -1,4 +1,5 @@
-use std::collections::{BTreeMap, HashMap};
+use std::borrow::Cow;
+use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
 use std::ffi::{CStr, CString};
 use std::hash::{BuildHasher, Hash};
 use std::string::String as StdString;
@@ -12,7 +13,7 @@ use crate::lua::Lua;
 use crate::string::String;
 use crate::table::Table;
 use crate::thread::Thread;
-use crate::types::{LightUserData, Number};
+use crate::types::{LightUserData, MaybeSend};
 use crate::userdata::{AnyUserData, UserData};
 use crate::value::{FromLua, Nil, ToLua, Value};
 
@@ -122,7 +123,7 @@ impl<'lua> FromLua<'lua> for AnyUserData<'lua> {
     }
 }
 
-impl<'lua, T: 'static + UserData> ToLua<'lua> for T {
+impl<'lua, T: 'static + MaybeSend + UserData> ToLua<'lua> for T {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         Ok(Value::UserData(lua.create_userdata(self)?))
     }
@@ -216,12 +217,18 @@ impl<'lua> FromLua<'lua> for StdString {
     }
 }
 
-impl<'lua, 'a> ToLua<'lua> for &'a str {
+impl<'lua> ToLua<'lua> for &str {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         Ok(Value::String(lua.create_string(self)?))
     }
 }
 
+impl<'lua> ToLua<'lua> for Cow<'_, str> {
+    fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+        Ok(Value::String(lua.create_string(self.as_bytes())?))
+    }
+}
+
 impl<'lua> ToLua<'lua> for CString {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         Ok(Value::String(lua.create_string(self.as_bytes())?))
@@ -250,13 +257,19 @@ impl<'lua> FromLua<'lua> for CString {
     }
 }
 
-impl<'lua, 'a> ToLua<'lua> for &'a CStr {
+impl<'lua> ToLua<'lua> for &CStr {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         Ok(Value::String(lua.create_string(self.to_bytes())?))
     }
 }
 
-impl<'lua, 'a> ToLua<'lua> for BString {
+impl<'lua> ToLua<'lua> for Cow<'_, CStr> {
+    fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+        Ok(Value::String(lua.create_string(self.to_bytes())?))
+    }
+}
+
+impl<'lua> ToLua<'lua> for BString {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         Ok(Value::String(lua.create_string(&self)?))
     }
@@ -278,7 +291,7 @@ impl<'lua> FromLua<'lua> for BString {
     }
 }
 
-impl<'lua, 'a> ToLua<'lua> for &BStr {
+impl<'lua> ToLua<'lua> for &BStr {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         Ok(Value::String(lua.create_string(&self)?))
     }
@@ -345,7 +358,13 @@ macro_rules! lua_convert_float {
     ($x:ty) => {
         impl<'lua> ToLua<'lua> for $x {
             fn to_lua(self, _: &'lua Lua) -> Result<Value<'lua>> {
-                Ok(Value::Number(self as Number))
+                cast(self)
+                    .ok_or_else(|| Error::ToLuaConversionError {
+                        from: stringify!($x),
+                        to: "number",
+                        message: Some("out of range".to_string()),
+                    })
+                    .map(Value::Number)
             }
         }
 
@@ -373,6 +392,50 @@ macro_rules! lua_convert_float {
 lua_convert_float!(f32);
 lua_convert_float!(f64);
 
+impl<'lua, T> ToLua<'lua> for &[T]
+where
+    T: Clone + ToLua<'lua>,
+{
+    fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+        Ok(Value::Table(
+            lua.create_sequence_from(self.iter().cloned())?,
+        ))
+    }
+}
+
+macro_rules! lua_convert_array {
+    ($($N:literal)+) => {
+        $(
+            impl<'lua, T> ToLua<'lua> for [T; $N]
+            where
+                T: Clone + ToLua<'lua>,
+            {
+                fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+                    (&self).to_lua(lua)
+                }
+            }
+
+            impl<'lua, T> ToLua<'lua> for &[T; $N]
+            where
+                T: Clone + ToLua<'lua>,
+            {
+                fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+                    Ok(Value::Table(
+                        lua.create_sequence_from(self.iter().cloned())?,
+                    ))
+                }
+            }
+        )+
+    }
+}
+
+lua_convert_array! {
+    0  1  2  3  4  5  6  7  8  9
+   10 11 12 13 14 15 16 17 18 19
+   20 21 22 23 24 25 26 27 28 29
+   30 31 32
+}
+
 impl<'lua, T: ToLua<'lua>> ToLua<'lua> for Vec<T> {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         Ok(Value::Table(lua.create_sequence_from(self)?))
@@ -437,6 +500,56 @@ impl<'lua, K: Ord + FromLua<'lua>, V: FromLua<'lua>> FromLua<'lua> for BTreeMap<
     }
 }
 
+impl<'lua, T: Eq + Hash + ToLua<'lua>, S: BuildHasher> ToLua<'lua> for HashSet<T, S> {
+    fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+        Ok(Value::Table(lua.create_table_from(
+            self.into_iter().map(|val| (val, true)),
+        )?))
+    }
+}
+
+impl<'lua, T: Eq + Hash + FromLua<'lua>, S: BuildHasher + Default> FromLua<'lua> for HashSet<T, S> {
+    fn from_lua(value: Value<'lua>, _: &'lua Lua) -> Result<Self> {
+        if let Value::Table(table) = value {
+            table
+                .pairs::<T, Value<'lua>>()
+                .map(|res| res.map(|(k, _)| k))
+                .collect()
+        } else {
+            Err(Error::FromLuaConversionError {
+                from: value.type_name(),
+                to: "HashSet",
+                message: Some("expected table".to_string()),
+            })
+        }
+    }
+}
+
+impl<'lua, T: Ord + ToLua<'lua>> ToLua<'lua> for BTreeSet<T> {
+    fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
+        Ok(Value::Table(lua.create_table_from(
+            self.into_iter().map(|val| (val, true)),
+        )?))
+    }
+}
+
+impl<'lua, T: Ord + FromLua<'lua>> FromLua<'lua> for BTreeSet<T> {
+    fn from_lua(value: Value<'lua>, _: &'lua Lua) -> Result<Self> {
+        if let Value::Table(table) = value {
+            table
+                .pairs::<T, Value<'lua>>()
+                .map(|res| res.map(|(k, _)| k))
+                .collect()
+        } else {
+            Err(Error::FromLuaConversionError {
+                from: value.type_name(),
+                to: "BTreeSet",
+                message: Some("expected table".to_string()),
+            })
+        }
+    }
+}
+
 impl<'lua, T: ToLua<'lua>> ToLua<'lua> for Option<T> {
     fn to_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
         match self {

src/error.rs

@@ -2,13 +2,14 @@ use std::error::Error as StdError;
 use std::fmt;
 use std::io::Error as IoError;
 use std::net::AddrParseError;
-use std::rc::Rc;
 use std::result::Result as StdResult;
 use std::str::Utf8Error;
 use std::string::String as StdString;
+use std::sync::Arc;
 
 /// Error type returned by `mlua` methods.
 #[derive(Debug, Clone)]
+#[non_exhaustive]
 pub enum Error {
     /// Syntax error while parsing Lua source code.
     SyntaxError {
@@ -36,6 +37,18 @@ pub enum Error {
     /// The Lua VM returns this error when there is an error running a `__gc` metamethod.
     #[cfg(any(feature = "lua53", feature = "lua52"))]
     GarbageCollectorError(StdString),
+    /// Potentially unsafe action in safe mode.
+    SafetyError(StdString),
+    /// Setting memory limit is not available.
+    ///
+    /// This error can only happen when Lua state was not created by us and does not have the
+    /// custom allocator attached.
+    MemoryLimitNotAvailable,
+    /// Main thread is not available.
+    ///
+    /// This error can only happen in Lua5.1/LuaJIT module mode, when module loaded within a coroutine.
+    /// These Lua versions does not have `LUA_RIDX_MAINTHREAD` registry key.
+    MainThreadNotAvailable,
     /// A mutable callback has triggered Lua code that has called the same mutable callback again.
     ///
     /// This is an error because a mutable callback can only be borrowed mutably once.
@@ -93,6 +106,13 @@ pub enum Error {
     /// [`AnyUserData`]: struct.AnyUserData.html
     /// [`UserDataMethods`]: trait.UserDataMethods.html
     UserDataTypeMismatch,
+    /// An [`AnyUserData`] borrow failed because it has been destructed.
+    ///
+    /// This error can happen either due to to being destructed in a previous __gc, or due to being
+    /// destructed from exiting a `Lua::scope` call.
+    ///
+    /// [`AnyUserData`]: struct.AnyUserData.html
+    UserDataDestructed,
     /// An [`AnyUserData`] immutable borrow failed because it is already borrowed mutably.
     ///
     /// This error can occur when a method on a [`UserData`] type calls back into Lua, which then
@@ -118,8 +138,21 @@ pub enum Error {
         /// Lua call stack backtrace.
         traceback: StdString,
         /// Original error returned by the Rust code.
-        cause: Rc<Error>,
+        cause: Arc<Error>,
     },
+    /// A Rust panic that was previosly resumed, returned again.
+    ///
+    /// This error can occur only when a Rust panic resumed previously was recovered
+    /// and returned again.
+    PreviouslyResumedPanic,
+    /// Serialization error.
+    #[cfg(feature = "serialize")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+    SerializeError(StdString),
+    /// Deserialization error.
+    #[cfg(feature = "serialize")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+    DeserializeError(StdString),
     /// A custom error.
     ///
     /// This can be used for returning user-defined errors from callbacks.
@@ -127,7 +160,10 @@ pub enum Error {
     /// Returning `Err(ExternalError(...))` from a Rust callback will raise the error as a Lua
     /// error. The Rust code that originally invoked the Lua code then receives a `CallbackError`,
     /// from which the original error (and a stack traceback) can be recovered.
-    ExternalError(Rc<dyn StdError>),
+    #[cfg(feature = "send")]
+    ExternalError(Arc<dyn StdError + Send + Sync>),
+    #[cfg(not(feature = "send"))]
+    ExternalError(Arc<dyn StdError>),
 }
 
 /// A specialized `Result` type used by `mlua`'s API.
@@ -145,6 +181,15 @@ impl fmt::Display for Error {
             Error::GarbageCollectorError(ref msg) => {
                 write!(fmt, "garbage collector error: {}", msg)
             }
+            Error::SafetyError(ref msg) => {
+                write!(fmt, "safety error: {}", msg)
+            },
+            Error::MemoryLimitNotAvailable => {
+                write!(fmt, "setting memory limit is not available")
+            }
+            Error::MainThreadNotAvailable => {
+                write!(fmt, "main thread is not available in Lua 5.1")
+            }
             Error::RecursiveMutCallback => write!(fmt, "mutable callback called recursively"),
             Error::CallbackDestructed => write!(
                 fmt,
@@ -182,6 +227,7 @@ impl fmt::Display for Error {
             }
             Error::CoroutineInactive => write!(fmt, "cannot resume inactive coroutine"),
             Error::UserDataTypeMismatch => write!(fmt, "userdata is not expected type"),
+            Error::UserDataDestructed => write!(fmt, "userdata has been destructed"),
             Error::UserDataBorrowError => write!(fmt, "userdata already mutably borrowed"),
             Error::UserDataBorrowMutError => write!(fmt, "userdata already borrowed"),
             Error::MismatchedRegistryKey => {
@@ -190,6 +236,17 @@ impl fmt::Display for Error {
             Error::CallbackError { ref traceback, .. } => {
                 write!(fmt, "callback error: {}", traceback)
             }
+            Error::PreviouslyResumedPanic => {
+                write!(fmt, "previously resumed panic returned again")
+            }
+            #[cfg(feature = "serialize")]
+            Error::SerializeError(ref err) => {
+                write!(fmt, "serialize error: {}", err)
+            },
+            #[cfg(feature = "serialize")]
+            Error::DeserializeError(ref err) => {
+                write!(fmt, "deserialize error: {}", err)
+            },
             Error::ExternalError(ref err) => write!(fmt, "{}", err),
         }
     }
@@ -206,6 +263,12 @@ impl StdError for Error {
 }
 
 impl Error {
+    #[cfg(feature = "send")]
+    pub fn external<T: Into<Box<dyn StdError + Send + Sync>>>(err: T) -> Error {
+        Error::ExternalError(err.into().into())
+    }
+
+    #[cfg(not(feature = "send"))]
     pub fn external<T: Into<Box<dyn StdError>>>(err: T) -> Error {
         Error::ExternalError(err.into().into())
     }
@@ -215,10 +278,15 @@ pub trait ExternalError {
     fn to_lua_err(self) -> Error;
 }
 
-impl<E> ExternalError for E
-where
-    E: Into<Box<dyn StdError>>,
-{
+#[cfg(feature = "send")]
+impl<E: Into<Box<dyn StdError + Send + Sync>>> ExternalError for E {
+    fn to_lua_err(self) -> Error {
+        Error::external(self)
+    }
+}
+
+#[cfg(not(feature = "send"))]
+impl<E: Into<Box<dyn StdError>>> ExternalError for E {
     fn to_lua_err(self) -> Error {
         Error::external(self)
     }
@@ -254,3 +322,17 @@ impl std::convert::From<Utf8Error> for Error {
         Error::external(err)
     }
 }
+
+#[cfg(feature = "serialize")]
+impl serde::ser::Error for Error {
+    fn custom<T: fmt::Display>(msg: T) -> Self {
+        Self::SerializeError(msg.to_string())
+    }
+}
+
+#[cfg(feature = "serialize")]
+impl serde::de::Error for Error {
+    fn custom<T: fmt::Display>(msg: T) -> Self {
+        Self::DeserializeError(msg.to_string())
+    }
+}

src/ffi/compat53.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019 A. Orlenko
+// Copyright (c) 2019-2021 A. Orlenko
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@@ -22,6 +22,8 @@
 
 // Based on github.com/keplerproject/lua-compat-5.3
 
+#![allow(clippy::needless_return)]
+
 use std::ffi::CStr;
 use std::mem;
 use std::os::raw::{c_char, c_int, c_void};
@@ -42,18 +44,18 @@ use super::lua::{
     lua_createtable, lua_dump_old, lua_error, lua_getfield_old, lua_getstack, lua_gettable_old,
     lua_gettop, lua_insert, lua_isstring, lua_istable, lua_newuserdata, lua_pop, lua_pushboolean,
     lua_pushcfunction, lua_pushfstring, lua_pushinteger, lua_pushliteral, lua_pushlstring_old,
-    lua_pushnumber, lua_pushthread, lua_pushvalue, lua_rawget_old, lua_rawgeti_old, lua_rawset,
-    lua_replace, lua_setfield, lua_setglobal, lua_setmetatable, lua_settable, lua_toboolean,
-    lua_tointeger, lua_tolstring, lua_tonumber, lua_topointer, lua_tostring, lua_touserdata,
-    lua_type, lua_typename,
+    lua_pushnil, lua_pushnumber, lua_pushthread, lua_pushvalue, lua_rawget_old, lua_rawgeti_old,
+    lua_rawset, lua_replace, lua_setfield, lua_setglobal, lua_setmetatable, lua_settable,
+    lua_toboolean, lua_tointeger, lua_tolstring, lua_tonumber, lua_topointer, lua_tostring,
+    lua_touserdata, lua_type, lua_typename,
 };
 
 #[cfg(any(feature = "lua51", feature = "luajit"))]
 use super::lua::{
     lua_checkstack, lua_concat, lua_equal, lua_getfenv, lua_getinfo, lua_getmetatable,
     lua_isnumber, lua_lessthan, lua_newtable, lua_next, lua_objlen, lua_pushcclosure,
-    lua_pushlightuserdata, lua_pushnil, lua_pushstring_old, lua_rawequal, lua_remove,
-    lua_resume_old, lua_setfenv, lua_settop, LUA_OPADD, LUA_OPUNM,
+    lua_pushlightuserdata, lua_pushstring_old, lua_rawequal, lua_remove, lua_resume_old,
+    lua_setfenv, lua_settop, LUA_OPADD, LUA_OPUNM,
 };
 
 #[cfg(feature = "lua52")]
@@ -114,7 +116,7 @@ unsafe fn compat53_checkmode(
         }
     }
 
-    if mode != ptr::null() && strchr(mode, *modename) == ptr::null() {
+    if !mode.is_null() && strchr(mode, *modename).is_null() {
         lua_pushfstring(
             L,
             cstr!("attempt to load a %s chunk (mode is '%s')"),
@@ -234,7 +236,7 @@ pub unsafe fn lua_absindex(L: *mut lua_State, mut idx: c_int) -> c_int {
 }
 
 #[cfg(any(feature = "lua51", feature = "luajit"))]
-static COMPAT53_ARITH_CODE: &'static str = r#"
+static COMPAT53_ARITH_CODE: &str = r#"
 local op,a,b=...
 if op == 0 then return a+b
 elseif op == 1 then return a-b
@@ -287,7 +289,7 @@ pub unsafe fn lua_isinteger(L: *mut lua_State, idx: c_int) -> c_int {
     if lua_type(L, idx) == lua::LUA_TNUMBER {
         let n = lua_tonumber(L, idx);
         let i = lua_tointeger(L, idx);
-        if i as f64 == n {
+        if (n - i as lua_Number).abs() < lua_Number::EPSILON {
             return 1;
         }
     }
@@ -297,7 +299,7 @@ pub unsafe fn lua_isinteger(L: *mut lua_State, idx: c_int) -> c_int {
 #[cfg(any(feature = "lua51", feature = "luajit"))]
 pub unsafe fn lua_tonumberx(L: *mut lua_State, i: c_int, isnum: *mut c_int) -> lua_Number {
     let n = lua_tonumber(L, i);
-    if isnum != ptr::null_mut() {
+    if !isnum.is_null() {
         *isnum = if n != 0.0 || lua_isnumber(L, i) != 0 {
             1
         } else {
@@ -312,15 +314,14 @@ pub unsafe fn lua_tonumberx(L: *mut lua_State, i: c_int, isnum: *mut c_int) -> l
 pub unsafe fn lua_tointegerx(L: *mut lua_State, i: c_int, isnum: *mut c_int) -> lua_Integer {
     let mut ok = 0;
     let n = lua_tonumberx(L, i, &mut ok);
-    if ok != 0 {
-        if n == n as lua_Integer as lua_Number {
-            if isnum != ptr::null_mut() {
-                *isnum = 1;
-            }
-            return n as lua_Integer;
+    let n_int = n as lua_Integer;
+    if ok != 0 && (n - n_int as lua_Number).abs() < lua_Number::EPSILON {
+        if !isnum.is_null() {
+            *isnum = 1;
         }
+        return n_int;
     }
-    if isnum != ptr::null_mut() {
+    if !isnum.is_null() {
         *isnum = 0;
     }
     return 0;
@@ -531,7 +532,7 @@ pub unsafe fn lua_getextraspace(L: *mut lua_State) -> *mut c_void {
     let is_main = lua_pushthread(L);
     lua_rawget(L, -2);
     let mut _ptr = lua_touserdata(L, -1);
-    if _ptr == ptr::null_mut() {
+    if _ptr.is_null() {
         lua_pop(L, 1);
         _ptr = lua_newuserdata(L, LUA_EXTRASPACE as usize);
         if is_main != 0 {
@@ -547,7 +548,7 @@ pub unsafe fn lua_getextraspace(L: *mut lua_State) -> *mut c_void {
             lua_pushboolean(L, 1);
             lua_rawget(L, -3);
             let mptr = lua_touserdata(L, -1);
-            if mptr != ptr::null_mut() {
+            if !mptr.is_null() {
                 ptr::copy_nonoverlapping(mptr, _ptr, LUA_EXTRASPACE as usize)
             } else {
                 ptr::write_bytes(_ptr, 0, LUA_EXTRASPACE as usize);
@@ -575,7 +576,7 @@ pub unsafe fn lua_pushglobaltable(L: *mut lua_State) {
 #[cfg(any(feature = "lua51", feature = "luajit"))]
 pub unsafe fn luaL_checkstack(L: *mut lua_State, sz: c_int, msg: *const c_char) {
     if lua_checkstack(L, sz + lua::LUA_MINSTACK) == 0 {
-        if msg != ptr::null() {
+        if !msg.is_null() {
             luaL_error(L, cstr!("stack overflow (%s)"), msg);
         } else {
             lua_pushliteral(L, "stack overflow");
@@ -654,7 +655,7 @@ pub unsafe fn luaL_traceback(
         0
     };
 
-    if msg != ptr::null() {
+    if !msg.is_null() {
         lua_pushfstring(L, cstr!("%s\n"), msg);
     }
     lua_pushliteral(L, "stack traceback:");
@@ -708,10 +709,8 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
                 }
             }
         };
-    } else {
-        if lua_isstring(L, -1) == 0 {
-            luaL_error(L, cstr!("'__tostring' must return a string"));
-        }
+    } else if lua_isstring(L, -1) == 0 {
+        luaL_error(L, cstr!("'__tostring' must return a string"));
     }
     lua_tolstring(L, -1, len)
 }
@@ -727,7 +726,7 @@ pub unsafe fn luaL_setmetatable(L: *mut lua_State, tname: *const c_char) {
 pub unsafe fn luaL_testudata(L: *mut lua_State, i: c_int, tname: *const c_char) -> *mut c_void {
     let mut p = lua_touserdata(L, i);
     luaL_checkstack(L, 2, cstr!("not enough stack slots"));
-    if p == ptr::null_mut() || lua_getmetatable(L, i) == 0 {
+    if p.is_null() || lua_getmetatable(L, i) == 0 {
         return ptr::null_mut();
     } else {
         luaL_getmetatable(L, tname);
@@ -743,7 +742,7 @@ pub unsafe fn luaL_testudata(L: *mut lua_State, i: c_int, tname: *const c_char)
 #[cfg(any(feature = "lua51", feature = "luajit"))]
 pub unsafe fn luaL_setfuncs(L: *mut lua_State, mut l: *const luaL_Reg, nup: c_int) {
     luaL_checkstack(L, nup + 1, cstr!("too many upvalues"));
-    while (*l).name != ptr::null() {
+    while !(*l).name.is_null() {
         // fill the table with given functions
         l = l.offset(1);
         lua_pushstring(L, (*l).name);
@@ -786,13 +785,25 @@ pub unsafe fn luaL_requiref(
         lua_pop(L, 1);
         lua_pushcfunction(L, openf);
         lua_pushstring(L, modname);
-        lua_call(L, 1, 1);
-        lua_pushvalue(L, -1);
-        lua_setfield(L, -3, modname);
+        #[cfg(any(feature = "lua52", feature = "lua51"))]
+        {
+            lua_call(L, 1, 1);
+            lua_pushvalue(L, -1);
+            lua_setfield(L, -3, modname);
+        }
+        #[cfg(feature = "luajit")]
+        {
+            lua_call(L, 1, 0);
+            lua_getfield(L, -1, modname);
+        }
     }
-    if glb != 0 {
+    if cfg!(any(feature = "lua52", feature = "lua51")) && glb != 0 {
         lua_pushvalue(L, -1);
         lua_setglobal(L, modname);
     }
+    if cfg!(feature = "luajit") && glb == 0 {
+        lua_pushnil(L);
+        lua_setglobal(L, modname);
+    }
     lua_replace(L, -2);
 }

src/ffi/glue/glue.c

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019 A. Orlenko
+// Copyright (c) 2019-2021 A. Orlenko
 // Copyright (c) 2014 J.C. Moyer
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -53,7 +53,7 @@ typedef struct rs_item {
 #define RS_INT(name, val)                                                      \
   { TY_INT, name, .int_val = val }
 
-#if LUA_VERSION_NUM == 503
+#if LUA_VERSION_NUM >= 503
 #define TY_LUAINT 1
 #define RS_LUAINT(name, val)                                                   \
   { TY_LUAINT, name, .lua_int_val = val }
@@ -84,6 +84,8 @@ const char *rs_int_type(int width) {
     return "i32";
   case 8:
     return "i64";
+  case 16:
+    return "i128";
   }
 }
 
@@ -96,6 +98,8 @@ const char *rs_uint_type(int width) {
     return "u32";
   case 8:
     return "u64";
+  case 16:
+    return "u128";
   }
 }
 
@@ -139,7 +143,7 @@ int write_int_item(FILE *f, const char *name, int value) {
   return fprintf(f, "pub const %s: c_int = %d;\n", name, value);
 }
 
-#if LUA_VERSION_NUM == 503
+#if LUA_VERSION_NUM >= 503
 int write_lua_int_item(FILE *f, const char *name, LUA_INTEGER value) {
   return fprintf(f, "pub const %s: LUA_INTEGER = " LUA_INTEGER_FMT ";\n", name,
                  value);
@@ -152,7 +156,7 @@ int write_str_item(FILE *f, const char *name, const char *value) {
   char *buf = malloc(bufsz);
   int ret;
   escape(value, buf, bufsz);
-  ret = fprintf(f, "pub const %s: &'static str = \"%s\";\n", name, buf);
+  ret = fprintf(f, "pub const %s: &str = \"%s\";\n", name, buf);
   free(buf);
   return ret;
 }
@@ -171,7 +175,7 @@ int write_item(FILE *f, const rs_item *c) {
   switch (c->type) {
   case TY_INT:
     return write_int_item(f, c->name, c->int_val);
-#if LUA_VERSION_NUM == 503
+#if LUA_VERSION_NUM >= 503
   case TY_LUAINT:
     return write_lua_int_item(f, c->name, c->lua_int_val);
 #endif
@@ -221,12 +225,8 @@ int main(int argc, const char **argv) {
       // == luaconf.h ==========================================================
 
       RS_COMMENT("luaconf.h"),
-      RS_STR("LUA_PATH_DEFAULT", LUA_PATH_DEFAULT),
-      RS_STR("LUA_CPATH_DEFAULT", LUA_CPATH_DEFAULT),
-      RS_STR("LUA_DIRSEP", LUA_DIRSEP),
       RS_INT("LUA_EXTRASPACE", LUA_EXTRASPACE),
       RS_INT("LUA_IDSIZE", LUA_IDSIZE),
-      RS_INT("LUAL_BUFFERSIZE", LUAL_BUFFERSIZE),
       RS_TYPE("LUA_NUMBER",
               sizeof(LUA_NUMBER) > sizeof(float) ? "c_double" : "c_float"),
       RS_TYPE("LUA_INTEGER", rs_int_type(sizeof(LUA_INTEGER))),
@@ -240,8 +240,6 @@ int main(int argc, const char **argv) {
 
       RS_COMMENT("lua.h"),
       RS_INT("LUA_VERSION_NUM", LUA_VERSION_NUM),
-      RS_STR("LUA_VERSION", LUA_VERSION),
-      RS_STR("LUA_RELEASE", LUA_RELEASE),
       RS_INT("LUA_REGISTRYINDEX", LUA_REGISTRYINDEX),
 #if LUA_VERSION_NUM == 501
       RS_INT("LUA_ENVIRONINDEX", LUA_ENVIRONINDEX),
@@ -251,7 +249,7 @@ int main(int argc, const char **argv) {
       // == lauxlib.h ==========================================================
 
       RS_COMMENT("lauxlib.h"),
-#if LUA_VERSION_NUM == 503
+#if LUA_VERSION_NUM >= 503
       RS_INT("LUAL_NUMSIZES", LUAL_NUMSIZES),
 #endif
 

src/ffi/lauxlib.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019 A. Orlenko
+// Copyright (c) 2019-2021 A. Orlenko
 // Copyright (c) 2014 J.C. Moyer
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -28,7 +28,7 @@ use std::ptr;
 
 use super::lua::{self, lua_CFunction, lua_Integer, lua_Number, lua_State};
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use super::glue::LUAL_NUMSIZES;
 
 #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
@@ -49,10 +49,10 @@ pub struct luaL_Reg {
     pub func: lua_CFunction,
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn luaL_checkversion(L: *mut lua_State) {
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     luaL_checkversion_(
         L,
         lua::LUA_VERSION_NUM as lua_Number,
@@ -63,19 +63,19 @@ pub unsafe fn luaL_checkversion(L: *mut lua_State) {
 }
 
 extern "C" {
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn luaL_checkversion_(L: *mut lua_State, ver: lua_Number, sz: usize);
     #[cfg(feature = "lua52")]
     pub fn luaL_checkversion_(L: *mut lua_State, ver: lua_Number);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn luaL_getmetafield(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     #[link_name = "luaL_getmetafield"]
     pub fn luaL_getmetafield_old(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
 
     pub fn luaL_callmeta(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char;
     pub fn luaL_argerror(L: *mut lua_State, arg: c_int, l: *const c_char) -> c_int;
     pub fn luaL_checklstring(L: *mut lua_State, arg: c_int, l: *mut usize) -> *const c_char;
@@ -90,20 +90,20 @@ extern "C" {
     pub fn luaL_checkinteger(L: *mut lua_State, arg: c_int) -> lua_Integer;
     pub fn luaL_optinteger(L: *mut lua_State, arg: c_int, def: lua_Integer) -> lua_Integer;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_checkstack(L: *mut lua_State, sz: c_int, msg: *const c_char);
     pub fn luaL_checktype(L: *mut lua_State, arg: c_int, t: c_int);
     pub fn luaL_checkany(L: *mut lua_State, arg: c_int);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn luaL_newmetatable(L: *mut lua_State, tname: *const c_char) -> c_int;
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     #[link_name = "luaL_newmetatable"]
     pub fn luaL_newmetatable_old(L: *mut lua_State, tname: *const c_char) -> c_int;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_setmetatable(L: *mut lua_State, tname: *const c_char);
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_testudata(L: *mut lua_State, ud: c_int, tname: *const c_char) -> *mut c_void;
     pub fn luaL_checkudata(L: *mut lua_State, ud: c_int, tname: *const c_char) -> *mut c_void;
 
@@ -118,9 +118,9 @@ extern "C" {
         lst: *const *const c_char,
     ) -> c_int;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_fileresult(L: *mut lua_State, stat: c_int, fname: *const c_char) -> c_int;
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_execresult(L: *mut lua_State, stat: c_int) -> c_int;
 }
 
@@ -132,21 +132,21 @@ extern "C" {
     pub fn luaL_ref(L: *mut lua_State, t: c_int) -> c_int;
     pub fn luaL_unref(L: *mut lua_State, t: c_int, r: c_int);
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_loadfilex(L: *mut lua_State, filename: *const c_char, mode: *const c_char)
         -> c_int;
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     pub fn luaL_loadfile(L: *mut lua_State, filename: *const c_char) -> c_int;
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn luaL_loadfile(L: *mut lua_State, f: *const c_char) -> c_int {
     luaL_loadfilex(L, f, ptr::null())
 }
 
 extern "C" {
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_loadbufferx(
         L: *mut lua_State,
         buff: *const c_char,
@@ -165,9 +165,11 @@ extern "C" {
 
     pub fn luaL_newstate() -> *mut lua_State;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_len(L: *mut lua_State, idx: c_int) -> lua_Integer;
 
+    // TODO (lua54): luaL_addgsub
+
     pub fn luaL_gsub(
         L: *mut lua_State,
         s: *const c_char,
@@ -175,17 +177,17 @@ extern "C" {
         r: *const c_char,
     ) -> *const c_char;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_setfuncs(L: *mut lua_State, l: *const luaL_Reg, nup: c_int);
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_getsubtable(L: *mut lua_State, idx: c_int, fname: *const c_char) -> c_int;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaL_traceback(L: *mut lua_State, L1: *mut lua_State, msg: *const c_char, level: c_int);
 
     // Skip Lua 5.2 implementation in favor of the compat53 one
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn luaL_requiref(
         L: *mut lua_State,
         modname: *const c_char,
@@ -288,7 +290,7 @@ pub unsafe fn luaL_getmetatable(L: *mut lua_State, n: *const c_char) {
 
 // luaL_opt would be implemented here but it is undocumented, so it's omitted
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn luaL_loadbuffer(
     L: *mut lua_State,
@@ -301,4 +303,4 @@ pub unsafe fn luaL_loadbuffer(
 
 // TODO: Add buffer API
 
-// omitted: old module system compatibility
+// omitted: old module system compatibility (removed in 5.4)

src/ffi/lua.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019 A. Orlenko
+// Copyright (c) 2019-2021 A. Orlenko
 // Copyright (c) 2014 J.C. Moyer
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -23,20 +23,23 @@
 
 //! Contains definitions from `lua.h`.
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 use std::os::raw::c_uchar;
 use std::os::raw::{c_char, c_int, c_void};
+#[cfg(feature = "lua54")]
+use std::os::raw::{c_uint, c_ushort};
 use std::ptr;
 
 use super::luaconf;
 
-pub use super::glue::{LUA_RELEASE, LUA_VERSION, LUA_VERSION_NUM};
-
-pub use super::glue::LUA_REGISTRYINDEX;
 #[cfg(any(feature = "lua51", feature = "luajit"))]
 pub use super::glue::{LUA_ENVIRONINDEX, LUA_GLOBALSINDEX};
+pub use super::glue::{LUA_REGISTRYINDEX, LUA_VERSION_NUM};
 
-pub const LUA_SIGNATURE: &'static [u8] = b"\x1bLua";
+#[cfg(not(feature = "luajit"))]
+pub const LUA_SIGNATURE: &[u8] = b"\x1bLua";
+#[cfg(feature = "luajit")]
+pub const LUA_SIGNATURE: &[u8] = b"\x1bLJ";
 
 // option for multiple returns in 'lua_pcall' and 'lua_call'
 pub const LUA_MULTRET: c_int = -1;
@@ -51,13 +54,14 @@ pub use super::compat53::{
 #[cfg(any(feature = "lua51", feature = "luajit"))]
 pub use super::compat53::{
     lua_absindex, lua_arith, lua_compare, lua_copy, lua_len, lua_pushglobaltable, lua_pushstring,
-    lua_rawlen, lua_rawsetp, lua_resume, lua_setuservalue, lua_tonumberx, lua_upvalueindex,
+    lua_rawlen, lua_rawsetp, lua_resume as lua_resume_53, lua_setuservalue, lua_tonumberx,
+    lua_upvalueindex,
 };
 
 #[cfg(feature = "lua52")]
 pub use super::compat53::lua_getglobal;
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub fn lua_upvalueindex(i: c_int) -> c_int {
     LUA_REGISTRYINDEX - i
@@ -71,7 +75,7 @@ pub const LUA_ERRSYNTAX: c_int = 3;
 pub const LUA_ERRMEM: c_int = 4;
 #[cfg(any(feature = "lua53", feature = "lua52"))]
 pub const LUA_ERRGCMM: c_int = 5;
-#[cfg(any(feature = "lua51", feature = "luajit"))]
+#[cfg(any(feature = "lua54", feature = "lua51", feature = "luajit"))]
 pub const LUA_ERRERR: c_int = 5;
 #[cfg(any(feature = "lua53", feature = "lua52"))]
 pub const LUA_ERRERR: c_int = 6;
@@ -91,6 +95,8 @@ pub const LUA_TFUNCTION: c_int = 6;
 pub const LUA_TUSERDATA: c_int = 7;
 pub const LUA_TTHREAD: c_int = 8;
 
+#[cfg(feature = "lua54")]
+pub const LUA_NUMTYPES: c_int = 9;
 #[cfg(any(feature = "lua53", feature = "lua52"))]
 pub const LUA_NUMTAGS: c_int = 9;
 
@@ -98,11 +104,11 @@ pub const LUA_NUMTAGS: c_int = 9;
 pub const LUA_MINSTACK: c_int = 20;
 
 // predefined values in the registry
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 pub const LUA_RIDX_MAINTHREAD: lua_Integer = 1;
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 pub const LUA_RIDX_GLOBALS: lua_Integer = 2;
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 pub const LUA_RIDX_LAST: lua_Integer = LUA_RIDX_GLOBALS;
 
 /// A Lua number, usually equivalent to `f64`.
@@ -115,14 +121,14 @@ pub type lua_Integer = luaconf::LUA_INTEGER;
 pub type lua_Unsigned = luaconf::LUA_UNSIGNED;
 
 // type for continuation-function contexts
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub type lua_KContext = luaconf::LUA_KCONTEXT;
 
 /// Type for native functions that can be passed to Lua.
 pub type lua_CFunction = unsafe extern "C" fn(L: *mut lua_State) -> c_int;
 
 // Type for continuation functions
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub type lua_KFunction =
     unsafe extern "C" fn(L: *mut lua_State, status: c_int, ctx: lua_KContext) -> c_int;
 
@@ -132,7 +138,7 @@ pub type lua_Reader =
 pub type lua_Writer =
     unsafe extern "C" fn(L: *mut lua_State, p: *const c_void, sz: usize, ud: *mut c_void) -> c_int;
 
-/// Type for memory-allocation functions.
+// Type for memory-allocation functions.
 pub type lua_Alloc = unsafe extern "C" fn(
     ud: *mut c_void,
     ptr: *mut c_void,
@@ -140,19 +146,28 @@ pub type lua_Alloc = unsafe extern "C" fn(
     nsize: usize,
 ) -> *mut c_void;
 
+// Type for warning functions
+#[cfg(feature = "lua54")]
+pub type lua_WarnFunction =
+    unsafe extern "C" fn(ud: *mut c_void, msg: *const c_char, tocont: c_int);
+
 extern "C" {
     // state manipulation
     pub fn lua_newstate(f: lua_Alloc, ud: *mut c_void) -> *mut lua_State;
     pub fn lua_close(L: *mut lua_State);
     pub fn lua_newthread(L: *mut lua_State) -> *mut lua_State;
+    #[cfg(feature = "lua54")]
+    pub fn lua_resetthread(L: *mut lua_State) -> c_int;
 
     pub fn lua_atpanic(L: *mut lua_State, panicf: lua_CFunction) -> lua_CFunction;
 
+    #[cfg(feature = "lua54")]
+    pub fn lua_version(L: *mut lua_State) -> lua_Number;
     #[cfg(feature = "lua53")]
     pub fn lua_version(L: *mut lua_State) -> *const lua_Number;
 
     // basic stack manipulation
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_absindex(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_gettop(L: *mut lua_State) -> c_int;
     pub fn lua_settop(L: *mut lua_State, idx: c_int);
@@ -163,9 +178,9 @@ extern "C" {
     pub fn lua_insert(L: *mut lua_State, idx: c_int);
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     pub fn lua_replace(L: *mut lua_State, idx: c_int);
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_rotate(L: *mut lua_State, idx: c_int, n: c_int);
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_copy(L: *mut lua_State, fromidx: c_int, toidx: c_int);
     pub fn lua_checkstack(L: *mut lua_State, sz: c_int) -> c_int;
 
@@ -175,7 +190,7 @@ extern "C" {
     pub fn lua_isnumber(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_isstring(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_iscfunction(L: *mut lua_State, idx: c_int) -> c_int;
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_isinteger(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_isuserdata(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_type(L: *mut lua_State, idx: c_int) -> c_int;
@@ -183,17 +198,17 @@ extern "C" {
 
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     pub fn lua_tonumber(L: *mut lua_State, idx: c_int) -> lua_Number;
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_tonumberx(L: *mut lua_State, idx: c_int, isnum: *mut c_int) -> lua_Number;
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     pub fn lua_tointeger(L: *mut lua_State, idx: c_int) -> lua_Integer;
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_tointegerx(L: *mut lua_State, idx: c_int, isnum: *mut c_int) -> lua_Integer;
     pub fn lua_toboolean(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char;
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     pub fn lua_objlen(L: *mut lua_State, idx: c_int) -> usize;
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_rawlen(L: *mut lua_State, idx: c_int) -> usize;
     pub fn lua_tocfunction(L: *mut lua_State, idx: c_int) -> lua_CFunction;
     pub fn lua_touserdata(L: *mut lua_State, idx: c_int) -> *mut c_void;
@@ -215,31 +230,31 @@ pub const LUA_OPPOW: c_int = 5;
 #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
 pub const LUA_OPUNM: c_int = 6;
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPMOD: c_int = 3;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPPOW: c_int = 4;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPDIV: c_int = 5;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPIDIV: c_int = 6;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPBAND: c_int = 7;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPBOR: c_int = 8;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPBXOR: c_int = 9;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPSHL: c_int = 10;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPSHR: c_int = 11;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPUNM: c_int = 12;
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub const LUA_OPBNOT: c_int = 13;
 
 extern "C" {
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_arith(L: *mut lua_State, op: c_int);
 }
 
@@ -253,7 +268,7 @@ extern "C" {
     pub fn lua_rawequal(L: *mut lua_State, idx1: c_int, idx2: c_int) -> c_int;
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     pub fn lua_lessthan(L: *mut lua_State, idx1: c_int, idx2: c_int) -> c_int;
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_compare(L: *mut lua_State, idx1: c_int, idx2: c_int, op: c_int) -> c_int;
 }
 
@@ -263,13 +278,13 @@ extern "C" {
     pub fn lua_pushnumber(L: *mut lua_State, n: lua_Number);
     pub fn lua_pushinteger(L: *mut lua_State, n: lua_Integer);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_pushlstring(L: *mut lua_State, s: *const c_char, l: usize) -> *const c_char;
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     #[link_name = "lua_pushlstring"]
     pub fn lua_pushlstring_old(L: *mut lua_State, s: *const c_char, l: usize) -> *const c_char;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_pushstring(L: *mut lua_State, s: *const c_char) -> *const c_char;
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     #[link_name = "lua_pushstring"]
@@ -286,49 +301,59 @@ extern "C" {
 
 // get functions (Lua -> stack)
 extern "C" {
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_getglobal(L: *mut lua_State, var: *const c_char) -> c_int;
     #[cfg(feature = "lua52")]
     #[link_name = "lua_getglobal"]
     pub fn lua_getglobal_old(L: *mut lua_State, var: *const c_char);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_gettable(L: *mut lua_State, idx: c_int) -> c_int;
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     #[link_name = "lua_gettable"]
     pub fn lua_gettable_old(L: *mut lua_State, idx: c_int);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_getfield(L: *mut lua_State, idx: c_int, k: *const c_char) -> c_int;
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     #[link_name = "lua_getfield"]
     pub fn lua_getfield_old(L: *mut lua_State, idx: c_int, k: *const c_char);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_geti(L: *mut lua_State, idx: c_int, n: lua_Integer) -> c_int;
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_rawget(L: *mut lua_State, idx: c_int) -> c_int;
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     #[link_name = "lua_rawget"]
     pub fn lua_rawget_old(L: *mut lua_State, idx: c_int);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_rawgeti(L: *mut lua_State, idx: c_int, n: lua_Integer) -> c_int;
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     #[link_name = "lua_rawgeti"]
     pub fn lua_rawgeti_old(L: *mut lua_State, idx: c_int, n: lua_Integer);
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_rawgetp(L: *mut lua_State, idx: c_int, p: *const c_void) -> c_int;
     #[cfg(feature = "lua52")]
     #[link_name = "lua_rawgetp"]
     pub fn lua_rawgetp_old(L: *mut lua_State, idx: c_int, p: *const c_void);
 
     pub fn lua_createtable(L: *mut lua_State, narr: c_int, nrec: c_int);
+    #[cfg(feature = "lua54")]
+    pub fn lua_newuserdatauv(L: *mut lua_State, sz: usize, nuvalue: c_int) -> *mut c_void;
+    #[cfg(any(
+        feature = "lua53",
+        feature = "lua52",
+        feature = "lua51",
+        feature = "luajit"
+    ))]
     pub fn lua_newuserdata(L: *mut lua_State, sz: usize) -> *mut c_void;
     pub fn lua_getmetatable(L: *mut lua_State, objindex: c_int) -> c_int;
 
+    #[cfg(feature = "lua54")]
+    pub fn lua_getiuservalue(L: *mut lua_State, idx: c_int, n: c_int) -> c_int;
     #[cfg(feature = "lua53")]
     pub fn lua_getuservalue(L: *mut lua_State, idx: c_int) -> c_int;
     #[cfg(feature = "lua52")]
@@ -338,28 +363,48 @@ extern "C" {
     pub fn lua_getfenv(L: *mut lua_State, idx: c_int);
 }
 
+#[cfg(feature = "lua54")]
+#[inline(always)]
+pub unsafe fn lua_newuserdata(L: *mut lua_State, sz: usize) -> *mut c_void {
+    lua_newuserdatauv(L, sz, 1)
+}
+
+#[cfg(feature = "lua54")]
+#[inline(always)]
+pub unsafe fn lua_getuservalue(L: *mut lua_State, idx: c_int) -> c_int {
+    lua_getiuservalue(L, idx, 1)
+}
+
 // set functions (stack -> Lua)
 extern "C" {
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_setglobal(L: *mut lua_State, var: *const c_char);
     pub fn lua_settable(L: *mut lua_State, idx: c_int);
     pub fn lua_setfield(L: *mut lua_State, idx: c_int, k: *const c_char);
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_seti(L: *mut lua_State, idx: c_int, n: lua_Integer);
     pub fn lua_rawset(L: *mut lua_State, idx: c_int);
     pub fn lua_rawseti(L: *mut lua_State, idx: c_int, n: lua_Integer);
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_rawsetp(L: *mut lua_State, idx: c_int, p: *const c_void);
     pub fn lua_setmetatable(L: *mut lua_State, objindex: c_int) -> c_int;
+    #[cfg(feature = "lua54")]
+    pub fn lua_setiuservalue(L: *mut lua_State, idx: c_int, n: c_int) -> c_int;
     #[cfg(any(feature = "lua53", feature = "lua52"))]
     pub fn lua_setuservalue(L: *mut lua_State, idx: c_int);
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     pub fn lua_setfenv(L: *mut lua_State, idx: c_int) -> c_int;
 }
 
+#[cfg(feature = "lua54")]
+#[inline(always)]
+pub unsafe fn lua_setuservalue(L: *mut lua_State, idx: c_int) {
+    lua_setiuservalue(L, idx, 1);
+}
+
 // 'load' and 'call' functions (load and run Lua code)
 extern "C" {
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_callk(
         L: *mut lua_State,
         nargs: c_int,
@@ -376,7 +421,7 @@ extern "C" {
         k: Option<lua_CFunction>,
     );
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_pcallk(
         L: *mut lua_State,
         nargs: c_int,
@@ -412,7 +457,7 @@ extern "C" {
         mode: *const c_char,
     ) -> c_int;
 
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_dump(
         L: *mut lua_State,
         writer: lua_Writer,
@@ -424,13 +469,13 @@ extern "C" {
     pub fn lua_dump_old(L: *mut lua_State, writer: lua_Writer, data: *mut c_void) -> c_int;
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn lua_call(L: *mut lua_State, n: c_int, r: c_int) {
     lua_callk(L, n, r, 0, None)
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn lua_pcall(L: *mut lua_State, n: c_int, r: c_int, f: c_int) -> c_int {
     lua_pcallk(L, n, r, f, 0, None)
@@ -438,7 +483,7 @@ pub unsafe fn lua_pcall(L: *mut lua_State, n: c_int, r: c_int, f: c_int) -> c_in
 
 // coroutine functions
 extern "C" {
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_yieldk(
         L: *mut lua_State,
         nresults: c_int,
@@ -455,23 +500,57 @@ extern "C" {
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     pub fn lua_yield(L: *mut lua_State, nresults: c_int) -> c_int;
 
+    #[cfg(feature = "lua54")]
+    pub fn lua_resume(
+        L: *mut lua_State,
+        from: *mut lua_State,
+        narg: c_int,
+        nres: *mut c_int,
+    ) -> c_int;
     #[cfg(any(feature = "lua53", feature = "lua52"))]
-    pub fn lua_resume(L: *mut lua_State, from: *mut lua_State, narg: c_int) -> c_int;
+    #[link_name = "lua_resume"]
+    pub fn lua_resume_53(L: *mut lua_State, from: *mut lua_State, narg: c_int) -> c_int;
     #[cfg(any(feature = "lua51", feature = "luajit"))]
     #[link_name = "lua_resume"]
     pub fn lua_resume_old(L: *mut lua_State, narg: c_int) -> c_int;
 
     pub fn lua_status(L: *mut lua_State) -> c_int;
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_isyieldable(L: *mut lua_State) -> c_int;
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn lua_yield(L: *mut lua_State, n: c_int) -> c_int {
     lua_yieldk(L, n, 0, None)
 }
 
+#[cfg(any(
+    feature = "lua53",
+    feature = "lua52",
+    feature = "lua51",
+    feature = "luajit"
+))]
+pub unsafe fn lua_resume(
+    L: *mut lua_State,
+    from: *mut lua_State,
+    narg: c_int,
+    nres: *mut c_int,
+) -> c_int {
+    let ret = lua_resume_53(L, from, narg);
+    if ret == LUA_OK || ret == LUA_YIELD {
+        *nres = lua_gettop(L);
+    }
+    ret
+}
+
+// warning-related functions
+#[cfg(feature = "lua54")]
+extern "C" {
+    pub fn lua_setwarnf(L: *mut lua_State, f: lua_WarnFunction, ud: *mut c_void);
+    pub fn lua_warning(L: *mut lua_State, msg: *const c_char, tocont: c_int);
+}
+
 // garbage-collection function and options
 pub const LUA_GCSTOP: c_int = 0;
 pub const LUA_GCRESTART: c_int = 1;
@@ -481,10 +560,22 @@ pub const LUA_GCCOUNTB: c_int = 4;
 pub const LUA_GCSTEP: c_int = 5;
 pub const LUA_GCSETPAUSE: c_int = 6;
 pub const LUA_GCSETSTEPMUL: c_int = 7;
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 pub const LUA_GCISRUNNING: c_int = 9;
+#[cfg(feature = "lua54")]
+pub const LUA_GCGEN: c_int = 10;
+#[cfg(feature = "lua54")]
+pub const LUA_GCINC: c_int = 11;
 
 extern "C" {
+    #[cfg(feature = "lua54")]
+    pub fn lua_gc(L: *mut lua_State, what: c_int, ...) -> c_int;
+    #[cfg(any(
+        feature = "lua53",
+        feature = "lua52",
+        feature = "lua51",
+        feature = "luajit"
+    ))]
     pub fn lua_gc(L: *mut lua_State, what: c_int, data: c_int) -> c_int;
 }
 
@@ -493,29 +584,31 @@ extern "C" {
     pub fn lua_error(L: *mut lua_State) -> !;
     pub fn lua_next(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_concat(L: *mut lua_State, n: c_int);
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_len(L: *mut lua_State, idx: c_int);
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn lua_stringtonumber(L: *mut lua_State, s: *const c_char) -> usize;
     pub fn lua_getallocf(L: *mut lua_State, ud: *mut *mut c_void) -> lua_Alloc;
     pub fn lua_setallocf(L: *mut lua_State, f: lua_Alloc, ud: *mut c_void);
+    #[cfg(feature = "lua54")]
+    pub fn lua_toclose(L: *mut lua_State, idx: c_int);
 }
 
 // some useful macros
 // here, implemented as Rust functions
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 #[inline(always)]
 pub unsafe fn lua_getextraspace(L: *mut lua_State) -> *mut c_void {
     L.offset(-super::glue::LUA_EXTRASPACE as isize) as *mut c_void
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn lua_tonumber(L: *mut lua_State, i: c_int) -> lua_Number {
     lua_tonumberx(L, i, ptr::null_mut())
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn lua_tointeger(L: *mut lua_State, i: c_int) -> lua_Integer {
     lua_tointegerx(L, i, ptr::null_mut())
@@ -601,7 +694,7 @@ pub unsafe fn lua_getglobal(L: *mut lua_State, var: *const c_char) -> c_int {
     lua_getfield(L, LUA_GLOBALSINDEX, var)
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[inline(always)]
 pub unsafe fn lua_pushglobaltable(L: *mut lua_State) -> c_int {
     lua_rawgeti(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS)
@@ -612,20 +705,20 @@ pub unsafe fn lua_tostring(L: *mut lua_State, i: c_int) -> *const c_char {
     lua_tolstring(L, i, ptr::null_mut())
 }
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 #[inline(always)]
 pub unsafe fn lua_insert(L: *mut lua_State, idx: c_int) {
     lua_rotate(L, idx, 1)
 }
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 #[inline(always)]
 pub unsafe fn lua_remove(L: *mut lua_State, idx: c_int) {
     lua_rotate(L, idx, -1);
     lua_pop(L, 1)
 }
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 #[inline(always)]
 pub unsafe fn lua_replace(L: *mut lua_State, idx: c_int) {
     lua_copy(L, -1, idx);
@@ -647,7 +740,7 @@ pub const LUA_MASKLINE: c_int = 1 << (LUA_HOOKLINE as usize);
 pub const LUA_MASKCOUNT: c_int = 1 << (LUA_HOOKCOUNT as usize);
 
 /// Type for functions to be called on debug events.
-pub type lua_Hook = extern "C" fn(L: *mut lua_State, ar: *mut lua_Debug);
+pub type lua_Hook = unsafe extern "C" fn(L: *mut lua_State, ar: *mut lua_Debug);
 
 extern "C" {
     pub fn lua_getstack(L: *mut lua_State, level: c_int, ar: *mut lua_Debug) -> c_int;
@@ -657,18 +750,21 @@ extern "C" {
     pub fn lua_getupvalue(L: *mut lua_State, funcindex: c_int, n: c_int) -> *const c_char;
     pub fn lua_setupvalue(L: *mut lua_State, funcindex: c_int, n: c_int) -> *const c_char;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_upvalueid(L: *mut lua_State, fidx: c_int, n: c_int) -> *mut c_void;
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn lua_upvaluejoin(L: *mut lua_State, fidx1: c_int, n1: c_int, fidx2: c_int, n2: c_int);
 
-    pub fn lua_sethook(L: *mut lua_State, func: lua_Hook, mask: c_int, count: c_int);
+    pub fn lua_sethook(L: *mut lua_State, func: Option<lua_Hook>, mask: c_int, count: c_int);
     pub fn lua_gethook(L: *mut lua_State) -> Option<lua_Hook>;
     pub fn lua_gethookmask(L: *mut lua_State) -> c_int;
     pub fn lua_gethookcount(L: *mut lua_State) -> c_int;
+
+    #[cfg(feature = "lua54")]
+    pub fn lua_setcstacklimit(L: *mut lua_State, limit: c_uint) -> c_int;
 }
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 #[repr(C)]
 pub struct lua_Debug {
     pub event: c_int,
@@ -676,6 +772,8 @@ pub struct lua_Debug {
     pub namewhat: *const c_char,
     pub what: *const c_char,
     pub source: *const c_char,
+    #[cfg(feature = "lua54")]
+    pub srclen: usize,
     pub currentline: c_int,
     pub linedefined: c_int,
     pub lastlinedefined: c_int,
@@ -683,6 +781,10 @@ pub struct lua_Debug {
     pub nparams: c_uchar,
     pub isvararg: c_char,
     pub istailcall: c_char,
+    #[cfg(feature = "lua54")]
+    pub ftransfer: c_ushort,
+    #[cfg(feature = "lua54")]
+    pub ntransfer: c_ushort,
     pub short_src: [c_char; luaconf::LUA_IDSIZE as usize],
     // lua.h mentions this is for private use
     i_ci: *mut c_void,

src/ffi/luaconf.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019 A. Orlenko
+// Copyright (c) 2019-2021 A. Orlenko
 // Copyright (c) 2014 J.C. Moyer
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -23,15 +23,14 @@
 
 //! Contains definitions from `luaconf.h`.
 
-pub use super::glue::LUAL_BUFFERSIZE;
 pub use super::glue::LUA_INTEGER;
 pub use super::glue::LUA_NUMBER;
 pub use super::glue::LUA_UNSIGNED;
 
 pub use super::glue::LUA_IDSIZE;
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use super::glue::LUAL_NUMSIZES;
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub type LUA_KCONTEXT = isize; // intptr_t

src/ffi/lualib.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019 A. Orlenko
+// Copyright (c) 2019-2021 A. Orlenko
 // Copyright (c) 2014 J.C. Moyer
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -32,7 +32,7 @@ pub use super::glue::{
     LUA_STRLIBNAME, LUA_TABLIBNAME,
 };
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use super::glue::LUA_UTF8LIBNAME;
 
 #[cfg(any(feature = "lua52", feature = "luajit"))]
@@ -43,13 +43,13 @@ pub use super::glue::{LUA_FFILIBNAME, LUA_JITLIBNAME};
 
 extern "C" {
     pub fn luaopen_base(L: *mut lua_State) -> c_int;
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     pub fn luaopen_coroutine(L: *mut lua_State) -> c_int;
     pub fn luaopen_table(L: *mut lua_State) -> c_int;
     pub fn luaopen_io(L: *mut lua_State) -> c_int;
     pub fn luaopen_os(L: *mut lua_State) -> c_int;
     pub fn luaopen_string(L: *mut lua_State) -> c_int;
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     pub fn luaopen_utf8(L: *mut lua_State) -> c_int;
     #[cfg(feature = "lua52")]
     pub fn luaopen_bit32(L: *mut lua_State) -> c_int;

src/ffi/mod.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019 A. Orlenko
+// Copyright (c) 2019-2021 A. Orlenko
 // Copyright (c) 2014 J.C. Moyer
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -36,11 +36,14 @@ pub use self::lua::{
     lua_Unsigned, lua_Writer,
 };
 
-#[cfg(feature = "lua53")]
+#[cfg(feature = "lua54")]
+pub use self::lua::lua_WarnFunction;
+
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use self::lua::{lua_KContext, lua_KFunction};
 
 #[cfg(any(feature = "lua51", feature = "luajit"))]
-pub use self::lua::lua_setfenv;
+pub use self::lua::{lua_getfenv, lua_setfenv};
 
 // C API functions
 pub use self::lua::{
@@ -155,10 +158,16 @@ pub use self::lua::{
     lua_yield,
 };
 
-#[cfg(feature = "lua53")]
+#[cfg(feature = "lua54")]
+pub use self::lua::{
+    lua_getiuservalue, lua_newuserdatauv, lua_resetthread, lua_setcstacklimit, lua_setiuservalue,
+    lua_setwarnf, lua_toclose, lua_warning,
+};
+
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use self::lua::{lua_isyieldable, lua_version};
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 pub use self::lua::{lua_callk, lua_pcallk, lua_upvalueid, lua_upvaluejoin, lua_yieldk};
 
 // auxiliary library types
@@ -177,7 +186,7 @@ pub use self::lauxlib::{
     luaL_where,
 };
 
-#[cfg(any(feature = "lua53", feature = "lua52"))]
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 pub use self::lauxlib::{luaL_execresult, luaL_fileresult, luaL_loadfilex};
 
 // lualib.h functions
@@ -186,7 +195,7 @@ pub use self::lualib::{
     luaopen_package, luaopen_string, luaopen_table,
 };
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use self::lualib::{luaopen_coroutine, luaopen_utf8};
 
 #[cfg(feature = "lua52")]
@@ -202,17 +211,23 @@ pub use self::lua::{
     LUA_HOOKCOUNT, LUA_HOOKLINE, LUA_HOOKRET, LUA_HOOKTAILCALL, LUA_MASKCALL, LUA_MASKCOUNT,
     LUA_MASKLINE, LUA_MASKRET, LUA_MINSTACK, LUA_MULTRET, LUA_OK, LUA_OPADD, LUA_OPDIV, LUA_OPEQ,
     LUA_OPLE, LUA_OPLT, LUA_OPMOD, LUA_OPMUL, LUA_OPPOW, LUA_OPSUB, LUA_OPUNM, LUA_REGISTRYINDEX,
-    LUA_TBOOLEAN, LUA_TFUNCTION, LUA_TLIGHTUSERDATA, LUA_TNIL, LUA_TNONE, LUA_TNUMBER, LUA_TSTRING,
-    LUA_TTABLE, LUA_TTHREAD, LUA_TUSERDATA, LUA_YIELD,
+    LUA_SIGNATURE, LUA_TBOOLEAN, LUA_TFUNCTION, LUA_TLIGHTUSERDATA, LUA_TNIL, LUA_TNONE,
+    LUA_TNUMBER, LUA_TSTRING, LUA_TTABLE, LUA_TTHREAD, LUA_TUSERDATA, LUA_YIELD,
 };
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use self::lua::{
     LUA_OPBAND, LUA_OPBNOT, LUA_OPBOR, LUA_OPBXOR, LUA_OPIDIV, LUA_OPSHL, LUA_OPSHR,
 };
 
+#[cfg(feature = "lua54")]
+pub use self::lua::{LUA_GCGEN, LUA_GCINC};
+
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+pub use self::lua::{LUA_GCISRUNNING, LUA_RIDX_GLOBALS, LUA_RIDX_MAINTHREAD};
+
 #[cfg(any(feature = "lua53", feature = "lua52"))]
-pub use self::lua::{LUA_ERRGCMM, LUA_GCISRUNNING, LUA_RIDX_GLOBALS, LUA_RIDX_MAINTHREAD};
+pub use self::lua::LUA_ERRGCMM;
 
 #[cfg(any(feature = "lua51", feature = "luajit"))]
 pub use self::lua::{LUA_ENVIRONINDEX, LUA_GLOBALSINDEX};
@@ -226,7 +241,7 @@ pub use self::lualib::{
     LUA_STRLIBNAME, LUA_TABLIBNAME,
 };
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua54", feature = "lua53"))]
 pub use self::lualib::LUA_UTF8LIBNAME;
 
 #[cfg(any(feature = "lua52", feature = "luajit"))]
@@ -238,7 +253,30 @@ pub use self::lualib::{LUA_FFILIBNAME, LUA_JITLIBNAME};
 // Not actually defined in lua.h / luaconf.h
 pub const LUA_MAX_UPVALUES: c_int = 255;
 
+// Copied from https://github.com/rust-lang/rust/blob/master/src/libstd/sys_common/alloc.rs
+#[cfg(all(any(
+    target_arch = "x86",
+    target_arch = "arm",
+    target_arch = "mips",
+    target_arch = "powerpc",
+    target_arch = "powerpc64",
+    target_arch = "asmjs",
+    target_arch = "wasm32",
+    target_arch = "hexagon"
+)))]
+pub const SYS_MIN_ALIGN: usize = 8;
+#[cfg(all(any(
+    target_arch = "x86_64",
+    target_arch = "aarch64",
+    target_arch = "mips64",
+    target_arch = "s390x",
+    target_arch = "sparc64",
+    target_arch = "riscv64"
+)))]
+pub const SYS_MIN_ALIGN: usize = 16;
+
 #[allow(unused_imports, dead_code, non_camel_case_types)]
+#[allow(clippy::unreadable_literal)]
 mod glue {
     include!(concat!(env!("OUT_DIR"), "/glue.rs"));
 }

src/function.rs

@@ -1,5 +1,5 @@
-use std::os::raw::c_int;
-use std::ptr;
+use std::os::raw::{c_int, c_void};
+use std::{ptr, slice};
 
 use crate::error::{Error, Result};
 use crate::ffi;
@@ -94,6 +94,8 @@ impl<'lua> Function<'lua> {
     ///
     /// Internaly it wraps the function to an [`AsyncThread`].
     ///
+    /// Requires `feature = "async"`
+    ///
     /// # Examples
     ///
     /// ```
@@ -117,6 +119,7 @@ impl<'lua> Function<'lua> {
     ///
     /// [`AsyncThread`]: struct.AsyncThread.html
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub fn call_async<'fut, A, R>(&self, args: A) -> LocalBoxFuture<'fut, Result<R>>
     where
         'lua: 'fut,
@@ -203,6 +206,42 @@ impl<'lua> Function<'lua> {
             Ok(Function(lua.pop_ref()))
         }
     }
+
+    /// Dumps the function as a binary chunk.
+    ///
+    /// If `strip` is true, the binary representation may not include all debug information
+    /// about the function, to save space.
+    pub fn dump(&self, strip: bool) -> Result<Vec<u8>> {
+        unsafe extern "C" fn writer(
+            _state: *mut ffi::lua_State,
+            buf: *const c_void,
+            buf_len: usize,
+            data: *mut c_void,
+        ) -> c_int {
+            let data = &mut *(data as *mut Vec<u8>);
+            let buf = slice::from_raw_parts(buf as *const u8, buf_len);
+            data.extend_from_slice(buf);
+            0
+        }
+
+        let lua = self.0.lua;
+        let mut data: Vec<u8> = Vec::new();
+        unsafe {
+            let _sg = StackGuard::new(lua.state);
+            assert_stack(lua.state, 1);
+            lua.push_ref(&self.0);
+            let strip = if strip { 1 } else { 0 };
+            ffi::lua_dump(
+                lua.state,
+                writer,
+                &mut data as *mut Vec<u8> as *mut c_void,
+                strip,
+            );
+            ffi::lua_pop(lua.state, 1);
+        }
+
+        Ok(data)
+    }
 }
 
 impl<'lua> PartialEq for Function<'lua> {

src/hook.rs

@@ -0,0 +1,195 @@
+use std::ffi::CStr;
+use std::marker::PhantomData;
+use std::os::raw::{c_char, c_int};
+
+use crate::ffi::{self, lua_Debug, lua_State};
+use crate::lua::Lua;
+use crate::util::callback_error;
+
+/// Contains information about currently executing Lua code.
+///
+/// The `Debug` structure is provided as a parameter to the hook function set with
+/// [`Lua::set_hook`].  You may call the methods on this structure to retrieve information about the
+/// Lua code executing at the time that the hook function was called.  Further information can be
+/// found in the [Lua 5.3 documentaton][lua_doc].
+///
+/// [lua_doc]: https://www.lua.org/manual/5.3/manual.html#lua_Debug
+/// [`Lua::set_hook`]: struct.Lua.html#method.set_hook
+#[derive(Clone)]
+pub struct Debug<'a> {
+    ar: *mut lua_Debug,
+    state: *mut lua_State,
+    _phantom: PhantomData<&'a ()>,
+}
+
+impl<'a> Debug<'a> {
+    /// Corresponds to the `n` what mask.
+    pub fn names(&self) -> DebugNames<'a> {
+        unsafe {
+            mlua_assert!(
+                ffi::lua_getinfo(self.state, cstr!("n"), self.ar) != 0,
+                "lua_getinfo failed with `n`"
+            );
+            DebugNames {
+                name: ptr_to_str((*self.ar).name),
+                name_what: ptr_to_str((*self.ar).namewhat),
+            }
+        }
+    }
+
+    /// Corresponds to the `S` what mask.
+    pub fn source(&self) -> DebugSource<'a> {
+        unsafe {
+            mlua_assert!(
+                ffi::lua_getinfo(self.state, cstr!("S"), self.ar) != 0,
+                "lua_getinfo failed with `S`"
+            );
+            DebugSource {
+                source: ptr_to_str((*self.ar).source),
+                short_src: ptr_to_str((*self.ar).short_src.as_ptr()),
+                line_defined: (*self.ar).linedefined as i32,
+                last_line_defined: (*self.ar).lastlinedefined as i32,
+                what: ptr_to_str((*self.ar).what),
+            }
+        }
+    }
+
+    /// Corresponds to the `l` what mask. Returns the current line.
+    pub fn curr_line(&self) -> i32 {
+        unsafe {
+            mlua_assert!(
+                ffi::lua_getinfo(self.state, cstr!("l"), self.ar) != 0,
+                "lua_getinfo failed with `l`"
+            );
+            (*self.ar).currentline as i32
+        }
+    }
+
+    /// Corresponds to the `t` what mask. Returns true if the hook is in a function tail call, false
+    /// otherwise.
+    pub fn is_tail_call(&self) -> bool {
+        unsafe {
+            mlua_assert!(
+                ffi::lua_getinfo(self.state, cstr!("t"), self.ar) != 0,
+                "lua_getinfo failed with `t`"
+            );
+            (*self.ar).currentline != 0
+        }
+    }
+
+    /// Corresponds to the `u` what mask.
+    pub fn stack(&self) -> DebugStack {
+        unsafe {
+            mlua_assert!(
+                ffi::lua_getinfo(self.state, cstr!("u"), self.ar) != 0,
+                "lua_getinfo failed with `u`"
+            );
+            DebugStack {
+                num_ups: (*self.ar).nups as i32,
+                #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+                num_params: (*self.ar).nparams as i32,
+                #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+                is_vararg: (*self.ar).isvararg != 0,
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct DebugNames<'a> {
+    pub name: Option<&'a [u8]>,
+    pub name_what: Option<&'a [u8]>,
+}
+
+#[derive(Clone, Debug)]
+pub struct DebugSource<'a> {
+    pub source: Option<&'a [u8]>,
+    pub short_src: Option<&'a [u8]>,
+    pub line_defined: i32,
+    pub last_line_defined: i32,
+    pub what: Option<&'a [u8]>,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct DebugStack {
+    pub num_ups: i32,
+    /// Requires `feature = "lua54/lua53/lua52"`
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", doc))]
+    pub num_params: i32,
+    /// Requires `feature = "lua54/lua53/lua52"`
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", doc))]
+    pub is_vararg: bool,
+}
+
+/// Determines when a hook function will be called by Lua.
+#[derive(Clone, Copy, Debug, Default)]
+pub struct HookTriggers {
+    /// Before a function call.
+    pub on_calls: bool,
+    /// When Lua returns from a function.
+    pub on_returns: bool,
+    /// Before executing a new line, or returning from a function call.
+    pub every_line: bool,
+    /// After a certain number of VM instructions have been executed.  When set to `Some(count)`,
+    /// `count` is the number of VM instructions to execute before calling the hook.
+    ///
+    /// # Performance
+    ///
+    /// Setting this option to a low value can incur a very high overhead.
+    pub every_nth_instruction: Option<u32>,
+}
+
+impl HookTriggers {
+    // Compute the mask to pass to `lua_sethook`.
+    pub(crate) fn mask(&self) -> c_int {
+        let mut mask: c_int = 0;
+        if self.on_calls {
+            mask |= ffi::LUA_MASKCALL
+        }
+        if self.on_returns {
+            mask |= ffi::LUA_MASKRET
+        }
+        if self.every_line {
+            mask |= ffi::LUA_MASKLINE
+        }
+        if self.every_nth_instruction.is_some() {
+            mask |= ffi::LUA_MASKCOUNT
+        }
+        mask
+    }
+
+    // Returns the `count` parameter to pass to `lua_sethook`, if applicable. Otherwise, zero is
+    // returned.
+    pub(crate) fn count(&self) -> c_int {
+        self.every_nth_instruction.unwrap_or(0) as c_int
+    }
+}
+
+pub(crate) unsafe extern "C" fn hook_proc(state: *mut lua_State, ar: *mut lua_Debug) {
+    callback_error(state, |_| {
+        let debug = Debug {
+            ar,
+            state,
+            _phantom: PhantomData,
+        };
+
+        let lua = Lua::make_from_ptr(state);
+        let hook_cb = mlua_expect!(lua.hook_callback(), "no hook callback set in hook_proc");
+
+        #[allow(clippy::match_wild_err_arm)]
+        match hook_cb.try_borrow_mut() {
+            Ok(mut b) => (&mut *b)(&lua, debug),
+            Err(_) => mlua_panic!("Lua should not allow hooks to be called within another hook"),
+        }?;
+
+        Ok(())
+    });
+}
+
+unsafe fn ptr_to_str<'a>(input: *const c_char) -> Option<&'a [u8]> {
+    if input.is_null() {
+        None
+    } else {
+        Some(CStr::from_ptr(input).to_bytes())
+    }
+}

src/lib.rs

@@ -24,12 +24,30 @@
 //! The [`UserData`] trait can be implemented by user-defined types to make them available to Lua.
 //! Methods and operators to be used from Lua can be added using the [`UserDataMethods`] API.
 //!
+//! # Serde support
+//!
+//! The [`LuaSerdeExt`] trait implemented for [`Lua`] allows conversion from Rust types to Lua values
+//! and vice versa using serde. Any user defined data type that implements [`serde::Serialize`] or
+//! [`serde::Deserialize`] can be converted.
+//! For convenience, additional functionality to handle `NULL` values and arrays is provided.
+//!
+//! The [`Value`] enum implements [`serde::Serialize`] trait to support serializing Lua values
+//! (including [`UserData`]) into Rust values.
+//!
+//! Requires `feature = "serialize"`.
+//!
 //! # Async/await support
 //!
 //! The [`create_async_function`] allows creating non-blocking functions that returns [`Future`].
 //! Lua code with async capabilities can be executed by [`call_async`] family of functions or polling
 //! [`AsyncThread`] using any runtime (eg. Tokio).
 //!
+//! Requires `feature = "async"`.
+//!
+//! # `Send` requirement
+//! By default `mlua` is `!Send`. This can be changed by enabling `feature = "send"` that adds `Send` requirement
+//! to [`Function`]s and [`UserData`].
+//!
 //! [Lua programming language]: https://www.lua.org/
 //! [`Lua`]: struct.Lua.html
 //! [executing]: struct.Lua.html#method.exec
@@ -39,16 +57,24 @@
 //! [`FromLua`]: trait.FromLua.html
 //! [`ToLuaMulti`]: trait.ToLuaMulti.html
 //! [`FromLuaMulti`]: trait.FromLuaMulti.html
+//! [`Function`]: struct.Function.html
 //! [`UserData`]: trait.UserData.html
 //! [`UserDataMethods`]: trait.UserDataMethods.html
+//! [`LuaSerdeExt`]: serde/trait.LuaSerdeExt.html
+//! [`Value`]: enum.Value.html
 //! [`create_async_function`]: struct.Lua.html#method.create_async_function
 //! [`call_async`]: struct.Function.html#method.call_async
 //! [`AsyncThread`]: struct.AsyncThread.html
 //! [`Future`]: ../futures_core/future/trait.Future.html
+//! [`serde::Serialize`]: https://docs.serde.rs/serde/ser/trait.Serialize.html
+//! [`serde::Deserialize`]: https://docs.serde.rs/serde/de/trait.Deserialize.html
 
+// mlua types in rustdoc of other crates get linked to here.
+#![doc(html_root_url = "https://docs.rs/mlua/0.5.4")]
 // Deny warnings inside doc tests / examples. When this isn't present, rustdoc doesn't show *any*
 // warnings at all.
 #![doc(test(attr(deny(warnings))))]
+#![cfg_attr(docsrs, feature(doc_cfg))]
 
 #[macro_use]
 mod macros;
@@ -57,8 +83,10 @@ mod conversion;
 mod error;
 mod ffi;
 mod function;
+mod hook;
 mod lua;
 mod multi;
+mod scope;
 mod stdlib;
 mod string;
 mod table;
@@ -72,8 +100,10 @@ pub use crate::ffi::lua_State;
 
 pub use crate::error::{Error, ExternalError, ExternalResult, Result};
 pub use crate::function::Function;
-pub use crate::lua::{Chunk, Lua};
+pub use crate::hook::{Debug, DebugNames, DebugSource, DebugStack, HookTriggers};
+pub use crate::lua::{Chunk, ChunkMode, GCMode, Lua};
 pub use crate::multi::Variadic;
+pub use crate::scope::Scope;
 pub use crate::stdlib::StdLib;
 pub use crate::string::String;
 pub use crate::table::{Table, TableExt, TablePairs, TableSequence};
@@ -85,4 +115,19 @@ pub use crate::value::{FromLua, FromLuaMulti, MultiValue, Nil, ToLua, ToLuaMulti
 #[cfg(feature = "async")]
 pub use crate::thread::AsyncThread;
 
+#[cfg(feature = "serialize")]
+pub use crate::serde::LuaSerdeExt;
+
 pub mod prelude;
+#[cfg(feature = "serialize")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+pub mod serde;
+
+// Re-export #[mlua_derive::lua_module].
+#[cfg(feature = "mlua_derive")]
+#[allow(unused_imports)]
+#[macro_use]
+extern crate mlua_derive;
+#[cfg(feature = "mlua_derive")]
+#[doc(hidden)]
+pub use mlua_derive::*;

src/macros.rs

@@ -78,3 +78,19 @@ macro_rules! mlua_expect {
         mlua_expect!($res, $msg)
     };
 }
+
+#[cfg(feature = "module")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! require_module_feature {
+    () => {};
+}
+
+#[cfg(not(feature = "module"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! require_module_feature {
+    () => {
+        compile_error!("Feature `module` must be enabled in the `mlua` crate");
+    };
+}

src/multi.rs

@@ -34,7 +34,7 @@ impl<'lua, T: ToLua<'lua>> ToLuaMulti<'lua> for T {
 
 impl<'lua, T: FromLua<'lua>> FromLuaMulti<'lua> for T {
     fn from_lua_multi(mut values: MultiValue<'lua>, lua: &'lua Lua) -> Result<Self> {
-        Ok(T::from_lua(values.pop_front().unwrap_or(Nil), lua)?)
+        T::from_lua(values.pop_front().unwrap_or(Nil), lua)
     }
 }
 

src/prelude.rs

@@ -3,12 +3,13 @@
 pub use crate::{
     AnyUserData as LuaAnyUserData, Chunk as LuaChunk, Error as LuaError,
     ExternalError as LuaExternalError, ExternalResult as LuaExternalResult, FromLua, FromLuaMulti,
-    Function as LuaFunction, Integer as LuaInteger, LightUserData as LuaLightUserData, Lua,
-    MetaMethod as LuaMetaMethod, MultiValue as LuaMultiValue, Nil as LuaNil, Number as LuaNumber,
-    RegistryKey as LuaRegistryKey, Result as LuaResult, String as LuaString, Table as LuaTable,
-    TableExt as LuaTableExt, TablePairs as LuaTablePairs, TableSequence as LuaTableSequence,
-    Thread as LuaThread, ThreadStatus as LuaThreadStatus, ToLua, ToLuaMulti,
-    UserData as LuaUserData, UserDataMethods as LuaUserDataMethods, Value as LuaValue,
+    Function as LuaFunction, GCMode as LuaGCMode, Integer as LuaInteger,
+    LightUserData as LuaLightUserData, Lua, MetaMethod as LuaMetaMethod,
+    MultiValue as LuaMultiValue, Nil as LuaNil, Number as LuaNumber, RegistryKey as LuaRegistryKey,
+    Result as LuaResult, String as LuaString, Table as LuaTable, TableExt as LuaTableExt,
+    TablePairs as LuaTablePairs, TableSequence as LuaTableSequence, Thread as LuaThread,
+    ThreadStatus as LuaThreadStatus, ToLua, ToLuaMulti, UserData as LuaUserData,
+    UserDataMethods as LuaUserDataMethods, Value as LuaValue,
 };
 
 #[cfg(feature = "async")]

src/scope.rs

@@ -0,0 +1,662 @@
+use std::any::Any;
+use std::cell::{Cell, Ref, RefCell, RefMut};
+use std::marker::PhantomData;
+use std::mem;
+use std::os::raw::c_void;
+use std::rc::Rc;
+
+#[cfg(feature = "serialize")]
+use serde::Serialize;
+
+use crate::error::{Error, Result};
+use crate::ffi;
+use crate::function::Function;
+use crate::lua::Lua;
+use crate::types::{Callback, LuaRef, MaybeSend, UserDataCell};
+use crate::userdata::{AnyUserData, MetaMethod, UserData, UserDataMethods, UserDataWrapped};
+use crate::util::{
+    assert_stack, init_userdata_metatable, protect_lua_closure, push_string, push_userdata,
+    take_userdata, StackGuard,
+};
+use crate::value::{FromLuaMulti, MultiValue, ToLuaMulti, Value};
+
+#[cfg(feature = "async")]
+use {
+    crate::types::AsyncCallback,
+    futures_core::future::{Future, LocalBoxFuture},
+    futures_util::future::{self, TryFutureExt},
+};
+
+/// Constructed by the [`Lua::scope`] method, allows temporarily creating Lua userdata and
+/// callbacks that are not required to be Send or 'static.
+///
+/// See [`Lua::scope`] for more details.
+///
+/// [`Lua::scope`]: struct.Lua.html#method.scope
+#[allow(clippy::type_complexity)]
+pub struct Scope<'lua, 'scope> {
+    lua: &'lua Lua,
+    destructors: RefCell<Vec<(LuaRef<'lua>, fn(LuaRef<'lua>) -> Vec<Box<dyn Any>>)>>,
+    _scope_invariant: PhantomData<Cell<&'scope ()>>,
+}
+
+impl<'lua, 'scope> Scope<'lua, 'scope> {
+    pub(crate) fn new(lua: &'lua Lua) -> Scope<'lua, 'scope> {
+        Scope {
+            lua,
+            destructors: RefCell::new(Vec::new()),
+            _scope_invariant: PhantomData,
+        }
+    }
+
+    /// Wraps a Rust function or closure, creating a callable Lua function handle to it.
+    ///
+    /// This is a version of [`Lua::create_function`] that creates a callback which expires on
+    /// scope drop.  See [`Lua::scope`] for more details.
+    ///
+    /// [`Lua::create_function`]: struct.Lua.html#method.create_function
+    /// [`Lua::scope`]: struct.Lua.html#method.scope
+    pub fn create_function<'callback, A, R, F>(&'callback self, func: F) -> Result<Function<'lua>>
+    where
+        A: FromLuaMulti<'callback>,
+        R: ToLuaMulti<'callback>,
+        F: 'scope + Fn(&'callback Lua, A) -> Result<R>,
+    {
+        // Safe, because 'scope must outlive 'callback (due to Self containing 'scope), however the
+        // callback itself must be 'scope lifetime, so the function should not be able to capture
+        // anything of 'callback lifetime.  'scope can't be shortened due to being invariant, and
+        // the 'callback lifetime here can't be enlarged due to coming from a universal
+        // quantification in Lua::scope.
+        //
+        // I hope I got this explanation right, but in any case this is tested with compiletest_rs
+        // to make sure callbacks can't capture handles with lifetime outside the scope, inside the
+        // scope, and owned inside the callback itself.
+        unsafe {
+            self.create_callback(Box::new(move |lua, args| {
+                func(lua, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            }))
+        }
+    }
+
+    /// Wraps a Rust mutable closure, creating a callable Lua function handle to it.
+    ///
+    /// This is a version of [`Lua::create_function_mut`] that creates a callback which expires
+    /// on scope drop.  See [`Lua::scope`] and [`Scope::create_function`] for more details.
+    ///
+    /// [`Lua::create_function_mut`]: struct.Lua.html#method.create_function_mut
+    /// [`Lua::scope`]: struct.Lua.html#method.scope
+    /// [`Scope::create_function`]: #method.create_function
+    pub fn create_function_mut<'callback, A, R, F>(
+        &'callback self,
+        func: F,
+    ) -> Result<Function<'lua>>
+    where
+        A: FromLuaMulti<'callback>,
+        R: ToLuaMulti<'callback>,
+        F: 'scope + FnMut(&'callback Lua, A) -> Result<R>,
+    {
+        let func = RefCell::new(func);
+        self.create_function(move |lua, args| {
+            (&mut *func
+                .try_borrow_mut()
+                .map_err(|_| Error::RecursiveMutCallback)?)(lua, args)
+        })
+    }
+
+    /// Wraps a Rust async function or closure, creating a callable Lua function handle to it.
+    ///
+    /// This is a version of [`Lua::create_async_function`] that creates a callback which expires on
+    /// scope drop.  See [`Lua::scope`] and [`Lua::async_scope`] for more details.
+    ///
+    /// Requires `feature = "async"`
+    ///
+    /// [`Lua::create_async_function`]: struct.Lua.html#method.create_async_function
+    /// [`Lua::scope`]: struct.Lua.html#method.scope
+    /// [`Lua::async_scope`]: struct.Lua.html#method.async_scope
+    #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+    pub fn create_async_function<'callback, A, R, F, FR>(
+        &'callback self,
+        func: F,
+    ) -> Result<Function<'lua>>
+    where
+        A: FromLuaMulti<'callback>,
+        R: ToLuaMulti<'callback>,
+        F: 'scope + Fn(&'callback Lua, A) -> FR,
+        FR: 'callback + Future<Output = Result<R>>,
+    {
+        unsafe {
+            self.create_async_callback(Box::new(move |lua, args| {
+                let args = match A::from_lua_multi(args, lua) {
+                    Ok(args) => args,
+                    Err(e) => return Box::pin(future::err(e)),
+                };
+                Box::pin(func(lua, args).and_then(move |ret| future::ready(ret.to_lua_multi(lua))))
+            }))
+        }
+    }
+
+    /// Create a Lua userdata object from a custom userdata type.
+    ///
+    /// This is a version of [`Lua::create_userdata`] that creates a userdata which expires on
+    /// scope drop, and does not require that the userdata type be Send (but still requires that the
+    /// UserData be 'static).
+    /// See [`Lua::scope`] for more details.
+    ///
+    /// [`Lua::create_userdata`]: struct.Lua.html#method.create_userdata
+    /// [`Lua::scope`]: struct.Lua.html#method.scope
+    pub fn create_userdata<T>(&self, data: T) -> Result<AnyUserData<'lua>>
+    where
+        T: 'static + UserData,
+    {
+        self.create_userdata_inner(UserDataWrapped::new(data))
+    }
+
+    /// Create a Lua userdata object from a custom serializable userdata type.
+    ///
+    /// This is a version of [`Lua::create_ser_userdata`] that creates a userdata which expires on
+    /// scope drop, and does not require that the userdata type be Send (but still requires that the
+    /// UserData be 'static).
+    /// See [`Lua::scope`] for more details.
+    ///
+    /// Requires `feature = "serialize"`
+    ///
+    /// [`Lua::create_ser_userdata`]: struct.Lua.html#method.create_ser_userdata
+    /// [`Lua::scope`]: struct.Lua.html#method.scope
+    #[cfg(feature = "serialize")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+    pub fn create_ser_userdata<T>(&self, data: T) -> Result<AnyUserData<'lua>>
+    where
+        T: 'static + UserData + Serialize,
+    {
+        self.create_userdata_inner(UserDataWrapped::new_ser(data))
+    }
+
+    fn create_userdata_inner<T>(&self, data: UserDataWrapped<T>) -> Result<AnyUserData<'lua>>
+    where
+        T: 'static + UserData,
+    {
+        // Safe even though T may not be Send, because the parent Lua cannot be sent to another
+        // thread while the Scope is alive (or the returned AnyUserData handle even).
+        unsafe {
+            let u = self.lua.make_userdata(data)?;
+            self.destructors.borrow_mut().push((u.0.clone(), |u| {
+                let state = u.lua.state;
+                assert_stack(state, 2);
+                u.lua.push_ref(&u);
+                // We know the destructor has not run yet because we hold a reference to the
+                // userdata.
+                vec![Box::new(take_userdata::<UserDataCell<T>>(state))]
+            }));
+            Ok(u)
+        }
+    }
+
+    /// Create a Lua userdata object from a custom userdata type.
+    ///
+    /// This is a version of [`Lua::create_userdata`] that creates a userdata which expires on
+    /// scope drop, and does not require that the userdata type be Send or 'static. See
+    /// [`Lua::scope`] for more details.
+    ///
+    /// Lifting the requirement that the UserData type be 'static comes with some important
+    /// limitations, so if you only need to eliminate the Send requirement, it is probably better to
+    /// use [`Scope::create_userdata`] instead.
+    ///
+    /// The main limitation that comes from using non-'static userdata is that the produced userdata
+    /// will no longer have a `TypeId` associated with it, becuase `TypeId` can only work for
+    /// 'static types.  This means that it is impossible, once the userdata is created, to get a
+    /// reference to it back *out* of an `AnyUserData` handle.  This also implies that the
+    /// "function" type methods that can be added via [`UserDataMethods`] (the ones that accept
+    /// `AnyUserData` as a first parameter) are vastly less useful.  Also, there is no way to re-use
+    /// a single metatable for multiple non-'static types, so there is a higher cost associated with
+    /// creating the userdata metatable each time a new userdata is created.
+    ///
+    /// [`Scope::create_userdata`]: #method.create_userdata
+    /// [`Lua::create_userdata`]: struct.Lua.html#method.create_userdata
+    /// [`Lua::scope`]: struct.Lua.html#method.scope
+    /// [`UserDataMethods`]: trait.UserDataMethods.html
+    pub fn create_nonstatic_userdata<T>(&self, data: T) -> Result<AnyUserData<'lua>>
+    where
+        T: 'scope + UserData,
+    {
+        let data = Rc::new(RefCell::new(UserDataWrapped::new(data)));
+
+        // 'callback outliving 'scope is a lie to make the types work out, required due to the
+        // inability to work with the more correct callback type that is universally quantified over
+        // 'lua.  This is safe though, because `UserData::add_methods` does not get to pick the 'lua
+        // lifetime, so none of the static methods UserData types can add can possibly capture
+        // parameters.
+        fn wrap_method<'scope, 'lua, 'callback: 'scope, T: 'scope>(
+            scope: &Scope<'lua, 'scope>,
+            data: Rc<UserDataCell<T>>,
+            method: NonStaticMethod<'callback, T>,
+        ) -> Result<Function<'lua>> {
+            // On methods that actually receive the userdata, we fake a type check on the passed in
+            // userdata, where we pretend there is a unique type per call to
+            // `Scope::create_nonstatic_userdata`.  You can grab a method from a userdata and call
+            // it on a mismatched userdata type, which when using normal 'static userdata will fail
+            // with a type mismatch, but here without this check would proceed as though you had
+            // called the method on the original value (since we otherwise completely ignore the
+            // first argument).
+            let check_data = data.clone();
+            let check_ud_type = move |lua: &'callback Lua, value| {
+                if let Some(Value::UserData(ud)) = value {
+                    unsafe {
+                        assert_stack(lua.state, 1);
+                        lua.push_ref(&ud.0);
+                        ffi::lua_getuservalue(lua.state, -1);
+                        #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
+                        {
+                            ffi::lua_rawgeti(lua.state, -1, 1);
+                            ffi::lua_remove(lua.state, -2);
+                        }
+                        return ffi::lua_touserdata(lua.state, -1)
+                            == check_data.as_ptr() as *mut c_void;
+                    }
+                }
+
+                false
+            };
+
+            match method {
+                NonStaticMethod::Method(method) => {
+                    let f = Box::new(move |lua, mut args: MultiValue<'callback>| {
+                        if !check_ud_type(lua, args.pop_front()) {
+                            return Err(Error::UserDataTypeMismatch);
+                        }
+                        let data = data
+                            .try_borrow()
+                            .map(|cell| Ref::map(cell, AsRef::as_ref))
+                            .map_err(|_| Error::UserDataBorrowError)?;
+                        method(lua, &*data, args)
+                    });
+                    unsafe { scope.create_callback(f) }
+                }
+                NonStaticMethod::MethodMut(method) => {
+                    let method = RefCell::new(method);
+                    let f = Box::new(move |lua, mut args: MultiValue<'callback>| {
+                        if !check_ud_type(lua, args.pop_front()) {
+                            return Err(Error::UserDataTypeMismatch);
+                        }
+                        let mut method = method
+                            .try_borrow_mut()
+                            .map_err(|_| Error::RecursiveMutCallback)?;
+                        let mut data = data
+                            .try_borrow_mut()
+                            .map(|cell| RefMut::map(cell, AsMut::as_mut))
+                            .map_err(|_| Error::UserDataBorrowMutError)?;
+                        (&mut *method)(lua, &mut *data, args)
+                    });
+                    unsafe { scope.create_callback(f) }
+                }
+                NonStaticMethod::Function(function) => unsafe { scope.create_callback(function) },
+                NonStaticMethod::FunctionMut(function) => {
+                    let function = RefCell::new(function);
+                    let f = Box::new(move |lua, args| {
+                        (&mut *function
+                            .try_borrow_mut()
+                            .map_err(|_| Error::RecursiveMutCallback)?)(
+                            lua, args
+                        )
+                    });
+                    unsafe { scope.create_callback(f) }
+                }
+            }
+        }
+
+        let mut ud_methods = NonStaticUserDataMethods::default();
+        T::add_methods(&mut ud_methods);
+
+        unsafe {
+            let lua = self.lua;
+            let _sg = StackGuard::new(lua.state);
+            assert_stack(lua.state, 6);
+
+            // We need to wrap dummy userdata because their memory can be accessed by serializer
+            push_userdata(lua.state, UserDataCell::new(UserDataWrapped::new(())))?;
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
+            ffi::lua_pushlightuserdata(lua.state, data.as_ptr() as *mut c_void);
+            #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
+            protect_lua_closure(lua.state, 0, 1, |state| {
+                // Lua 5.2/5.1 allows to store only table. Then we will wrap the value.
+                ffi::lua_createtable(state, 1, 0);
+                ffi::lua_pushlightuserdata(state, data.as_ptr() as *mut c_void);
+                ffi::lua_rawseti(state, -2, 1);
+            })?;
+            ffi::lua_setuservalue(lua.state, -2);
+
+            protect_lua_closure(lua.state, 0, 1, move |state| {
+                ffi::lua_newtable(state);
+            })?;
+
+            for (k, m) in ud_methods.meta_methods {
+                push_string(lua.state, k.name())?;
+                lua.push_value(Value::Function(wrap_method(self, data.clone(), m)?))?;
+
+                protect_lua_closure(lua.state, 3, 1, |state| {
+                    ffi::lua_rawset(state, -3);
+                })?;
+            }
+
+            if ud_methods.methods.is_empty() {
+                init_userdata_metatable::<()>(lua.state, -1, None)?;
+            } else {
+                protect_lua_closure(lua.state, 0, 1, |state| {
+                    ffi::lua_newtable(state);
+                })?;
+                for (k, m) in ud_methods.methods {
+                    push_string(lua.state, &k)?;
+                    lua.push_value(Value::Function(wrap_method(self, data.clone(), m)?))?;
+                    protect_lua_closure(lua.state, 3, 1, |state| {
+                        ffi::lua_rawset(state, -3);
+                    })?;
+                }
+
+                init_userdata_metatable::<()>(lua.state, -2, Some(-1))?;
+                ffi::lua_pop(lua.state, 1);
+            }
+
+            let mt_id = ffi::lua_topointer(lua.state, -1);
+            ffi::lua_setmetatable(lua.state, -2);
+
+            let ud = AnyUserData(lua.pop_ref());
+            lua.register_userdata_metatable(mt_id as isize);
+            self.destructors.borrow_mut().push((ud.0.clone(), |ud| {
+                let state = ud.lua.state;
+                assert_stack(state, 2);
+                ud.lua.push_ref(&ud);
+                ffi::lua_getmetatable(state, -1);
+                let mt_id = ffi::lua_topointer(state, -1);
+                ffi::lua_pop(state, 1);
+                ud.lua.deregister_userdata_metatable(mt_id as isize);
+                vec![Box::new(take_userdata::<UserDataCell<()>>(state))]
+            }));
+            Ok(ud)
+        }
+    }
+
+    // Unsafe, because the callback can improperly capture any value with 'callback scope, such as
+    // improperly capturing an argument. Since the 'callback lifetime is chosen by the user and the
+    // lifetime of the callback itself is 'scope (non-'static), the borrow checker will happily pick
+    // a 'callback that outlives 'scope to allow this.  In order for this to be safe, the callback
+    // must NOT capture any parameters.
+    unsafe fn create_callback<'callback>(
+        &self,
+        f: Callback<'callback, 'scope>,
+    ) -> Result<Function<'lua>> {
+        let f = mem::transmute::<Callback<'callback, 'scope>, Callback<'lua, 'static>>(f);
+        let f = self.lua.create_callback(f)?;
+
+        let mut destructors = self.destructors.borrow_mut();
+        destructors.push((f.0.clone(), |f| {
+            let state = f.lua.state;
+            assert_stack(state, 3);
+            f.lua.push_ref(&f);
+
+            // We know the destructor has not run yet because we hold a reference to the callback.
+
+            ffi::lua_getupvalue(state, -1, 1);
+            let ud1 = take_userdata::<Callback>(state);
+            ffi::lua_pushnil(state);
+            ffi::lua_setupvalue(state, -2, 1);
+
+            ffi::lua_getupvalue(state, -1, 2);
+            let ud2 = take_userdata::<Lua>(state);
+            ffi::lua_pushnil(state);
+            ffi::lua_setupvalue(state, -2, 2);
+
+            ffi::lua_pop(state, 1);
+            vec![Box::new(ud1), Box::new(ud2)]
+        }));
+        Ok(f)
+    }
+
+    #[cfg(feature = "async")]
+    unsafe fn create_async_callback<'callback>(
+        &self,
+        f: AsyncCallback<'callback, 'scope>,
+    ) -> Result<Function<'lua>> {
+        let f = mem::transmute::<AsyncCallback<'callback, 'scope>, AsyncCallback<'lua, 'static>>(f);
+        let f = self.lua.create_async_callback(f)?;
+
+        let mut destructors = self.destructors.borrow_mut();
+        destructors.push((f.0.clone(), |f| {
+            let state = f.lua.state;
+            assert_stack(state, 4);
+            f.lua.push_ref(&f);
+
+            // We know the destructor has not run yet because we hold a reference to the callback.
+
+            // First, get the environment table
+            #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+            ffi::lua_getupvalue(state, -1, 1);
+            #[cfg(any(feature = "lua51", feature = "luajit"))]
+            ffi::lua_getfenv(state, -1);
+
+            // Second, get the `get_poll()` closure using the corresponding key
+            ffi::lua_pushstring(state, cstr!("get_poll"));
+            ffi::lua_rawget(state, -2);
+
+            // Destroy all upvalues
+            ffi::lua_getupvalue(state, -1, 1);
+            let ud1 = take_userdata::<AsyncCallback>(state);
+            ffi::lua_pushnil(state);
+            ffi::lua_setupvalue(state, -2, 1);
+
+            ffi::lua_getupvalue(state, -1, 2);
+            let ud2 = take_userdata::<Lua>(state);
+            ffi::lua_pushnil(state);
+            ffi::lua_setupvalue(state, -2, 2);
+
+            ffi::lua_pop(state, 1);
+            let mut data: Vec<Box<dyn Any>> = vec![Box::new(ud1), Box::new(ud2)];
+
+            // Finally, get polled future and destroy it
+            ffi::lua_pushstring(state, cstr!("poll"));
+            if ffi::lua_rawget(state, -2) == ffi::LUA_TFUNCTION {
+                ffi::lua_getupvalue(state, -1, 1);
+                let ud3 = take_userdata::<LocalBoxFuture<Result<MultiValue>>>(state);
+                ffi::lua_pushnil(state);
+                ffi::lua_setupvalue(state, -2, 1);
+                data.push(Box::new(ud3));
+
+                ffi::lua_getupvalue(state, -1, 2);
+                let ud4 = take_userdata::<Lua>(state);
+                ffi::lua_pushnil(state);
+                ffi::lua_setupvalue(state, -2, 2);
+                data.push(Box::new(ud4));
+            }
+
+            data
+        }));
+
+        Ok(f)
+    }
+}
+
+impl<'lua, 'scope> Drop for Scope<'lua, 'scope> {
+    fn drop(&mut self) {
+        // We separate the action of invalidating the userdata in Lua and actually dropping the
+        // userdata type into two phases.  This is so that, in the event a userdata drop panics, we
+        // can be sure that all of the userdata in Lua is actually invalidated.
+
+        // All destructors are non-panicking, so this is fine
+        let to_drop = self
+            .destructors
+            .get_mut()
+            .drain(..)
+            .flat_map(|(r, dest)| dest(r))
+            .collect::<Vec<_>>();
+
+        drop(to_drop);
+    }
+}
+
+enum NonStaticMethod<'lua, T> {
+    Method(Box<dyn Fn(&'lua Lua, &T, MultiValue<'lua>) -> Result<MultiValue<'lua>>>),
+    MethodMut(Box<dyn FnMut(&'lua Lua, &mut T, MultiValue<'lua>) -> Result<MultiValue<'lua>>>),
+    Function(Box<dyn Fn(&'lua Lua, MultiValue<'lua>) -> Result<MultiValue<'lua>>>),
+    FunctionMut(Box<dyn FnMut(&'lua Lua, MultiValue<'lua>) -> Result<MultiValue<'lua>>>),
+}
+
+struct NonStaticUserDataMethods<'lua, T: UserData> {
+    methods: Vec<(Vec<u8>, NonStaticMethod<'lua, T>)>,
+    meta_methods: Vec<(MetaMethod, NonStaticMethod<'lua, T>)>,
+}
+
+impl<'lua, T: UserData> Default for NonStaticUserDataMethods<'lua, T> {
+    fn default() -> NonStaticUserDataMethods<'lua, T> {
+        NonStaticUserDataMethods {
+            methods: Vec::new(),
+            meta_methods: Vec::new(),
+        }
+    }
+}
+
+impl<'lua, T: UserData> UserDataMethods<'lua, T> for NonStaticUserDataMethods<'lua, T> {
+    fn add_method<S, A, R, M>(&mut self, name: &S, method: M)
+    where
+        S: AsRef<[u8]> + ?Sized,
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        M: 'static + MaybeSend + Fn(&'lua Lua, &T, A) -> Result<R>,
+    {
+        self.methods.push((
+            name.as_ref().to_vec(),
+            NonStaticMethod::Method(Box::new(move |lua, ud, args| {
+                method(lua, ud, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+
+    fn add_method_mut<S, A, R, M>(&mut self, name: &S, mut method: M)
+    where
+        S: AsRef<[u8]> + ?Sized,
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        M: 'static + MaybeSend + FnMut(&'lua Lua, &mut T, A) -> Result<R>,
+    {
+        self.methods.push((
+            name.as_ref().to_vec(),
+            NonStaticMethod::MethodMut(Box::new(move |lua, ud, args| {
+                method(lua, ud, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+
+    #[cfg(feature = "async")]
+    fn add_async_method<S, A, R, M, MR>(&mut self, _name: &S, _method: M)
+    where
+        T: Clone,
+        S: AsRef<[u8]> + ?Sized,
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        M: 'static + MaybeSend + Fn(&'lua Lua, T, A) -> MR,
+        MR: 'lua + Future<Output = Result<R>>,
+    {
+        // The panic should never happen as async non-static code wouldn't compile
+        // Non-static lifetime must be bounded to 'lua lifetime
+        mlua_panic!("asynchronous methods are not supported for non-static userdata")
+    }
+
+    fn add_function<S, A, R, F>(&mut self, name: &S, function: F)
+    where
+        S: AsRef<[u8]> + ?Sized,
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        F: 'static + MaybeSend + Fn(&'lua Lua, A) -> Result<R>,
+    {
+        self.methods.push((
+            name.as_ref().to_vec(),
+            NonStaticMethod::Function(Box::new(move |lua, args| {
+                function(lua, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+
+    fn add_function_mut<S, A, R, F>(&mut self, name: &S, mut function: F)
+    where
+        S: AsRef<[u8]> + ?Sized,
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        F: 'static + MaybeSend + FnMut(&'lua Lua, A) -> Result<R>,
+    {
+        self.methods.push((
+            name.as_ref().to_vec(),
+            NonStaticMethod::FunctionMut(Box::new(move |lua, args| {
+                function(lua, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+
+    #[cfg(feature = "async")]
+    fn add_async_function<S, A, R, F, FR>(&mut self, _name: &S, _function: F)
+    where
+        T: Clone,
+        S: AsRef<[u8]> + ?Sized,
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        F: 'static + MaybeSend + Fn(&'lua Lua, A) -> FR,
+        FR: 'lua + Future<Output = Result<R>>,
+    {
+        // The panic should never happen as async non-static code wouldn't compile
+        // Non-static lifetime must be bounded to 'lua lifetime
+        mlua_panic!("asynchronous functions are not supported for non-static userdata")
+    }
+
+    fn add_meta_method<A, R, M>(&mut self, meta: MetaMethod, method: M)
+    where
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        M: 'static + MaybeSend + Fn(&'lua Lua, &T, A) -> Result<R>,
+    {
+        self.meta_methods.push((
+            meta,
+            NonStaticMethod::Method(Box::new(move |lua, ud, args| {
+                method(lua, ud, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+
+    fn add_meta_method_mut<A, R, M>(&mut self, meta: MetaMethod, mut method: M)
+    where
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        M: 'static + MaybeSend + FnMut(&'lua Lua, &mut T, A) -> Result<R>,
+    {
+        self.meta_methods.push((
+            meta,
+            NonStaticMethod::MethodMut(Box::new(move |lua, ud, args| {
+                method(lua, ud, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+
+    fn add_meta_function<A, R, F>(&mut self, meta: MetaMethod, function: F)
+    where
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        F: 'static + MaybeSend + Fn(&'lua Lua, A) -> Result<R>,
+    {
+        self.meta_methods.push((
+            meta,
+            NonStaticMethod::Function(Box::new(move |lua, args| {
+                function(lua, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+
+    fn add_meta_function_mut<A, R, F>(&mut self, meta: MetaMethod, mut function: F)
+    where
+        A: FromLuaMulti<'lua>,
+        R: ToLuaMulti<'lua>,
+        F: 'static + MaybeSend + FnMut(&'lua Lua, A) -> Result<R>,
+    {
+        self.meta_methods.push((
+            meta,
+            NonStaticMethod::FunctionMut(Box::new(move |lua, args| {
+                function(lua, A::from_lua_multi(args, lua)?)?.to_lua_multi(lua)
+            })),
+        ));
+    }
+}

src/serde/de.rs

@@ -0,0 +1,329 @@
+use std::string::String as StdString;
+
+use serde::de::{self, IntoDeserializer};
+
+use crate::error::{Error, Result};
+use crate::table::{TablePairs, TableSequence};
+use crate::value::Value;
+
+/// A struct for deserializing Lua values into Rust values.
+pub struct Deserializer<'lua>(pub Value<'lua>);
+
+impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
+    type Error = Error;
+
+    #[inline]
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.0 {
+            Value::Nil => visitor.visit_unit(),
+            Value::Boolean(b) => visitor.visit_bool(b),
+            #[allow(clippy::useless_conversion)]
+            Value::Integer(i) => visitor.visit_i64(i.into()),
+            #[allow(clippy::useless_conversion)]
+            Value::Number(n) => visitor.visit_f64(n.into()),
+            Value::String(s) => match s.to_str() {
+                Ok(s) => visitor.visit_str(s),
+                Err(_) => visitor.visit_bytes(s.as_bytes()),
+            },
+            Value::Table(ref t) if t.raw_len() > 0 || t.is_array() => self.deserialize_seq(visitor),
+            Value::Table(_) => self.deserialize_map(visitor),
+            Value::LightUserData(ud) if ud.0.is_null() => visitor.visit_none(),
+            Value::Function(_)
+            | Value::Thread(_)
+            | Value::UserData(_)
+            | Value::LightUserData(_)
+            | Value::Error(_) => Err(de::Error::custom("invalid value type")),
+        }
+    }
+
+    #[inline]
+    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.0 {
+            Value::Nil => visitor.visit_none(),
+            Value::LightUserData(ud) if ud.0.is_null() => visitor.visit_none(),
+            _ => visitor.visit_some(self),
+        }
+    }
+
+    #[inline]
+    fn deserialize_enum<V>(
+        self,
+        _name: &str,
+        _variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        let (variant, value) = match self.0 {
+            Value::Table(value) => {
+                let mut iter = value.pairs::<StdString, Value>();
+                let (variant, value) = match iter.next() {
+                    Some(v) => v?,
+                    None => {
+                        return Err(de::Error::invalid_value(
+                            de::Unexpected::Map,
+                            &"map with a single key",
+                        ))
+                    }
+                };
+
+                if iter.next().is_some() {
+                    return Err(de::Error::invalid_value(
+                        de::Unexpected::Map,
+                        &"map with a single key",
+                    ));
+                }
+                (variant, Some(value))
+            }
+            Value::String(variant) => (variant.to_str()?.to_owned(), None),
+            _ => return Err(de::Error::custom("bad enum value")),
+        };
+
+        visitor.visit_enum(EnumDeserializer { variant, value })
+    }
+
+    #[inline]
+    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.0 {
+            Value::Table(t) => {
+                let len = t.raw_len() as usize;
+                let mut deserializer = SeqDeserializer(t.raw_sequence_values());
+                let seq = visitor.visit_seq(&mut deserializer)?;
+                if deserializer.0.count() == 0 {
+                    Ok(seq)
+                } else {
+                    Err(de::Error::invalid_length(
+                        len,
+                        &"fewer elements in the table",
+                    ))
+                }
+            }
+            _ => Err(de::Error::custom("invalid value type")),
+        }
+    }
+
+    #[inline]
+    fn deserialize_tuple<V>(self, _len: usize, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        self.deserialize_seq(visitor)
+    }
+
+    #[inline]
+    fn deserialize_tuple_struct<V>(
+        self,
+        _name: &'static str,
+        _len: usize,
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        self.deserialize_seq(visitor)
+    }
+
+    #[inline]
+    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.0 {
+            Value::Table(t) => {
+                let mut deserializer = MapDeserializer::new(t.pairs());
+                let map = visitor.visit_map(&mut deserializer)?;
+                let count = deserializer.pairs.count();
+                if count == 0 {
+                    Ok(map)
+                } else {
+                    Err(de::Error::invalid_length(
+                        deserializer.processed + count,
+                        &"fewer elements in the table",
+                    ))
+                }
+            }
+            _ => Err(de::Error::custom("invalid value type")),
+        }
+    }
+
+    #[inline]
+    fn deserialize_struct<V>(
+        self,
+        _name: &'static str,
+        _fields: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        self.deserialize_map(visitor)
+    }
+
+    serde::forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        byte_buf unit unit_struct newtype_struct
+        identifier ignored_any
+    }
+}
+
+struct SeqDeserializer<'lua>(TableSequence<'lua, Value<'lua>>);
+
+impl<'lua, 'de> de::SeqAccess<'de> for SeqDeserializer<'lua> {
+    type Error = Error;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match self.0.next() {
+            Some(value) => seed.deserialize(Deserializer(value?)).map(Some),
+            None => Ok(None),
+        }
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        match self.0.size_hint() {
+            (lower, Some(upper)) if lower == upper => Some(upper),
+            _ => None,
+        }
+    }
+}
+
+struct MapDeserializer<'lua> {
+    pairs: TablePairs<'lua, Value<'lua>, Value<'lua>>,
+    value: Option<Value<'lua>>,
+    processed: usize,
+}
+
+impl<'lua> MapDeserializer<'lua> {
+    fn new(pairs: TablePairs<'lua, Value<'lua>, Value<'lua>>) -> Self {
+        MapDeserializer {
+            pairs,
+            value: None,
+            processed: 0,
+        }
+    }
+}
+
+impl<'lua, 'de> de::MapAccess<'de> for MapDeserializer<'lua> {
+    type Error = Error;
+
+    fn next_key_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match self.pairs.next() {
+            Some(item) => {
+                let (key, value) = item?;
+                self.processed += 1;
+                self.value = Some(value);
+                let key_de = Deserializer(key);
+                seed.deserialize(key_de).map(Some)
+            }
+            None => Ok(None),
+        }
+    }
+
+    fn next_value_seed<T>(&mut self, seed: T) -> Result<T::Value>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match self.value.take() {
+            Some(value) => seed.deserialize(Deserializer(value)),
+            None => Err(de::Error::custom("value is missing")),
+        }
+    }
+
+    fn size_hint(&self) -> Option<usize> {
+        match self.pairs.size_hint() {
+            (lower, Some(upper)) if lower == upper => Some(upper),
+            _ => None,
+        }
+    }
+}
+
+struct EnumDeserializer<'lua> {
+    variant: StdString,
+    value: Option<Value<'lua>>,
+}
+
+impl<'lua, 'de> de::EnumAccess<'de> for EnumDeserializer<'lua> {
+    type Error = Error;
+    type Variant = VariantDeserializer<'lua>;
+
+    fn variant_seed<T>(self, seed: T) -> Result<(T::Value, Self::Variant)>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        let variant = self.variant.into_deserializer();
+        let variant_access = VariantDeserializer { value: self.value };
+        seed.deserialize(variant).map(|v| (v, variant_access))
+    }
+}
+
+struct VariantDeserializer<'lua> {
+    value: Option<Value<'lua>>,
+}
+
+impl<'lua, 'de> de::VariantAccess<'de> for VariantDeserializer<'lua> {
+    type Error = Error;
+
+    fn unit_variant(self) -> Result<()> {
+        match self.value {
+            Some(_) => Err(de::Error::invalid_type(
+                de::Unexpected::NewtypeVariant,
+                &"unit variant",
+            )),
+            None => Ok(()),
+        }
+    }
+
+    fn newtype_variant_seed<T>(self, seed: T) -> Result<T::Value>
+    where
+        T: de::DeserializeSeed<'de>,
+    {
+        match self.value {
+            Some(value) => seed.deserialize(Deserializer(value)),
+            None => Err(de::Error::invalid_type(
+                de::Unexpected::UnitVariant,
+                &"newtype variant",
+            )),
+        }
+    }
+
+    fn tuple_variant<V>(self, _len: usize, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.value {
+            Some(value) => serde::Deserializer::deserialize_seq(Deserializer(value), visitor),
+            None => Err(de::Error::invalid_type(
+                de::Unexpected::UnitVariant,
+                &"tuple variant",
+            )),
+        }
+    }
+
+    fn struct_variant<V>(self, _fields: &'static [&'static str], visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.value {
+            Some(value) => serde::Deserializer::deserialize_map(Deserializer(value), visitor),
+            None => Err(de::Error::invalid_type(
+                de::Unexpected::UnitVariant,
+                &"struct variant",
+            )),
+        }
+    }
+}

src/serde/mod.rs

@@ -0,0 +1,200 @@
+//! (De)Serialization support using serde.
+
+use std::os::raw::{c_int, c_void};
+use std::ptr;
+
+use serde::{Deserialize, Serialize};
+
+use crate::error::Result;
+use crate::ffi;
+use crate::lua::Lua;
+use crate::table::Table;
+use crate::util::{assert_stack, protect_lua, StackGuard};
+use crate::value::Value;
+
+pub trait LuaSerdeExt<'lua> {
+    /// A special value (lightuserdata) to encode/decode optional (none) values.
+    ///
+    /// Requires `feature = "serialize"`
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use std::collections::HashMap;
+    /// use mlua::{Lua, Result, LuaSerdeExt};
+    ///
+    /// fn main() -> Result<()> {
+    ///     let lua = Lua::new();
+    ///     lua.globals().set("null", lua.null()?)?;
+    ///
+    ///     let val = lua.load(r#"{a = null}"#).eval()?;
+    ///     let map: HashMap<String, Option<String>> = lua.from_value(val)?;
+    ///     assert_eq!(map["a"], None);
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    fn null(&'lua self) -> Result<Value<'lua>>;
+
+    /// A metatable attachable to a Lua table to systematically encode it as Array (instead of Map).
+    /// As result, encoded Array will contain only sequence part of the table, with the same length
+    /// as the `#` operator on that table.
+    ///
+    /// Requires `feature = "serialize"`
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use mlua::{Lua, Result, LuaSerdeExt};
+    /// use serde_json::Value as JsonValue;
+    ///
+    /// fn main() -> Result<()> {
+    ///     let lua = Lua::new();
+    ///     lua.globals().set("array_mt", lua.array_metatable()?)?;
+    ///
+    ///     // Encode as an empty array (no sequence part in the lua table)
+    ///     let val = lua.load("setmetatable({a = 5}, array_mt)").eval()?;
+    ///     let j: JsonValue = lua.from_value(val)?;
+    ///     assert_eq!(j.to_string(), "[]");
+    ///
+    ///     // Encode as object
+    ///     let val = lua.load("{a = 5}").eval()?;
+    ///     let j: JsonValue = lua.from_value(val)?;
+    ///     assert_eq!(j.to_string(), r#"{"a":5}"#);
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    fn array_metatable(&'lua self) -> Result<Table<'lua>>;
+
+    /// Converts `T` into a `Value` instance.
+    ///
+    /// Requires `feature = "serialize"`
+    ///
+    /// [`Value`]: enum.Value.html
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use mlua::{Lua, Result, LuaSerdeExt};
+    /// use serde::Serialize;
+    ///
+    /// #[derive(Serialize)]
+    /// struct User {
+    ///     name: String,
+    ///     age: u8,
+    /// }
+    ///
+    /// fn main() -> Result<()> {
+    ///     let lua = Lua::new();
+    ///     let u = User {
+    ///         name: "John Smith".into(),
+    ///         age: 20,
+    ///     };
+    ///     lua.globals().set("user", lua.to_value(&u)?)?;
+    ///     lua.load(r#"
+    ///         assert(user["name"] == "John Smith")
+    ///         assert(user["age"] == 20)
+    ///     "#).exec()
+    /// }
+    /// ```
+    fn to_value<T: Serialize + ?Sized>(&'lua self, t: &T) -> Result<Value<'lua>>;
+
+    /// Deserializes a `Value` into any serde deserializable object.
+    ///
+    /// Requires `feature = "serialize"`
+    ///
+    /// [`Value`]: enum.Value.html
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use mlua::{Lua, Result, LuaSerdeExt};
+    /// use serde::Deserialize;
+    ///
+    /// #[derive(Deserialize, Debug, PartialEq)]
+    /// struct User {
+    ///     name: String,
+    ///     age: u8,
+    /// }
+    ///
+    /// fn main() -> Result<()> {
+    ///     let lua = Lua::new();
+    ///     let val = lua.load(r#"{name = "John Smith", age = 20}"#).eval()?;
+    ///     let u: User = lua.from_value(val)?;
+    ///
+    ///     assert_eq!(u, User { name: "John Smith".into(), age: 20 });
+    ///
+    ///     Ok(())
+    /// }
+    /// ```
+    fn from_value<T: Deserialize<'lua>>(&'lua self, value: Value<'lua>) -> Result<T>;
+}
+
+impl<'lua> LuaSerdeExt<'lua> for Lua {
+    fn null(&'lua self) -> Result<Value<'lua>> {
+        unsafe {
+            let _sg = StackGuard::new(self.state);
+            assert_stack(self.state, 3);
+
+            unsafe extern "C" fn push_null(state: *mut ffi::lua_State) -> c_int {
+                ffi::lua_pushlightuserdata(state, ptr::null_mut());
+                1
+            }
+            protect_lua(self.state, 0, push_null)?;
+            Ok(self.pop_value())
+        }
+    }
+
+    fn array_metatable(&'lua self) -> Result<Table<'lua>> {
+        unsafe {
+            let _sg = StackGuard::new(self.state);
+            assert_stack(self.state, 3);
+
+            unsafe extern "C" fn get_array_mt(state: *mut ffi::lua_State) -> c_int {
+                push_array_metatable(state);
+                1
+            }
+            protect_lua(self.state, 0, get_array_mt)?;
+            Ok(Table(self.pop_ref()))
+        }
+    }
+
+    fn to_value<T>(&'lua self, t: &T) -> Result<Value<'lua>>
+    where
+        T: Serialize + ?Sized,
+    {
+        t.serialize(ser::Serializer(self))
+    }
+
+    fn from_value<T>(&'lua self, value: Value<'lua>) -> Result<T>
+    where
+        T: Deserialize<'lua>,
+    {
+        T::deserialize(de::Deserializer(value))
+    }
+}
+
+pub(crate) unsafe fn init_metatables(state: *mut ffi::lua_State) {
+    ffi::lua_pushlightuserdata(
+        state,
+        &ARRAY_METATABLE_REGISTRY_KEY as *const u8 as *mut c_void,
+    );
+    ffi::lua_newtable(state);
+
+    ffi::lua_pushstring(state, cstr!("__metatable"));
+    ffi::lua_pushboolean(state, 0);
+    ffi::lua_rawset(state, -3);
+
+    ffi::lua_rawset(state, ffi::LUA_REGISTRYINDEX);
+}
+
+pub(crate) unsafe fn push_array_metatable(state: *mut ffi::lua_State) {
+    let key = &ARRAY_METATABLE_REGISTRY_KEY as *const u8 as *mut c_void;
+    ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, key);
+}
+
+static ARRAY_METATABLE_REGISTRY_KEY: u8 = 0;
+
+pub mod de;
+pub mod ser;

src/serde/ser.rs

@@ -0,0 +1,366 @@
+use std::os::raw::c_int;
+
+use serde::{ser, Serialize};
+
+use super::LuaSerdeExt;
+use crate::error::{Error, Result};
+use crate::ffi;
+use crate::lua::Lua;
+use crate::string::String;
+use crate::table::Table;
+use crate::types::Integer;
+use crate::util::{assert_stack, protect_lua, StackGuard};
+use crate::value::{ToLua, Value};
+
+/// A struct for serializing Rust values into Lua values.
+pub struct Serializer<'lua>(pub &'lua Lua);
+
+macro_rules! lua_serialize_number {
+    ($name:ident, $t:ty) => {
+        #[inline]
+        fn $name(self, value: $t) -> Result<Value<'lua>> {
+            value.to_lua(self.0)
+        }
+    };
+}
+
+impl<'lua> ser::Serializer for Serializer<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    // Associated types for keeping track of additional state while serializing
+    // compound data structures like sequences and maps.
+    type SerializeSeq = SerializeVec<'lua>;
+    type SerializeTuple = SerializeVec<'lua>;
+    type SerializeTupleStruct = SerializeVec<'lua>;
+    type SerializeTupleVariant = SerializeTupleVariant<'lua>;
+    type SerializeMap = SerializeMap<'lua>;
+    type SerializeStruct = SerializeMap<'lua>;
+    type SerializeStructVariant = SerializeStructVariant<'lua>;
+
+    #[inline]
+    fn serialize_bool(self, value: bool) -> Result<Value<'lua>> {
+        Ok(Value::Boolean(value))
+    }
+
+    lua_serialize_number!(serialize_i8, i8);
+    lua_serialize_number!(serialize_u8, u8);
+    lua_serialize_number!(serialize_i16, i16);
+    lua_serialize_number!(serialize_u16, u16);
+    lua_serialize_number!(serialize_i32, i32);
+    lua_serialize_number!(serialize_u32, u32);
+    lua_serialize_number!(serialize_i64, i64);
+    lua_serialize_number!(serialize_u64, u64);
+
+    lua_serialize_number!(serialize_f32, f32);
+    lua_serialize_number!(serialize_f64, f64);
+
+    #[inline]
+    fn serialize_char(self, value: char) -> Result<Value<'lua>> {
+        self.serialize_str(&value.to_string())
+    }
+
+    #[inline]
+    fn serialize_str(self, value: &str) -> Result<Value<'lua>> {
+        self.0.create_string(value).map(Value::String)
+    }
+
+    #[inline]
+    fn serialize_bytes(self, value: &[u8]) -> Result<Value<'lua>> {
+        self.0.create_string(value).map(Value::String)
+    }
+
+    #[inline]
+    fn serialize_none(self) -> Result<Value<'lua>> {
+        self.0.null()
+    }
+
+    #[inline]
+    fn serialize_some<T>(self, value: &T) -> Result<Value<'lua>>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(self)
+    }
+
+    #[inline]
+    fn serialize_unit(self) -> Result<Value<'lua>> {
+        self.0.null()
+    }
+
+    #[inline]
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<Value<'lua>> {
+        self.0.null()
+    }
+
+    #[inline]
+    fn serialize_unit_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+    ) -> Result<Value<'lua>> {
+        self.serialize_str(variant)
+    }
+
+    #[inline]
+    fn serialize_newtype_struct<T>(self, _name: &'static str, value: &T) -> Result<Value<'lua>>
+    where
+        T: ?Sized + Serialize,
+    {
+        value.serialize(self)
+    }
+
+    #[inline]
+    fn serialize_newtype_variant<T>(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+        value: &T,
+    ) -> Result<Value<'lua>>
+    where
+        T: ?Sized + Serialize,
+    {
+        let table = self.0.create_table()?;
+        let variant = self.0.create_string(variant)?;
+        let value = self.0.to_value(value)?;
+        table.raw_set(variant, value)?;
+        Ok(Value::Table(table))
+    }
+
+    #[inline]
+    fn serialize_seq(self, len: Option<usize>) -> Result<Self::SerializeSeq> {
+        let len = len.unwrap_or(0) as c_int;
+        let table = self.0.create_table_with_capacity(len, 0)?;
+        table.set_metatable(Some(self.0.array_metatable()?));
+        Ok(SerializeVec { table })
+    }
+
+    #[inline]
+    fn serialize_tuple(self, len: usize) -> Result<Self::SerializeTuple> {
+        self.serialize_seq(Some(len))
+    }
+
+    #[inline]
+    fn serialize_tuple_struct(
+        self,
+        _name: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeTupleStruct> {
+        self.serialize_seq(Some(len))
+    }
+
+    #[inline]
+    fn serialize_tuple_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeTupleVariant> {
+        let name = self.0.create_string(variant)?;
+        let table = self.0.create_table()?;
+        Ok(SerializeTupleVariant { name, table })
+    }
+
+    #[inline]
+    fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap> {
+        let len = len.unwrap_or(0) as c_int;
+        Ok(SerializeMap {
+            key: None,
+            table: self.0.create_table_with_capacity(0, len)?,
+        })
+    }
+
+    #[inline]
+    fn serialize_struct(self, _name: &'static str, len: usize) -> Result<Self::SerializeStruct> {
+        self.serialize_map(Some(len))
+    }
+
+    #[inline]
+    fn serialize_struct_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeStructVariant> {
+        let name = self.0.create_string(variant)?;
+        let table = self.0.create_table_with_capacity(0, len as c_int)?;
+        Ok(SerializeStructVariant { name, table })
+    }
+}
+
+pub struct SerializeVec<'lua> {
+    table: Table<'lua>,
+}
+
+impl<'lua> ser::SerializeSeq for SerializeVec<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        let lua = self.table.0.lua;
+        let value = lua.to_value(value)?;
+        unsafe {
+            let _sg = StackGuard::new(lua.state);
+            assert_stack(lua.state, 4);
+
+            lua.push_ref(&self.table.0);
+            lua.push_value(value)?;
+
+            unsafe extern "C" fn push_to_table(state: *mut ffi::lua_State) -> c_int {
+                let len = ffi::lua_rawlen(state, -2) as Integer;
+                ffi::lua_rawseti(state, -2, len + 1);
+                1
+            }
+
+            protect_lua(lua.state, 2, push_to_table)
+        }
+    }
+
+    fn end(self) -> Result<Value<'lua>> {
+        Ok(Value::Table(self.table))
+    }
+}
+
+impl<'lua> ser::SerializeTuple for SerializeVec<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeSeq::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<Value<'lua>> {
+        ser::SerializeSeq::end(self)
+    }
+}
+
+impl<'lua> ser::SerializeTupleStruct for SerializeVec<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeSeq::serialize_element(self, value)
+    }
+
+    fn end(self) -> Result<Value<'lua>> {
+        ser::SerializeSeq::end(self)
+    }
+}
+
+pub struct SerializeTupleVariant<'lua> {
+    name: String<'lua>,
+    table: Table<'lua>,
+}
+
+impl<'lua> ser::SerializeTupleVariant for SerializeTupleVariant<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        let lua = self.table.0.lua;
+        let idx = self.table.raw_len() + 1;
+        self.table.raw_insert(idx, lua.to_value(value)?)
+    }
+
+    fn end(self) -> Result<Value<'lua>> {
+        let lua = self.table.0.lua;
+        let table = lua.create_table()?;
+        table.raw_set(self.name, self.table)?;
+        Ok(Value::Table(table))
+    }
+}
+
+pub struct SerializeMap<'lua> {
+    table: Table<'lua>,
+    key: Option<Value<'lua>>,
+}
+
+impl<'lua> ser::SerializeMap for SerializeMap<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    fn serialize_key<T>(&mut self, key: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        let lua = self.table.0.lua;
+        self.key = Some(lua.to_value(key)?);
+        Ok(())
+    }
+
+    fn serialize_value<T>(&mut self, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        let lua = self.table.0.lua;
+        let key = mlua_expect!(
+            self.key.take(),
+            "serialize_value called before serialize_key"
+        );
+        let value = lua.to_value(value)?;
+        self.table.raw_set(key, value)
+    }
+
+    fn end(self) -> Result<Value<'lua>> {
+        Ok(Value::Table(self.table))
+    }
+}
+
+impl<'lua> ser::SerializeStruct for SerializeMap<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        ser::SerializeMap::serialize_key(self, key)?;
+        ser::SerializeMap::serialize_value(self, value)
+    }
+
+    fn end(self) -> Result<Value<'lua>> {
+        ser::SerializeMap::end(self)
+    }
+}
+
+pub struct SerializeStructVariant<'lua> {
+    name: String<'lua>,
+    table: Table<'lua>,
+}
+
+impl<'lua> ser::SerializeStructVariant for SerializeStructVariant<'lua> {
+    type Ok = Value<'lua>;
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, key: &'static str, value: &T) -> Result<()>
+    where
+        T: ?Sized + Serialize,
+    {
+        let lua = self.table.0.lua;
+        self.table.raw_set(key, lua.to_value(value)?)?;
+        Ok(())
+    }
+
+    fn end(self) -> Result<Value<'lua>> {
+        let lua = self.table.0.lua;
+        let table = lua.create_table()?;
+        table.raw_set(self.name, self.table)?;
+        Ok(Value::Table(table))
+    }
+}

src/stdlib.rs

@@ -1,31 +1,58 @@
 use std::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign};
 use std::u32;
 
-/// Flags describing the set of lua modules to load.
+/// Flags describing the set of lua standard libraries to load.
 #[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
 pub struct StdLib(u32);
 
 impl StdLib {
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
-    pub const COROUTINE: StdLib = StdLib(1 << 0);
+    /// [`coroutine`](https://www.lua.org/manual/5.3/manual.html#6.2) library
+    ///
+    /// Requires `feature = "lua54/lua53/lua52"`
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", doc))]
+    pub const COROUTINE: StdLib = StdLib(1);
+    /// [`table`](https://www.lua.org/manual/5.3/manual.html#6.6) library
     pub const TABLE: StdLib = StdLib(1 << 1);
+    /// [`io`](https://www.lua.org/manual/5.3/manual.html#6.8) library
     pub const IO: StdLib = StdLib(1 << 2);
+    /// [`os`](https://www.lua.org/manual/5.3/manual.html#6.9) library
     pub const OS: StdLib = StdLib(1 << 3);
+    /// [`string`](https://www.lua.org/manual/5.3/manual.html#6.4) library
     pub const STRING: StdLib = StdLib(1 << 4);
-    #[cfg(feature = "lua53")]
+    /// [`utf8`](https://www.lua.org/manual/5.3/manual.html#6.5) library
+    ///
+    /// Requires `feature = "lua54/lua53"`
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     pub const UTF8: StdLib = StdLib(1 << 5);
-    #[cfg(any(feature = "lua52", feature = "luajit"))]
+    /// [`bit`](https://www.lua.org/manual/5.2/manual.html#6.7) library
+    ///
+    /// Requires `feature = "lua52/luajit"`
+    #[cfg(any(feature = "lua52", feature = "luajit", doc))]
     pub const BIT: StdLib = StdLib(1 << 6);
+    /// [`math`](https://www.lua.org/manual/5.3/manual.html#6.7) library
     pub const MATH: StdLib = StdLib(1 << 7);
+    /// [`package`](https://www.lua.org/manual/5.3/manual.html#6.3) library
     pub const PACKAGE: StdLib = StdLib(1 << 8);
-    #[cfg(feature = "luajit")]
+    /// [`jit`](http://luajit.org/ext_jit.html) library
+    ///
+    /// Requires `feature = "luajit"`
+    #[cfg(any(feature = "luajit", doc))]
     pub const JIT: StdLib = StdLib(1 << 9);
-    #[cfg(feature = "luajit")]
-    pub const FFI: StdLib = StdLib(1 << 10);
-    pub const DEBUG: StdLib = StdLib(1 << 31); // always highest bit
 
+    /// (unsafe) [`ffi`](http://luajit.org/ext_ffi.html) library
+    ///
+    /// Requires `feature = "luajit"`
+    #[cfg(any(feature = "luajit", doc))]
+    pub const FFI: StdLib = StdLib(1 << 30);
+    /// (unsafe) [`debug`](https://www.lua.org/manual/5.3/manual.html#6.10) library
+    pub const DEBUG: StdLib = StdLib(1 << 31);
+
+    /// No libraries
+    pub const NONE: StdLib = StdLib(0);
+    /// (unsafe) All standard libraries
     pub const ALL: StdLib = StdLib(u32::MAX);
-    pub const ALL_NO_DEBUG: StdLib = StdLib((1 << 31) - 1);
+    /// The safe subset of the standard libraries
+    pub const ALL_SAFE: StdLib = StdLib((1 << 30) - 1);
 
     pub fn contains(self, lib: Self) -> bool {
         (self & lib).0 != 0

src/string.rs

@@ -1,5 +1,11 @@
 use std::{slice, str};
 
+#[cfg(feature = "serialize")]
+use {
+    serde::ser::{Serialize, Serializer},
+    std::result::Result as StdResult,
+};
+
 use crate::error::{Error, Result};
 use crate::ffi;
 use crate::types::LuaRef;
@@ -105,3 +111,16 @@ where
         self.as_bytes() == other.as_ref()
     }
 }
+
+#[cfg(feature = "serialize")]
+impl<'lua> Serialize for String<'lua> {
+    fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self.to_str() {
+            Ok(s) => serializer.serialize_str(s),
+            Err(_) => serializer.serialize_bytes(self.as_bytes()),
+        }
+    }
+}

src/table.rs

@@ -1,6 +1,12 @@
 use std::marker::PhantomData;
 use std::os::raw::c_int;
 
+#[cfg(feature = "serialize")]
+use {
+    serde::ser::{Serialize, SerializeMap, SerializeSeq, Serializer},
+    std::result::Result as StdResult,
+};
+
 use crate::error::{Error, Result};
 use crate::ffi;
 use crate::function::Function;
@@ -15,6 +21,7 @@ use {futures_core::future::LocalBoxFuture, futures_util::future};
 #[derive(Clone, Debug)]
 pub struct Table<'lua>(pub(crate) LuaRef<'lua>);
 
+#[allow(clippy::len_without_is_empty)]
 impl<'lua> Table<'lua> {
     /// Sets a key-value pair in the table.
     ///
@@ -136,28 +143,6 @@ impl<'lua> Table<'lua> {
         }
     }
 
-    /// Gets the function associated to `key` from the table and executes it,
-    /// passing the table itself along with `args` as function arguments.
-    ///
-    /// This function is deprecated since 0.3.1 in favor of [`call_method`]
-    /// in the `TableExt` trait.
-    ///
-    /// This might invoke the `__index` metamethod.
-    ///
-    /// [`call_method`]: trait.TableExt.html#tymethod.call_method
-    #[deprecated(since = "0.3.1", note = "Please use `call_method` instead")]
-    pub fn call<K, A, R>(&self, key: K, args: A) -> Result<R>
-    where
-        K: ToLua<'lua>,
-        A: ToLuaMulti<'lua>,
-        R: FromLuaMulti<'lua>,
-    {
-        let lua = self.0.lua;
-        let mut args = args.to_lua_multi(lua)?;
-        args.push_front(Value::Table(self.clone()));
-        self.get::<_, Function>(key)?.call(args)
-    }
-
     /// Compares two tables for equality.
     ///
     /// Tables are compared by reference first.
@@ -468,9 +453,56 @@ impl<'lua> Table<'lua> {
         TableSequence {
             table: self.0,
             index: Some(1),
+            len: None,
+            raw: false,
             _phantom: PhantomData,
         }
     }
+
+    /// Consume this table and return an iterator over all values in the sequence part of the table.
+    ///
+    /// Unlike the `sequence_values`, does not invoke `__index` metamethod when iterating.
+    ///
+    /// [`sequence_values`]: #method.sequence_values
+    pub fn raw_sequence_values<V: FromLua<'lua>>(self) -> TableSequence<'lua, V> {
+        TableSequence {
+            table: self.0,
+            index: Some(1),
+            len: None,
+            raw: true,
+            _phantom: PhantomData,
+        }
+    }
+
+    #[cfg(any(feature = "async", feature = "serialize"))]
+    pub(crate) fn raw_sequence_values_by_len<V: FromLua<'lua>>(
+        self,
+        len: Option<Integer>,
+    ) -> TableSequence<'lua, V> {
+        let len = len.unwrap_or_else(|| self.raw_len());
+        TableSequence {
+            table: self.0,
+            index: Some(1),
+            len: Some(len),
+            raw: true,
+            _phantom: PhantomData,
+        }
+    }
+
+    #[cfg(feature = "serialize")]
+    pub(crate) fn is_array(&self) -> bool {
+        let lua = self.0.lua;
+        unsafe {
+            let _sg = StackGuard::new(lua.state);
+            assert_stack(lua.state, 3);
+            lua.push_ref(&self.0);
+            if ffi::lua_getmetatable(lua.state, -1) == 0 {
+                return false;
+            }
+            crate::serde::push_array_metatable(lua.state);
+            ffi::lua_rawequal(lua.state, -1, -2) != 0
+        }
+    }
 }
 
 impl<'lua> PartialEq for Table<'lua> {
@@ -517,8 +549,11 @@ pub trait TableExt<'lua> {
     /// Gets the function associated to `key` from the table and asynchronously executes it,
     /// passing the table itself along with `args` as function arguments and returning Future.
     ///
+    /// Requires `feature = "async"`
+    ///
     /// This might invoke the `__index` metamethod.
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     fn call_async_method<'fut, K, A, R>(&self, key: K, args: A) -> LocalBoxFuture<'fut, Result<R>>
     where
         'lua: 'fut,
@@ -529,8 +564,11 @@ pub trait TableExt<'lua> {
     /// Gets the function associated to `key` from the table and asynchronously executes it,
     /// passing `args` as function arguments and returning Future.
     ///
+    /// Requires `feature = "async"`
+    ///
     /// This might invoke the `__index` metamethod.
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     fn call_async_function<'fut, K, A, R>(
         &self,
         key: K,
@@ -597,6 +635,31 @@ impl<'lua> TableExt<'lua> for Table<'lua> {
     }
 }
 
+#[cfg(feature = "serialize")]
+impl<'lua> Serialize for Table<'lua> {
+    fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let len = self.raw_len() as usize;
+        if len > 0 || self.is_array() {
+            let mut seq = serializer.serialize_seq(Some(len))?;
+            for v in self.clone().raw_sequence_values_by_len::<Value>(None) {
+                let v = v.map_err(serde::ser::Error::custom)?;
+                seq.serialize_element(&v)?;
+            }
+            return seq.end();
+        }
+
+        let mut map = serializer.serialize_map(None)?;
+        for kv in self.clone().pairs::<Value, Value>() {
+            let (k, v) = kv.map_err(serde::ser::Error::custom)?;
+            map.serialize_entry(&k, &v)?;
+        }
+        map.end()
+    }
+}
+
 /// An iterator over the pairs of a Lua table.
 ///
 /// This struct is created by the [`Table::pairs`] method.
@@ -627,9 +690,10 @@ where
                     lua.push_ref(&self.table);
                     lua.push_value(next_key)?;
 
-                    if protect_lua_closure(lua.state, 2, ffi::LUA_MULTRET, |state| {
+                    let next = protect_lua_closure(lua.state, 2, ffi::LUA_MULTRET, |state| {
                         ffi::lua_next(state, -2) != 0
-                    })? {
+                    })?;
+                    if next {
                         ffi::lua_pushvalue(lua.state, -2);
                         let key = lua.pop_value();
                         let value = lua.pop_value();
@@ -667,6 +731,8 @@ where
 pub struct TableSequence<'lua, V> {
     table: LuaRef<'lua>,
     index: Option<Integer>,
+    len: Option<Integer>,
+    raw: bool,
     _phantom: PhantomData<V>,
 }
 
@@ -685,9 +751,13 @@ where
                 assert_stack(lua.state, 5);
 
                 lua.push_ref(&self.table);
-                match protect_lua_closure(lua.state, 1, 1, |state| ffi::lua_geti(state, -1, index))
-                {
-                    Ok(ffi::LUA_TNIL) => None,
+                let lua_geti = if self.raw {
+                    ffi::lua_rawgeti
+                } else {
+                    ffi::lua_geti
+                };
+                match protect_lua_closure(lua.state, 1, 1, |state| lua_geti(state, -1, index)) {
+                    Ok(ffi::LUA_TNIL) if index > self.len.unwrap_or(0) => None,
                     Ok(_) => {
                         let value = lua.pop_value();
                         self.index = Some(index + 1);

src/thread.rs

@@ -47,9 +47,12 @@ pub struct Thread<'lua>(pub(crate) LuaRef<'lua>);
 
 /// Thread (coroutine) representation as an async [`Future`] or [`Stream`].
 ///
+/// Requires `feature = "async"`
+///
 /// [`Future`]: ../futures_core/future/trait.Future.html
 /// [`Stream`]: ../futures_core/stream/trait.Stream.html
 #[cfg(feature = "async")]
+#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
 #[derive(Debug)]
 pub struct AsyncThread<'lua, R> {
     thread: Thread<'lua>,
@@ -129,7 +132,9 @@ impl<'lua> Thread<'lua> {
             }
             ffi::lua_xmove(lua.state, thread_state, nargs);
 
-            let ret = ffi::lua_resume(thread_state, lua.state, nargs);
+            let mut nresults = 0;
+
+            let ret = ffi::lua_resume(thread_state, lua.state, nargs, &mut nresults as *mut c_int);
             if ret != ffi::LUA_OK && ret != ffi::LUA_YIELD {
                 protect_lua_closure(lua.state, 0, 0, |_| {
                     error_traceback(thread_state);
@@ -138,7 +143,6 @@ impl<'lua> Thread<'lua> {
                 return Err(pop_error(thread_state, ret));
             }
 
-            let nresults = ffi::lua_gettop(thread_state);
             let mut results = MultiValue::new();
             ffi::lua_xmove(thread_state, lua.state, nresults);
 
@@ -183,6 +187,8 @@ impl<'lua> Thread<'lua> {
     /// values whereas Future version discards that values and poll until the final
     /// one (returned from the thread function).
     ///
+    /// Requires `feature = "async"`
+    ///
     /// # Examples
     ///
     /// ```
@@ -213,6 +219,7 @@ impl<'lua> Thread<'lua> {
     /// # }
     /// ```
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub fn into_async<A, R>(self, args: A) -> AsyncThread<'lua, R>
     where
         A: ToLuaMulti<'lua>,

src/types.rs

@@ -1,6 +1,6 @@
 use std::cell::RefCell;
 use std::os::raw::{c_int, c_void};
-use std::rc::Rc;
+use std::sync::{Arc, Mutex};
 use std::{fmt, mem, ptr};
 
 #[cfg(feature = "async")]
@@ -8,7 +8,9 @@ use futures_core::future::LocalBoxFuture;
 
 use crate::error::Result;
 use crate::ffi;
+use crate::hook::Debug;
 use crate::lua::Lua;
+use crate::userdata::UserDataWrapped;
 use crate::util::{assert_stack, StackGuard};
 use crate::value::MultiValue;
 
@@ -28,6 +30,20 @@ pub(crate) type Callback<'lua, 'a> =
 pub(crate) type AsyncCallback<'lua, 'a> =
     Box<dyn Fn(&'lua Lua, MultiValue<'lua>) -> LocalBoxFuture<'lua, Result<MultiValue<'lua>>> + 'a>;
 
+pub(crate) type HookCallback = Arc<RefCell<dyn FnMut(&Lua, Debug) -> Result<()>>>;
+
+pub(crate) type UserDataCell<T> = RefCell<UserDataWrapped<T>>;
+
+#[cfg(feature = "send")]
+pub trait MaybeSend: Send {}
+#[cfg(feature = "send")]
+impl<T: Send> MaybeSend for T {}
+
+#[cfg(not(feature = "send"))]
+pub trait MaybeSend {}
+#[cfg(not(feature = "send"))]
+impl<T> MaybeSend for T {}
+
 /// An auto generated key into the Lua registry.
 ///
 /// This is a handle to a value stored inside the Lua registry.  It is not automatically
@@ -45,7 +61,7 @@ pub(crate) type AsyncCallback<'lua, 'a> =
 /// [`UserData::get_user_value`]: struct.UserData.html#method.get_user_value
 pub struct RegistryKey {
     pub(crate) registry_id: c_int,
-    pub(crate) unref_list: Rc<RefCell<Option<Vec<c_int>>>>,
+    pub(crate) unref_list: Arc<Mutex<Option<Vec<c_int>>>>,
 }
 
 impl fmt::Debug for RegistryKey {
@@ -56,7 +72,7 @@ impl fmt::Debug for RegistryKey {
 
 impl Drop for RegistryKey {
     fn drop(&mut self) {
-        let mut unref_list = mlua_expect!(self.unref_list.try_borrow_mut(), "unref list borrowed");
+        let mut unref_list = mlua_expect!(self.unref_list.lock(), "unref list poisoned");
         if let Some(list) = unref_list.as_mut() {
             list.push(self.registry_id);
         }

src/userdata.rs

@@ -1,16 +1,22 @@
-use std::cell::{Ref, RefCell, RefMut};
+use std::cell::{Ref, RefMut};
 
 #[cfg(feature = "async")]
 use std::future::Future;
 
+#[cfg(feature = "serialize")]
+use {
+    serde::ser::{self, Serialize, Serializer},
+    std::result::Result as StdResult,
+};
+
 use crate::error::{Error, Result};
 use crate::ffi;
 use crate::function::Function;
 use crate::lua::Lua;
 use crate::table::Table;
-use crate::types::LuaRef;
-use crate::util::{assert_stack, get_userdata, StackGuard};
-use crate::value::{FromLua, FromLuaMulti, ToLua, ToLuaMulti};
+use crate::types::{LuaRef, MaybeSend, UserDataCell};
+use crate::util::{assert_stack, get_destructed_userdata_metatable, get_userdata, StackGuard};
+use crate::value::{FromLua, FromLuaMulti, ToLua, ToLuaMulti, Value};
 
 /// Kinds of metamethods that can be overridden.
 ///
@@ -34,26 +40,31 @@ pub enum MetaMethod {
     Pow,
     /// The unary minus (`-`) operator.
     Unm,
-    #[cfg(feature = "lua53")]
     /// The floor division (//) operator.
+    /// Requires `feature = "lua54/lua53"`
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     IDiv,
-    #[cfg(feature = "lua53")]
     /// The bitwise AND (&) operator.
+    /// Requires `feature = "lua54/lua53"`
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     BAnd,
-    #[cfg(feature = "lua53")]
     /// The bitwise OR (|) operator.
+    /// Requires `feature = "lua54/lua53"`
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     BOr,
-    #[cfg(feature = "lua53")]
     /// The bitwise XOR (binary ~) operator.
+    /// Requires `feature = "lua54/lua53"`
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     BXor,
-    #[cfg(feature = "lua53")]
     /// The bitwise NOT (unary ~) operator.
+    /// Requires `feature = "lua54/lua53"`
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     BNot,
-    #[cfg(feature = "lua53")]
     /// The bitwise left shift (<<) operator.
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     Shl,
-    #[cfg(feature = "lua53")]
     /// The bitwise right shift (>>) operator.
+    #[cfg(any(feature = "lua54", feature = "lua53", doc))]
     Shr,
     /// The string concatenation operator `..`.
     Concat,
@@ -75,11 +86,25 @@ pub enum MetaMethod {
     ///
     /// This is not an operator, but will be called by methods such as `tostring` and `print`.
     ToString,
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
     /// The `__pairs` metamethod.
     ///
     /// This is not an operator, but it will be called by the built-in `pairs` function.
+    ///
+    /// Requires `feature = "lua54/lua53/lua52"`
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52", doc))]
     Pairs,
+    /// The `__close` metamethod.
+    ///
+    /// Executed when a variable, that marked as to-be-closed, goes out of scope.
+    ///
+    /// More information about to-be-closed variabled can be found in the Lua 5.4
+    /// [documentation][lua_doc].
+    ///
+    /// Requires `feature = "lua54"`
+    ///
+    /// [lua_doc]: https://www.lua.org/manual/5.4/manual.html#3.3.8
+    #[cfg(any(feature = "lua54", doc))]
+    Close,
 }
 
 impl MetaMethod {
@@ -92,20 +117,22 @@ impl MetaMethod {
             MetaMethod::Mod => b"__mod",
             MetaMethod::Pow => b"__pow",
             MetaMethod::Unm => b"__unm",
-            #[cfg(feature = "lua53")]
+
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
             MetaMethod::IDiv => b"__idiv",
-            #[cfg(feature = "lua53")]
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
             MetaMethod::BAnd => b"__band",
-            #[cfg(feature = "lua53")]
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
             MetaMethod::BOr => b"__bor",
-            #[cfg(feature = "lua53")]
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
             MetaMethod::BXor => b"__bxor",
-            #[cfg(feature = "lua53")]
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
             MetaMethod::BNot => b"__bnot",
-            #[cfg(feature = "lua53")]
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
             MetaMethod::Shl => b"__shl",
-            #[cfg(feature = "lua53")]
+            #[cfg(any(feature = "lua54", feature = "lua53"))]
             MetaMethod::Shr => b"__shr",
+
             MetaMethod::Concat => b"__concat",
             MetaMethod::Len => b"__len",
             MetaMethod::Eq => b"__eq",
@@ -115,8 +142,12 @@ impl MetaMethod {
             MetaMethod::NewIndex => b"__newindex",
             MetaMethod::Call => b"__call",
             MetaMethod::ToString => b"__tostring",
-            #[cfg(any(feature = "lua53", feature = "lua52"))]
+
+            #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
             MetaMethod::Pairs => b"__pairs",
+
+            #[cfg(feature = "lua54")]
+            MetaMethod::Close => b"__close",
         }
     }
 }
@@ -137,7 +168,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
         S: ?Sized + AsRef<[u8]>,
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        M: 'static + Fn(&'lua Lua, &T, A) -> Result<R>;
+        M: 'static + MaybeSend + Fn(&'lua Lua, &T, A) -> Result<R>;
 
     /// Add a regular method which accepts a `&mut T` as the first parameter.
     ///
@@ -149,23 +180,26 @@ pub trait UserDataMethods<'lua, T: UserData> {
         S: ?Sized + AsRef<[u8]>,
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        M: 'static + FnMut(&'lua Lua, &mut T, A) -> Result<R>;
+        M: 'static + MaybeSend + FnMut(&'lua Lua, &mut T, A) -> Result<R>;
 
     /// Add an async method which accepts a `T` as the first parameter and returns Future.
     /// The passed `T` is cloned from the original value.
     ///
     /// Refer to [`add_method`] for more information about the implementation.
     ///
+    /// Requires `feature = "async"`
+    ///
     /// [`add_method`]: #method.add_method
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     fn add_async_method<S, A, R, M, MR>(&mut self, name: &S, method: M)
     where
         T: Clone,
         S: ?Sized + AsRef<[u8]>,
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        M: 'static + Fn(&'lua Lua, T, A) -> MR,
-        MR: 'static + Future<Output = Result<R>>;
+        M: 'static + MaybeSend + Fn(&'lua Lua, T, A) -> MR,
+        MR: 'lua + Future<Output = Result<R>>;
 
     /// Add a regular method as a function which accepts generic arguments, the first argument will
     /// be a `UserData` of type T if the method is called with Lua method syntax:
@@ -181,7 +215,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
         S: ?Sized + AsRef<[u8]>,
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        F: 'static + Fn(&'lua Lua, A) -> Result<R>;
+        F: 'static + MaybeSend + Fn(&'lua Lua, A) -> Result<R>;
 
     /// Add a regular method as a mutable function which accepts generic arguments.
     ///
@@ -193,23 +227,26 @@ pub trait UserDataMethods<'lua, T: UserData> {
         S: ?Sized + AsRef<[u8]>,
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        F: 'static + FnMut(&'lua Lua, A) -> Result<R>;
+        F: 'static + MaybeSend + FnMut(&'lua Lua, A) -> Result<R>;
 
     /// Add a regular method as an async function which accepts generic arguments
     /// and returns Future.
     ///
     /// This is an async version of [`add_function`].
     ///
+    /// Requires `feature = "async"`
+    ///
     /// [`add_function`]: #method.add_function
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     fn add_async_function<S, A, R, F, FR>(&mut self, name: &S, function: F)
     where
         T: Clone,
         S: ?Sized + AsRef<[u8]>,
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        F: 'static + Fn(&'lua Lua, A) -> FR,
-        FR: 'static + Future<Output = Result<R>>;
+        F: 'static + MaybeSend + Fn(&'lua Lua, A) -> FR,
+        FR: 'lua + Future<Output = Result<R>>;
 
     /// Add a metamethod which accepts a `&T` as the first parameter.
     ///
@@ -223,7 +260,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
     where
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        M: 'static + Fn(&'lua Lua, &T, A) -> Result<R>;
+        M: 'static + MaybeSend + Fn(&'lua Lua, &T, A) -> Result<R>;
 
     /// Add a metamethod as a function which accepts a `&mut T` as the first parameter.
     ///
@@ -237,7 +274,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
     where
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        M: 'static + FnMut(&'lua Lua, &mut T, A) -> Result<R>;
+        M: 'static + MaybeSend + FnMut(&'lua Lua, &mut T, A) -> Result<R>;
 
     /// Add a metamethod which accepts generic arguments.
     ///
@@ -248,7 +285,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
     where
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        F: 'static + Fn(&'lua Lua, A) -> Result<R>;
+        F: 'static + MaybeSend + Fn(&'lua Lua, A) -> Result<R>;
 
     /// Add a metamethod as a mutable function which accepts generic arguments.
     ///
@@ -259,7 +296,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
     where
         A: FromLuaMulti<'lua>,
         R: ToLuaMulti<'lua>,
-        F: 'static + FnMut(&'lua Lua, A) -> Result<R>;
+        F: 'static + MaybeSend + FnMut(&'lua Lua, A) -> Result<R>;
 }
 
 /// Trait for custom userdata types.
@@ -331,6 +368,71 @@ pub trait UserData: Sized {
     fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(_methods: &mut M) {}
 }
 
+pub(crate) struct UserDataWrapped<T> {
+    pub(crate) data: *mut T,
+    #[cfg(feature = "serialize")]
+    ser: *mut dyn erased_serde::Serialize,
+}
+
+impl<T> Drop for UserDataWrapped<T> {
+    fn drop(&mut self) {
+        unsafe {
+            drop(Box::from_raw(self.data));
+            #[cfg(feature = "serialize")]
+            if self.data as *mut () != self.ser as *mut () {
+                drop(Box::from_raw(self.ser));
+            }
+        }
+    }
+}
+
+impl<T> UserDataWrapped<T> {
+    pub(crate) fn new(data: T) -> Self {
+        UserDataWrapped {
+            data: Box::into_raw(Box::new(data)),
+            #[cfg(feature = "serialize")]
+            ser: Box::into_raw(Box::new(UserDataSerializeError)),
+        }
+    }
+
+    #[cfg(feature = "serialize")]
+    pub(crate) fn new_ser(data: T) -> Self
+    where
+        T: 'static + Serialize,
+    {
+        let data_raw = Box::into_raw(Box::new(data));
+        UserDataWrapped {
+            data: data_raw,
+            ser: data_raw,
+        }
+    }
+}
+
+impl<T> AsRef<T> for UserDataWrapped<T> {
+    fn as_ref(&self) -> &T {
+        unsafe { &*self.data }
+    }
+}
+
+impl<T> AsMut<T> for UserDataWrapped<T> {
+    fn as_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.data }
+    }
+}
+
+#[cfg(feature = "serialize")]
+pub(crate) struct UserDataSerializeError;
+
+#[cfg(feature = "serialize")]
+impl Serialize for UserDataSerializeError {
+    fn serialize<S>(&self, _serializer: S) -> StdResult<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        Err(ser::Error::custom("cannot serialize <userdata>"))
+    }
+}
+
 /// Handle to an internal Lua userdata for any type that implements [`UserData`].
 ///
 /// Similar to `std::any::Any`, this provides an interface for dynamic type checking via the [`is`]
@@ -353,7 +455,7 @@ pub struct AnyUserData<'lua>(pub(crate) LuaRef<'lua>);
 impl<'lua> AnyUserData<'lua> {
     /// Checks whether the type of this userdata is `T`.
     pub fn is<T: 'static + UserData>(&self) -> bool {
-        match self.inspect(|_: &RefCell<T>| Ok(())) {
+        match self.inspect(|_: &UserDataCell<T>| Ok(())) {
             Ok(()) => true,
             Err(Error::UserDataTypeMismatch) => false,
             Err(_) => unreachable!(),
@@ -367,7 +469,10 @@ impl<'lua> AnyUserData<'lua> {
     /// Returns a `UserDataBorrowError` if the userdata is already mutably borrowed. Returns a
     /// `UserDataTypeMismatch` if the userdata is not of type `T`.
     pub fn borrow<T: 'static + UserData>(&self) -> Result<Ref<T>> {
-        self.inspect(|cell| Ok(cell.try_borrow().map_err(|_| Error::UserDataBorrowError)?))
+        self.inspect(|cell| {
+            let cell_ref = cell.try_borrow().map_err(|_| Error::UserDataBorrowError)?;
+            Ok(Ref::map(cell_ref, |x| unsafe { &*x.data }))
+        })
     }
 
     /// Borrow this userdata mutably if it is of type `T`.
@@ -378,27 +483,29 @@ impl<'lua> AnyUserData<'lua> {
     /// `UserDataTypeMismatch` if the userdata is not of type `T`.
     pub fn borrow_mut<T: 'static + UserData>(&self) -> Result<RefMut<T>> {
         self.inspect(|cell| {
-            Ok(cell
+            let cell_ref = cell
                 .try_borrow_mut()
-                .map_err(|_| Error::UserDataBorrowMutError)?)
+                .map_err(|_| Error::UserDataBorrowMutError)?;
+            Ok(RefMut::map(cell_ref, |x| unsafe { &mut *x.data }))
         })
     }
 
     /// Sets an associated value to this `AnyUserData`.
     ///
     /// The value may be any Lua value whatsoever, and can be retrieved with [`get_user_value`].
+    /// As Lua < 5.3 allows to store only tables, the value will be stored in a table at index 1.
     ///
     /// [`get_user_value`]: #method.get_user_value
     pub fn set_user_value<V: ToLua<'lua>>(&self, v: V) -> Result<()> {
         let lua = self.0.lua;
         #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
         let v = {
-            // Lua 5.2/5.1 allows to store only table. Then we will wrap the value.
+            // Lua 5.2/5.1 allows to store only a table. Then we will wrap the value.
             let t = lua.create_table()?;
             t.raw_set(1, v)?;
             crate::Value::Table(t)
         };
-        #[cfg(feature = "lua53")]
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         let v = v.to_lua(lua)?;
         unsafe {
             let _sg = StackGuard::new(lua.state);
@@ -412,6 +519,8 @@ impl<'lua> AnyUserData<'lua> {
 
     /// Returns an associated value set by [`set_user_value`].
     ///
+    /// For Lua < 5.3 the value will be automatically extracted from the table wrapper from index 1.
+    ///
     /// [`set_user_value`]: #method.set_user_value
     pub fn get_user_value<V: FromLua<'lua>>(&self) -> Result<V> {
         let lua = self.0.lua;
@@ -424,10 +533,26 @@ impl<'lua> AnyUserData<'lua> {
         };
         #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
         return crate::Table::from_lua(res, lua)?.get(1);
-        #[cfg(feature = "lua53")]
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         V::from_lua(res, lua)
     }
 
+    /// Checks for a metamethod in this `AnyUserData`
+    pub fn has_metamethod(&self, method: MetaMethod) -> Result<bool> {
+        match self.get_metatable() {
+            Ok(mt) => {
+                let name = self.0.lua.create_string(method.name())?;
+                if let Value::Nil = mt.raw_get(name)? {
+                    Ok(false)
+                } else {
+                    Ok(true)
+                }
+            }
+            Err(Error::UserDataTypeMismatch) => Ok(false),
+            Err(e) => Err(e),
+        }
+    }
+
     fn get_metatable(&self) -> Result<Table<'lua>> {
         unsafe {
             let lua = self.0.lua;
@@ -467,7 +592,7 @@ impl<'lua> AnyUserData<'lua> {
     fn inspect<'a, T, R, F>(&'a self, func: F) -> Result<R>
     where
         T: 'static + UserData,
-        F: FnOnce(&'a RefCell<T>) -> Result<R>,
+        F: FnOnce(&'a UserDataCell<T>) -> Result<R>,
     {
         unsafe {
             let lua = self.0.lua;
@@ -486,9 +611,16 @@ impl<'lua> AnyUserData<'lua> {
                 );
 
                 if ffi::lua_rawequal(lua.state, -1, -2) == 0 {
-                    Err(Error::UserDataTypeMismatch)
+                    // Maybe UserData destructed?
+                    ffi::lua_pop(lua.state, 1);
+                    get_destructed_userdata_metatable(lua.state);
+                    if ffi::lua_rawequal(lua.state, -1, -2) == 1 {
+                        Err(Error::UserDataDestructed)
+                    } else {
+                        Err(Error::UserDataTypeMismatch)
+                    }
                 } else {
-                    func(&*get_userdata::<RefCell<T>>(lua.state, -3))
+                    func(&*get_userdata::<UserDataCell<T>>(lua.state, -3))
                 }
             }
         }
@@ -507,3 +639,24 @@ impl<'lua> AsRef<AnyUserData<'lua>> for AnyUserData<'lua> {
         self
     }
 }
+
+#[cfg(feature = "serialize")]
+impl<'lua> Serialize for AnyUserData<'lua> {
+    fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let f = || unsafe {
+            let lua = self.0.lua;
+            let _sg = StackGuard::new(lua.state);
+            assert_stack(lua.state, 2);
+
+            lua.push_userdata_ref(&self.0)?;
+            let ud = &*get_userdata::<UserDataCell<()>>(lua.state, -1);
+            (*ud.try_borrow().map_err(|_| Error::UserDataBorrowError)?.ser)
+                .serialize(serializer)
+                .map_err(|err| Error::SerializeError(err.to_string()))
+        };
+        f().map_err(ser::Error::custom)
+    }
+}

src/util.rs

@@ -1,18 +1,18 @@
 use std::any::{Any, TypeId};
 use std::borrow::Cow;
-use std::cell::RefCell;
 use std::collections::HashMap;
 use std::fmt::Write;
 use std::os::raw::{c_char, c_int, c_void};
 use std::panic::{catch_unwind, resume_unwind, AssertUnwindSafe};
-use std::rc::Rc;
+use std::sync::{Arc, Mutex};
 use std::{mem, ptr, slice};
 
 use crate::error::{Error, Result};
 use crate::ffi;
 
-thread_local! {
-    static METATABLE_CACHE: RefCell<HashMap<TypeId, c_int>> = RefCell::new(HashMap::new());
+lazy_static::lazy_static! {
+    // The capacity must(!) be greater than number of stored keys
+    static ref METATABLE_CACHE: Mutex<HashMap<TypeId, u8>> = Mutex::new(HashMap::with_capacity(32));
 }
 
 // Checks that Lua has enough free stack space for future stack operations.  On failure, this will
@@ -57,10 +57,11 @@ impl Drop for StackGuard {
     fn drop(&mut self) {
         unsafe {
             let top = ffi::lua_gettop(self.state);
+            if top < self.top {
+                mlua_panic!("{} too many stack values popped", self.top - top)
+            }
             if top > self.top {
                 ffi::lua_settop(self.state, self.top);
-            } else if top < self.top {
-                mlua_panic!("{} too many stack values popped", self.top - top);
             }
         }
     }
@@ -185,7 +186,7 @@ pub unsafe fn pop_error(state: *mut ffi::lua_State, err_code: c_int) -> Error {
         if let Some(p) = (*panic).0.take() {
             resume_unwind(p);
         } else {
-            mlua_panic!("error during panic handling, panic was resumed twice")
+            Error::PreviouslyResumedPanic
         }
     } else {
         let err_string = to_string(state, -1).into_owned();
@@ -278,15 +279,11 @@ pub unsafe fn push_meta_gc_userdata<MT: Any, T>(state: *mut ffi::lua_State, t: T
 
 // Uses 2 stack spaces, does not call checkstack
 pub unsafe fn get_gc_userdata<T: Any>(state: *mut ffi::lua_State, index: c_int) -> *mut T {
-    get_meta_gc_userdata::<T, T>(state, index)
-}
-
-pub unsafe fn get_meta_gc_userdata<MT: Any, T>(state: *mut ffi::lua_State, index: c_int) -> *mut T {
     let ud = ffi::lua_touserdata(state, index) as *mut T;
     if ud.is_null() || ffi::lua_getmetatable(state, index) == 0 {
         return ptr::null_mut();
     }
-    get_gc_metatable_for::<MT>(state);
+    get_gc_metatable_for::<T>(state);
     let res = ffi::lua_rawequal(state, -1, -2) != 0;
     ffi::lua_pop(state, 2);
     if !res {
@@ -468,32 +465,41 @@ pub unsafe extern "C" fn error_traceback(state: *mut ffi::lua_State) -> c_int {
             ud,
             WrappedError(Error::CallbackError {
                 traceback,
-                cause: Rc::new(error),
+                cause: Arc::new(error),
             }),
         );
         get_gc_metatable_for::<WrappedError>(state);
         ffi::lua_setmetatable(state, -2);
-    } else if let None = get_gc_userdata::<WrappedPanic>(state, -1).as_ref() {
-        if ffi::lua_checkstack(state, LUA_TRACEBACK_STACK) != 0 {
-            let s = ffi::luaL_tolstring(state, -1, ptr::null_mut());
-            ffi::luaL_traceback(state, state, s, 0);
-            ffi::lua_remove(state, -2);
-        }
+    } else if get_gc_userdata::<WrappedPanic>(state, -1).is_null()
+        && ffi::lua_checkstack(state, LUA_TRACEBACK_STACK) != 0
+    {
+        let s = ffi::luaL_tolstring(state, -1, ptr::null_mut());
+        ffi::luaL_traceback(state, state, s, 0);
+        ffi::lua_remove(state, -2);
     }
     1
 }
 
 // Does not call lua_checkstack, uses 1 stack space.
-pub unsafe fn get_main_state(state: *mut ffi::lua_State) -> *mut ffi::lua_State {
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+pub unsafe fn get_main_state(state: *mut ffi::lua_State) -> Option<*mut ffi::lua_State> {
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     {
         ffi::lua_rawgeti(state, ffi::LUA_REGISTRYINDEX, ffi::LUA_RIDX_MAINTHREAD);
         let main_state = ffi::lua_tothread(state, -1);
         ffi::lua_pop(state, 1);
-        main_state
+        Some(main_state)
     }
     #[cfg(any(feature = "lua51", feature = "luajit"))]
-    state
+    {
+        // Check the current state first
+        let is_main_state = ffi::lua_pushthread(state) == 1;
+        ffi::lua_pop(state, 1);
+        if is_main_state {
+            Some(state)
+        } else {
+            None
+        }
+    }
 }
 
 // Pushes a WrappedError to the top of the stack.  Uses two stack spaces and does not call
@@ -519,6 +525,16 @@ pub unsafe fn init_gc_metatable_for<T: Any>(
 ) {
     let type_id = TypeId::of::<T>();
 
+    let ref_addr = {
+        let mut mt_cache = mlua_expect!(METATABLE_CACHE.lock(), "cannot lock metatable cache");
+        mlua_assert!(
+            mt_cache.capacity() - mt_cache.len() > 0,
+            "out of metatable cache capacity"
+        );
+        mt_cache.insert(type_id, 0);
+        &mt_cache[&type_id] as *const u8
+    };
+
     ffi::lua_newtable(state);
 
     ffi::lua_pushstring(state, cstr!("__gc"));
@@ -533,15 +549,16 @@ pub unsafe fn init_gc_metatable_for<T: Any>(
         f(state)
     }
 
-    let ref_addr = ffi::luaL_ref(state, ffi::LUA_REGISTRYINDEX);
-    METATABLE_CACHE.with(|mc| mc.borrow_mut().insert(type_id, ref_addr));
+    ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, ref_addr as *mut c_void);
 }
 
 pub unsafe fn get_gc_metatable_for<T: Any>(state: *mut ffi::lua_State) {
     let type_id = TypeId::of::<T>();
-    let ref_addr = METATABLE_CACHE
-        .with(|mc| *mlua_expect!(mc.borrow().get(&type_id), "gc metatable does not exist"));
-    ffi::lua_rawgeti(state, ffi::LUA_REGISTRYINDEX, ref_addr as ffi::lua_Integer);
+    let ref_addr = {
+        let mt_cache = mlua_expect!(METATABLE_CACHE.lock(), "cannot lock metatable cache");
+        mlua_expect!(mt_cache.get(&type_id), "gc metatable does not exist") as *const u8
+    };
+    ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, ref_addr as *mut c_void);
 }
 
 // Initialize the error, panic, and destructed userdata metatables.
@@ -570,27 +587,22 @@ pub unsafe fn init_error_registry(state: *mut ffi::lua_State) {
                 Ok(err_buf)
             } else if let Some(panic) = get_gc_userdata::<WrappedPanic>(state, -1).as_ref() {
                 if let Some(ref p) = (*panic).0 {
-                    ffi::lua_pushlightuserdata(
-                        state,
-                        &ERROR_PRINT_BUFFER_KEY as *const u8 as *mut c_void,
-                    );
-                    ffi::lua_rawget(state, ffi::LUA_REGISTRYINDEX);
+                    let err_buf_key = &ERROR_PRINT_BUFFER_KEY as *const u8 as *const c_void;
+                    ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, err_buf_key);
                     let err_buf = ffi::lua_touserdata(state, -1) as *mut String;
+                    (*err_buf).clear();
                     ffi::lua_pop(state, 2);
 
-                    let error = if let Some(x) = p.downcast_ref::<&str>() {
-                        x.to_string()
-                    } else if let Some(x) = p.downcast_ref::<String>() {
-                        x.to_string()
+                    if let Some(msg) = p.downcast_ref::<&str>() {
+                        let _ = write!(&mut (*err_buf), "{}", msg);
+                    } else if let Some(msg) = p.downcast_ref::<String>() {
+                        let _ = write!(&mut (*err_buf), "{}", msg);
                     } else {
-                        "panic".to_string()
+                        let _ = write!(&mut (*err_buf), "<panic>");
                     };
-
-                    (*err_buf).clear();
-                    let _ = write!(&mut (*err_buf), "{}", error);
                     Ok(err_buf)
                 } else {
-                    mlua_panic!("error during panic handling, panic was resumed")
+                    Err(Error::PreviouslyResumedPanic)
                 }
             } else {
                 // I'm not sure whether this is possible to trigger without bugs in mlua?
@@ -650,12 +662,19 @@ pub unsafe fn init_error_registry(state: *mut ffi::lua_State) {
         cstr!("__mod"),
         cstr!("__pow"),
         cstr!("__unm"),
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         cstr!("__idiv"),
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         cstr!("__band"),
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         cstr!("__bor"),
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         cstr!("__bxor"),
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         cstr!("__bnot"),
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         cstr!("__shl"),
+        #[cfg(any(feature = "lua54", feature = "lua53"))]
         cstr!("__shr"),
         cstr!("__concat"),
         cstr!("__len"),
@@ -666,8 +685,12 @@ pub unsafe fn init_error_registry(state: *mut ffi::lua_State) {
         cstr!("__newindex"),
         cstr!("__call"),
         cstr!("__tostring"),
+        #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
         cstr!("__pairs"),
+        #[cfg(any(feature = "lua53", feature = "lua52"))]
         cstr!("__ipairs"),
+        #[cfg(feature = "lua54")]
+        cstr!("__close"),
     ] {
         ffi::lua_pushstring(state, method);
         ffi::lua_pushcfunction(state, destructed_error);
@@ -693,7 +716,7 @@ pub unsafe fn init_error_registry(state: *mut ffi::lua_State) {
 }
 
 struct WrappedError(pub Error);
-struct WrappedPanic(pub Option<Box<dyn Any + Send + 'static>>);
+pub(crate) struct WrappedPanic(pub Option<Box<dyn Any + Send + 'static>>);
 
 // Converts the given lua value to a string in a reasonable format without causing a Lua error or
 // panicking.
@@ -727,7 +750,7 @@ unsafe fn to_string<'a>(state: *mut ffi::lua_State, index: c_int) -> Cow<'a, str
     }
 }
 
-unsafe fn get_destructed_userdata_metatable(state: *mut ffi::lua_State) {
+pub(crate) unsafe fn get_destructed_userdata_metatable(state: *mut ffi::lua_State) {
     ffi::lua_pushlightuserdata(
         state,
         &DESTRUCTED_USERDATA_METATABLE as *const u8 as *mut c_void,

src/value.rs

@@ -1,6 +1,12 @@
 use std::iter::{self, FromIterator};
 use std::{slice, str, vec};
 
+#[cfg(feature = "serialize")]
+use {
+    serde::ser::{self, Serialize, Serializer},
+    std::result::Result as StdResult,
+};
+
 use crate::error::{Error, Result};
 use crate::ffi;
 use crate::function::Function;
@@ -110,6 +116,31 @@ impl<'lua> AsRef<Value<'lua>> for Value<'lua> {
     }
 }
 
+#[cfg(feature = "serialize")]
+impl<'lua> Serialize for Value<'lua> {
+    fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self {
+            Value::Nil => serializer.serialize_unit(),
+            Value::Boolean(b) => serializer.serialize_bool(*b),
+            #[allow(clippy::useless_conversion)]
+            Value::Integer(i) => serializer.serialize_i64((*i).into()),
+            #[allow(clippy::useless_conversion)]
+            Value::Number(n) => serializer.serialize_f64((*n).into()),
+            Value::String(s) => s.serialize(serializer),
+            Value::Table(t) => t.serialize(serializer),
+            Value::UserData(ud) => ud.serialize(serializer),
+            Value::LightUserData(ud) if ud.0.is_null() => serializer.serialize_none(),
+            Value::Error(_) | Value::LightUserData(_) | Value::Function(_) | Value::Thread(_) => {
+                let msg = format!("cannot serialize <{}>", self.type_name());
+                Err(ser::Error::custom(msg))
+            }
+        }
+    }
+}
+
 /// Trait for types convertible to `Value`.
 pub trait ToLua<'lua> {
     /// Performs the conversion.
@@ -159,7 +190,7 @@ impl<'a, 'lua> IntoIterator for &'a MultiValue<'lua> {
     type IntoIter = iter::Rev<slice::Iter<'a, Value<'lua>>>;
 
     fn into_iter(self) -> Self::IntoIter {
-        (&self.0).into_iter().rev()
+        (&self.0).iter().rev()
     }
 }
 

tests/async.rs

@@ -2,12 +2,18 @@
 
 use std::cell::Cell;
 use std::rc::Rc;
+use std::sync::{
+    atomic::{AtomicI64, Ordering},
+    Arc,
+};
 use std::time::Duration;
 
 use futures_timer::Delay;
 use futures_util::stream::TryStreamExt;
 
-use mlua::{Error, Function, Lua, Result, Table, TableExt, UserData, UserDataMethods};
+use mlua::{
+    Error, Function, Lua, Result, Table, TableExt, Thread, UserData, UserDataMethods, Value,
+};
 
 #[tokio::test]
 async fn test_async_function() -> Result<()> {
@@ -119,6 +125,24 @@ async fn test_async_handle_yield() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn test_async_multi_return_nil() -> Result<()> {
+    let lua = Lua::new();
+    lua.globals().set(
+        "func",
+        lua.create_async_function(|_, _: ()| async { Ok((Option::<String>::None, "error")) })?,
+    )?;
+
+    lua.load(
+        r#"
+        local ok, err = func()
+        assert(err == "error")
+    "#,
+    )
+    .exec_async()
+    .await
+}
+
 #[tokio::test]
 async fn test_async_return_async_closure() -> Result<()> {
     let lua = Lua::new();
@@ -180,7 +204,7 @@ async fn test_async_thread_stream() -> Result<()> {
 async fn test_async_thread() -> Result<()> {
     let lua = Lua::new();
 
-    let cnt = Rc::new(10); // sleep 10ms
+    let cnt = Arc::new(10); // sleep 10ms
     let cnt2 = cnt.clone();
     let f = lua.create_async_function(move |_lua, ()| {
         let cnt3 = cnt2.clone();
@@ -194,9 +218,9 @@ async fn test_async_thread() -> Result<()> {
 
     assert_eq!(res, "done");
 
-    assert_eq!(Rc::strong_count(&cnt), 2);
+    assert_eq!(Arc::strong_count(&cnt), 2);
     lua.gc_collect()?; // thread_s is non-resumable and subject to garbage collection
-    assert_eq!(Rc::strong_count(&cnt), 1);
+    assert_eq!(Arc::strong_count(&cnt), 1);
 
     Ok(())
 }
@@ -252,18 +276,18 @@ async fn test_async_table() -> Result<()> {
 #[tokio::test]
 async fn test_async_userdata() -> Result<()> {
     #[derive(Clone)]
-    struct MyUserData(Rc<Cell<i64>>);
+    struct MyUserData(Arc<AtomicI64>);
 
     impl UserData for MyUserData {
         fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
             methods.add_async_method("get_value", |_, data, ()| async move {
                 Delay::new(Duration::from_millis(10)).await;
-                Ok(data.0.get())
+                Ok(data.0.load(Ordering::Relaxed))
             });
 
             methods.add_async_method("set_value", |_, data, n| async move {
                 Delay::new(Duration::from_millis(10)).await;
-                data.0.set(n);
+                data.0.store(n, Ordering::Relaxed);
                 Ok(())
             });
 
@@ -277,15 +301,15 @@ async fn test_async_userdata() -> Result<()> {
     let lua = Lua::new();
     let globals = lua.globals();
 
-    let userdata = lua.create_userdata(MyUserData(Rc::new(Cell::new(11))))?;
+    let userdata = lua.create_userdata(MyUserData(Arc::new(AtomicI64::new(11))))?;
     globals.set("userdata", userdata.clone())?;
 
     lua.load(
         r#"
         assert(userdata:get_value() == 11)
         userdata:set_value(12)
-        assert(userdata:get_value() == 12)
         assert(userdata.sleep(5) == "elapsed:5ms")
+        assert(userdata:get_value() == 12)
     "#,
     )
     .exec_async()
@@ -293,3 +317,121 @@ async fn test_async_userdata() -> Result<()> {
 
     Ok(())
 }
+
+#[tokio::test]
+async fn test_async_scope() -> Result<()> {
+    let ref lua = Lua::new();
+
+    let ref rc = Rc::new(Cell::new(0));
+
+    let fut = lua.async_scope(|scope| async move {
+        let f = scope.create_async_function(move |_, n: u64| {
+            let rc2 = rc.clone();
+            async move {
+                rc2.set(42);
+                Delay::new(Duration::from_millis(n)).await;
+                assert_eq!(Rc::strong_count(&rc2), 2);
+                Ok(())
+            }
+        })?;
+
+        lua.globals().set("f", f.clone())?;
+
+        assert_eq!(Rc::strong_count(rc), 1);
+        let _ = f.call_async::<u64, ()>(10).await?;
+        assert_eq!(Rc::strong_count(rc), 1);
+
+        // Create future in partialy polled state (Poll::Pending)
+        let g = lua.create_thread(f)?;
+        g.resume::<u64, ()>(10)?;
+        lua.globals().set("g", g)?;
+        assert_eq!(Rc::strong_count(rc), 2);
+
+        Ok(())
+    });
+
+    assert_eq!(Rc::strong_count(rc), 1);
+    let _ = fut.await?;
+    assert_eq!(Rc::strong_count(rc), 1);
+
+    match lua
+        .globals()
+        .get::<_, Function>("f")?
+        .call_async::<_, ()>(10)
+        .await
+    {
+        Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+            Error::CallbackDestructed => {}
+            e => panic!("expected `CallbackDestructed` error cause, got {:?}", e),
+        },
+        r => panic!("improper return for destructed function: {:?}", r),
+    };
+
+    match lua.globals().get::<_, Thread>("g")?.resume::<_, Value>(()) {
+        Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+            Error::CallbackDestructed => {}
+            e => panic!("expected `CallbackDestructed` error cause, got {:?}", e),
+        },
+        r => panic!("improper return for destructed function: {:?}", r),
+    };
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn test_async_scope_userdata() -> Result<()> {
+    #[derive(Clone)]
+    struct MyUserData(Arc<AtomicI64>);
+
+    impl UserData for MyUserData {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_async_method("get_value", |_, data, ()| async move {
+                Delay::new(Duration::from_millis(10)).await;
+                Ok(data.0.load(Ordering::Relaxed))
+            });
+
+            methods.add_async_method("set_value", |_, data, n| async move {
+                Delay::new(Duration::from_millis(10)).await;
+                data.0.store(n, Ordering::Relaxed);
+                Ok(())
+            });
+
+            methods.add_async_function("sleep", |_, n| async move {
+                Delay::new(Duration::from_millis(n)).await;
+                Ok(format!("elapsed:{}ms", n))
+            });
+        }
+    }
+
+    let ref lua = Lua::new();
+
+    let ref arc = Arc::new(AtomicI64::new(11));
+
+    lua.async_scope(|scope| async move {
+        let ud = scope.create_userdata(MyUserData(arc.clone()))?;
+        lua.globals().set("userdata", ud)?;
+        lua.load(
+            r#"
+            assert(userdata:get_value() == 11)
+            userdata:set_value(12)
+            assert(userdata.sleep(5) == "elapsed:5ms")
+            assert(userdata:get_value() == 12)
+        "#,
+        )
+        .exec_async()
+        .await
+    })
+    .await?;
+
+    assert_eq!(Arc::strong_count(arc), 1);
+
+    match lua.load("userdata:get_value()").exec_async().await {
+        Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+            Error::CallbackDestructed => {}
+            e => panic!("expected `CallbackDestructed` error cause, got {:?}", e),
+        },
+        r => panic!("improper return for destructed userdata: {:?}", r),
+    };
+
+    Ok(())
+}

tests/compile.rs

@@ -0,0 +1,24 @@
+#[test]
+#[ignore]
+fn test_compilation() {
+    let t = trybuild::TestCases::new();
+
+    t.compile_fail("tests/compile/function_borrow.rs");
+    t.compile_fail("tests/compile/lua_norefunwindsafe.rs");
+    t.compile_fail("tests/compile/ref_nounwindsafe.rs");
+    t.compile_fail("tests/compile/scope_callback_capture.rs");
+    t.compile_fail("tests/compile/scope_callback_inner.rs");
+    t.compile_fail("tests/compile/scope_callback_outer.rs");
+    t.compile_fail("tests/compile/scope_invariance.rs");
+    t.compile_fail("tests/compile/scope_mutable_aliasing.rs");
+    t.compile_fail("tests/compile/scope_userdata_borrow.rs");
+    t.compile_fail("tests/compile/static_callback_args.rs");
+
+    #[cfg(feature = "async")]
+    t.compile_fail("tests/compile/async_nonstatic_userdata.rs");
+
+    #[cfg(feature = "send")]
+    t.compile_fail("tests/compile/non_send.rs");
+    #[cfg(not(feature = "send"))]
+    t.pass("tests/compile/non_send.rs");
+}

tests/compile/async_nonstatic_userdata.rs

@@ -0,0 +1,17 @@
+use mlua::{Lua, UserData, UserDataMethods};
+
+fn main() {
+    let ref lua = Lua::new();
+
+    #[derive(Clone)]
+    struct MyUserData<'a>(&'a i64);
+
+    impl<'a> UserData for MyUserData<'a> {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_async_method("print", |_, data, ()| async move {
+                println!("{}", data.0);
+                Ok(())
+            });
+        }
+    }
+}

tests/compile/async_nonstatic_userdata.stderr

@@ -0,0 +1,36 @@
+error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
+  --> $DIR/async_nonstatic_userdata.rs:11:72
+   |
+11 |               methods.add_async_method("print", |_, data, ()| async move {
+   |  ________________________________________________________________________^
+12 | |                 println!("{}", data.0);
+13 | |                 Ok(())
+14 | |             });
+   | |_____________^
+   |
+note: first, the lifetime cannot outlive the lifetime `'a` as defined on the impl at 9:10...
+  --> $DIR/async_nonstatic_userdata.rs:9:10
+   |
+9  |     impl<'a> UserData for MyUserData<'a> {
+   |          ^^
+note: ...so that the types are compatible
+  --> $DIR/async_nonstatic_userdata.rs:11:72
+   |
+11 |               methods.add_async_method("print", |_, data, ()| async move {
+   |  ________________________________________________________________________^
+12 | |                 println!("{}", data.0);
+13 | |                 Ok(())
+14 | |             });
+   | |_____________^
+   = note: expected `(MyUserData<'_>,)`
+              found `(MyUserData<'a>,)`
+note: but, the lifetime must be valid for the lifetime `'lua` as defined on the method body at 10:24...
+  --> $DIR/async_nonstatic_userdata.rs:10:24
+   |
+10 |         fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+   |                        ^^^^
+note: ...so that the type `impl Future` will meet its required lifetime bounds
+  --> $DIR/async_nonstatic_userdata.rs:11:21
+   |
+11 |             methods.add_async_method("print", |_, data, ()| async move {
+   |                     ^^^^^^^^^^^^^^^^

tests/compile/lua_norefunwindsafe.stderr

@@ -0,0 +1,16 @@
+error[E0277]: the type `UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+   --> $DIR/lua_norefunwindsafe.rs:7:5
+    |
+7   |     catch_unwind(|| lua.create_table().unwrap());
+    |     ^^^^^^^^^^^^ `UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+    |
+   ::: $RUST/std/src/panic.rs
+    |
+    | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+    |                                        ---------- required by this bound in `catch_unwind`
+    |
+    = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<()>`
+    = note: required because it appears within the type `PhantomData<UnsafeCell<()>>`
+    = note: required because it appears within the type `Lua`
+    = note: required because of the requirements on the impl of `UnwindSafe` for `&Lua`
+    = note: required because it appears within the type `[closure@$DIR/tests/compile/lua_norefunwindsafe.rs:7:18: 7:48]`

tests/compile/non_send.rs

@@ -0,0 +1,17 @@
+use std::cell::Cell;
+use std::rc::Rc;
+
+use mlua::{Lua, Result};
+
+fn main() -> Result<()> {
+    let lua = Lua::new();
+
+    let data = Rc::new(Cell::new(0));
+
+    lua.create_function(move |_, ()| {
+        Ok(data.get())
+    })?
+    .call::<_, i32>(())?;
+
+    Ok(())
+}

tests/compile/non_send.stderr

@@ -0,0 +1,14 @@
+error[E0277]: `Rc<Cell<i32>>` cannot be sent between threads safely
+  --> $DIR/non_send.rs:11:9
+   |
+11 |       lua.create_function(move |_, ()| {
+   |  _________^^^^^^^^^^^^^^^_-
+   | |         |
+   | |         `Rc<Cell<i32>>` cannot be sent between threads safely
+12 | |         Ok(data.get())
+13 | |     })?
+   | |_____- within this `[closure@$DIR/tests/compile/non_send.rs:11:25: 13:6]`
+   |
+   = help: within `[closure@$DIR/tests/compile/non_send.rs:11:25: 13:6]`, the trait `Send` is not implemented for `Rc<Cell<i32>>`
+   = note: required because it appears within the type `[closure@$DIR/tests/compile/non_send.rs:11:25: 13:6]`
+   = note: required because of the requirements on the impl of `mlua::types::MaybeSend` for `[closure@$DIR/tests/compile/non_send.rs:11:25: 13:6]`

tests/compile/ref_nounwindsafe.stderr

@@ -0,0 +1,18 @@
+error[E0277]: the type `UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+   --> $DIR/ref_nounwindsafe.rs:8:5
+    |
+8   |     catch_unwind(move || table.set("a", "b").unwrap());
+    |     ^^^^^^^^^^^^ `UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+    |
+   ::: $RUST/std/src/panic.rs
+    |
+    | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+    |                                        ---------- required by this bound in `catch_unwind`
+    |
+    = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<()>`
+    = note: required because it appears within the type `PhantomData<UnsafeCell<()>>`
+    = note: required because it appears within the type `Lua`
+    = note: required because of the requirements on the impl of `UnwindSafe` for `&Lua`
+    = note: required because it appears within the type `mlua::types::LuaRef<'_>`
+    = note: required because it appears within the type `LuaTable<'_>`
+    = note: required because it appears within the type `[closure@$DIR/tests/compile/ref_nounwindsafe.rs:8:18: 8:54]`

tests/compile/scope_callback_capture.rs

@@ -0,0 +1,18 @@
+use mlua::{Lua, Table};
+
+fn main() {
+    let lua = Lua::new();
+    lua.scope(|scope| {
+        let mut inner: Option<Table> = None;
+        let f = scope
+            .create_function_mut(move |_, t: Table| {
+                if let Some(old) = inner.take() {
+                    // Access old callback `Lua`.
+                }
+                inner = Some(t);
+                Ok(())
+            })?;
+        f.call::<_, ()>(lua.create_table()?)?;
+        Ok(())
+    });
+}

tests/compile/scope_callback_capture.stderr

@@ -0,0 +1,26 @@
+warning: unused variable: `old`
+ --> $DIR/scope_callback_capture.rs:9:29
+  |
+9 |                 if let Some(old) = inner.take() {
+  |                             ^^^ help: if this is intentional, prefix it with an underscore: `_old`
+  |
+  = note: `#[warn(unused_variables)]` on by default
+
+error[E0521]: borrowed data escapes outside of closure
+  --> $DIR/scope_callback_capture.rs:7:17
+   |
+5  |       lua.scope(|scope| {
+   |                  -----
+   |                  |
+   |                  `scope` declared here, outside of the closure body
+   |                  `scope` is a reference that is only valid in the closure body
+6  |           let mut inner: Option<Table> = None;
+7  |           let f = scope
+   |  _________________^
+8  | |             .create_function_mut(move |_, t: Table| {
+9  | |                 if let Some(old) = inner.take() {
+10 | |                     // Access old callback `Lua`.
+...  |
+13 | |                 Ok(())
+14 | |             })?;
+   | |______________^ `scope` escapes the closure body here

tests/compile/scope_callback_inner.rs

@@ -0,0 +1,15 @@
+use mlua::{Lua, Table};
+
+fn main() {
+    let lua = Lua::new();
+    lua.scope(|scope| {
+        let mut inner: Option<Table> = None;
+        let f = scope
+            .create_function_mut(|_, t: Table| {
+                inner = Some(t);
+                Ok(())
+            })?;
+        f.call::<_, ()>(lua.create_table()?)?;
+        Ok(())
+    });
+}

tests/compile/scope_callback_inner.stderr

@@ -0,0 +1,42 @@
+error[E0521]: borrowed data escapes outside of closure
+  --> $DIR/scope_callback_inner.rs:7:17
+   |
+5  |       lua.scope(|scope| {
+   |                  -----
+   |                  |
+   |                  `scope` declared here, outside of the closure body
+   |                  `scope` is a reference that is only valid in the closure body
+6  |           let mut inner: Option<Table> = None;
+7  |           let f = scope
+   |  _________________^
+8  | |             .create_function_mut(|_, t: Table| {
+9  | |                 inner = Some(t);
+10 | |                 Ok(())
+11 | |             })?;
+   | |______________^ `scope` escapes the closure body here
+
+error[E0373]: closure may outlive the current function, but it borrows `inner`, which is owned by the current function
+  --> $DIR/scope_callback_inner.rs:8:34
+   |
+5  |     lua.scope(|scope| {
+   |                ----- has type `&Scope<'_, '2>`
+...
+8  |             .create_function_mut(|_, t: Table| {
+   |                                  ^^^^^^^^^^^^^ may outlive borrowed value `inner`
+9  |                 inner = Some(t);
+   |                 ----- `inner` is borrowed here
+   |
+note: function requires argument type to outlive `'2`
+  --> $DIR/scope_callback_inner.rs:7:17
+   |
+7  |           let f = scope
+   |  _________________^
+8  | |             .create_function_mut(|_, t: Table| {
+9  | |                 inner = Some(t);
+10 | |                 Ok(())
+11 | |             })?;
+   | |______________^
+help: to force the closure to take ownership of `inner` (and any other referenced variables), use the `move` keyword
+   |
+8  |             .create_function_mut(move |_, t: Table| {
+   |                                  ^^^^^^^^^^^^^^^^^^

tests/compile/scope_callback_outer.rs

@@ -0,0 +1,15 @@
+use mlua::{Lua, Table};
+
+fn main() {
+    let lua = Lua::new();
+    let mut outer: Option<Table> = None;
+    lua.scope(|scope| {
+        let f = scope
+            .create_function_mut(|_, t: Table| {
+                outer = Some(t);
+                Ok(())
+            })?;
+        f.call::<_, ()>(lua.create_table()?)?;
+        Ok(())
+    });
+}

tests/compile/scope_callback_outer.stderr

@@ -0,0 +1,30 @@
+error[E0521]: borrowed data escapes outside of closure
+  --> $DIR/scope_callback_outer.rs:7:17
+   |
+6  |       lua.scope(|scope| {
+   |                  -----
+   |                  |
+   |                  `scope` declared here, outside of the closure body
+   |                  `scope` is a reference that is only valid in the closure body
+7  |           let f = scope
+   |  _________________^
+8  | |             .create_function_mut(|_, t: Table| {
+9  | |                 outer = Some(t);
+10 | |                 Ok(())
+11 | |             })?;
+   | |______________^ `scope` escapes the closure body here
+
+error[E0597]: `outer` does not live long enough
+  --> $DIR/scope_callback_outer.rs:9:17
+   |
+6  |     lua.scope(|scope| {
+   |               ------- value captured here
+...
+9  |                 outer = Some(t);
+   |                 ^^^^^ borrowed value does not live long enough
+...
+15 | }
+   | -
+   | |
+   | `outer` dropped here while still borrowed
+   | borrow might be used here, when `outer` is dropped and runs the destructor for type `Option<LuaTable<'_>>`

tests/compile/scope_invariance.rs

@@ -0,0 +1,23 @@
+use mlua::Lua;
+
+struct Test {
+    field: i32,
+}
+
+fn main() {
+    let lua = Lua::new();
+    lua.scope(|scope| {
+        let f = {
+            let mut test = Test { field: 0 };
+
+            scope
+                .create_function_mut(|_, ()| {
+                    test.field = 42;
+                    //~^ error: `test` does not live long enough
+                    Ok(())
+                })?
+        };
+
+        f.call::<_, ()>(())
+    });
+}

tests/compile/scope_invariance.stderr

@@ -0,0 +1,25 @@
+error[E0373]: closure may outlive the current function, but it borrows `test`, which is owned by the current function
+  --> $DIR/scope_invariance.rs:14:38
+   |
+9  |     lua.scope(|scope| {
+   |                ----- has type `&Scope<'_, '1>`
+...
+14 |                 .create_function_mut(|_, ()| {
+   |                                      ^^^^^^^ may outlive borrowed value `test`
+15 |                     test.field = 42;
+   |                     ---- `test` is borrowed here
+   |
+note: function requires argument type to outlive `'1`
+  --> $DIR/scope_invariance.rs:13:13
+   |
+13 | /             scope
+14 | |                 .create_function_mut(|_, ()| {
+15 | |                     test.field = 42;
+16 | |                     //~^ error: `test` does not live long enough
+17 | |                     Ok(())
+18 | |                 })?
+   | |__________________^
+help: to force the closure to take ownership of `test` (and any other referenced variables), use the `move` keyword
+   |
+14 |                 .create_function_mut(move |_, ()| {
+   |                                      ^^^^^^^^^^^^

tests/compile/scope_mutable_aliasing.rs

@@ -0,0 +1,15 @@
+use mlua::{Lua, UserData};
+
+fn main() {
+    struct MyUserData<'a>(&'a mut i32);
+    impl<'a> UserData for MyUserData<'a> {};
+
+    let mut i = 1;
+
+    let lua = Lua::new();
+    lua.scope(|scope| {
+        let _a = scope.create_nonstatic_userdata(MyUserData(&mut i)).unwrap();
+        let _b = scope.create_nonstatic_userdata(MyUserData(&mut i)).unwrap();
+        Ok(())
+    });
+}

tests/compile/scope_mutable_aliasing.stderr

@@ -0,0 +1,9 @@
+error[E0499]: cannot borrow `i` as mutable more than once at a time
+  --> $DIR/scope_mutable_aliasing.rs:12:61
+   |
+11 |         let _a = scope.create_nonstatic_userdata(MyUserData(&mut i)).unwrap();
+   |                                                             ------ first mutable borrow occurs here
+12 |         let _b = scope.create_nonstatic_userdata(MyUserData(&mut i)).unwrap();
+   |                        -------------------------            ^^^^^^ second mutable borrow occurs here
+   |                        |
+   |                        first borrow later used by call

tests/compile/scope_userdata_borrow.rs

@@ -0,0 +1,19 @@
+use mlua::{Lua, UserData};
+
+fn main() {
+    // Should not allow userdata borrow to outlive lifetime of AnyUserData handle
+    struct MyUserData<'a>(&'a i32);
+    impl<'a> UserData for MyUserData<'a> {};
+
+    let igood = 1;
+
+    let lua = Lua::new();
+    lua.scope(|scope| {
+        let _ugood = scope.create_nonstatic_userdata(MyUserData(&igood)).unwrap();
+        let _ubad = {
+            let ibad = 42;
+            scope.create_nonstatic_userdata(MyUserData(&ibad)).unwrap();
+        };
+        Ok(())
+    });
+}

tests/compile/scope_userdata_borrow.stderr

@@ -0,0 +1,13 @@
+error[E0597]: `ibad` does not live long enough
+  --> $DIR/scope_userdata_borrow.rs:15:56
+   |
+11 |     lua.scope(|scope| {
+   |                ----- has type `&Scope<'_, '1>`
+...
+15 |             scope.create_nonstatic_userdata(MyUserData(&ibad)).unwrap();
+   |             -------------------------------------------^^^^^--
+   |             |                                          |
+   |             |                                          borrowed value does not live long enough
+   |             argument requires that `ibad` is borrowed for `'1`
+16 |         };
+   |         - `ibad` dropped here while still borrowed

tests/compile/static_callback_args.rs

@@ -0,0 +1,32 @@
+use std::cell::RefCell;
+
+use mlua::{Lua, Result, Table};
+
+fn main() -> Result<()> {
+    thread_local! {
+        static BAD_TIME: RefCell<Option<Table<'static>>> = RefCell::new(None);
+    }
+
+    let lua = Lua::new();
+
+    lua.create_function(|_, table: Table| {
+        BAD_TIME.with(|bt| {
+            *bt.borrow_mut() = Some(table);
+        });
+        Ok(())
+    })?
+    .call::<_, ()>(lua.create_table()?)?;
+
+    // In debug, this will panic with a reference leak before getting to the next part but
+    // it segfaults anyway.
+    drop(lua);
+
+    BAD_TIME.with(|bt| {
+        println!(
+            "you're gonna have a bad time: {}",
+            bt.borrow().as_ref().unwrap().len().unwrap()
+        );
+    });
+
+    Ok(())
+}

tests/compile/static_callback_args.stderr

@@ -0,0 +1,35 @@
+error[E0597]: `lua` does not live long enough
+  --> $DIR/static_callback_args.rs:12:5
+   |
+12 |       lua.create_function(|_, table: Table| {
+   |       -^^
+   |       |
+   |  _____borrowed value does not live long enough
+   | |
+13 | |         BAD_TIME.with(|bt| {
+14 | |             *bt.borrow_mut() = Some(table);
+15 | |         });
+16 | |         Ok(())
+17 | |     })?
+   | |______- argument requires that `lua` is borrowed for `'static`
+...
+32 |   }
+   |   - `lua` dropped here while still borrowed
+
+error[E0505]: cannot move out of `lua` because it is borrowed
+  --> $DIR/static_callback_args.rs:22:10
+   |
+12 |       lua.create_function(|_, table: Table| {
+   |       ---
+   |       |
+   |  _____borrow of `lua` occurs here
+   | |
+13 | |         BAD_TIME.with(|bt| {
+14 | |             *bt.borrow_mut() = Some(table);
+15 | |         });
+16 | |         Ok(())
+17 | |     })?
+   | |______- argument requires that `lua` is borrowed for `'static`
+...
+22 |       drop(lua);
+   |            ^^^ move out of `lua` occurs here

tests/compile_fail.rs

@@ -1,6 +0,0 @@
-#[test]
-#[ignore]
-fn test_compile_fail() {
-    let t = trybuild::TestCases::new();
-    t.compile_fail("tests/compile_fail/*.rs");
-}

tests/compile_fail/lua_norefunwindsafe.stderr

@@ -1,57 +0,0 @@
-error[E0277]: the type `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/lua_norefunwindsafe.rs:7:5
-    |
-7   |     catch_unwind(|| lua.create_table().unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<()>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::cell::UnsafeCell<()>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/lua_norefunwindsafe.rs:7:18: 7:48 lua:&mlua::lua::Lua]`
-
-error[E0277]: the type `std::cell::UnsafeCell<usize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/lua_norefunwindsafe.rs:7:5
-    |
-7   |     catch_unwind(|| lua.create_table().unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<usize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<usize>`
-    = note: required because it appears within the type `std::cell::Cell<usize>`
-    = note: required because it appears within the type `std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>>`
-    = note: required because it appears within the type `std::rc::Rc<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/lua_norefunwindsafe.rs:7:18: 7:48 lua:&mlua::lua::Lua]`
-
-error[E0277]: the type `std::cell::UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/lua_norefunwindsafe.rs:7:5
-    |
-7   |     catch_unwind(|| lua.create_table().unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<mlua::lua::ExtraData>`
-    = note: required because it appears within the type `std::cell::RefCell<mlua::lua::ExtraData>`
-    = note: required because it appears within the type `std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>>`
-    = note: required because it appears within the type `std::rc::Rc<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/lua_norefunwindsafe.rs:7:18: 7:48 lua:&mlua::lua::Lua]`
-
-error[E0277]: the type `std::cell::UnsafeCell<isize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/lua_norefunwindsafe.rs:7:5
-    |
-7   |     catch_unwind(|| lua.create_table().unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<isize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<isize>`
-    = note: required because it appears within the type `std::cell::Cell<isize>`
-    = note: required because it appears within the type `std::cell::RefCell<mlua::lua::ExtraData>`
-    = note: required because it appears within the type `std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>>`
-    = note: required because it appears within the type `std::rc::Rc<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/lua_norefunwindsafe.rs:7:18: 7:48 lua:&mlua::lua::Lua]`

tests/compile_fail/ref_nounwindsafe.stderr

@@ -1,65 +0,0 @@
-error[E0277]: the type `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/ref_nounwindsafe.rs:8:5
-    |
-8   |     catch_unwind(move || table.set("a", "b").unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<()>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::cell::UnsafeCell<()>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `mlua::types::LuaRef<'_>`
-    = note: required because it appears within the type `mlua::table::Table<'_>`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/ref_nounwindsafe.rs:8:18: 8:54 table:mlua::table::Table<'_>]`
-
-error[E0277]: the type `std::cell::UnsafeCell<usize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/ref_nounwindsafe.rs:8:5
-    |
-8   |     catch_unwind(move || table.set("a", "b").unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<usize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<usize>`
-    = note: required because it appears within the type `std::cell::Cell<usize>`
-    = note: required because it appears within the type `std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>>`
-    = note: required because it appears within the type `std::rc::Rc<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `mlua::types::LuaRef<'_>`
-    = note: required because it appears within the type `mlua::table::Table<'_>`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/ref_nounwindsafe.rs:8:18: 8:54 table:mlua::table::Table<'_>]`
-
-error[E0277]: the type `std::cell::UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/ref_nounwindsafe.rs:8:5
-    |
-8   |     catch_unwind(move || table.set("a", "b").unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<mlua::lua::ExtraData>`
-    = note: required because it appears within the type `std::cell::RefCell<mlua::lua::ExtraData>`
-    = note: required because it appears within the type `std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>>`
-    = note: required because it appears within the type `std::rc::Rc<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `mlua::types::LuaRef<'_>`
-    = note: required because it appears within the type `mlua::table::Table<'_>`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/ref_nounwindsafe.rs:8:18: 8:54 table:mlua::table::Table<'_>]`
-
-error[E0277]: the type `std::cell::UnsafeCell<isize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> $DIR/ref_nounwindsafe.rs:8:5
-    |
-8   |     catch_unwind(move || table.set("a", "b").unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<isize>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<isize>`
-    = note: required because it appears within the type `std::cell::Cell<isize>`
-    = note: required because it appears within the type `std::cell::RefCell<mlua::lua::ExtraData>`
-    = note: required because it appears within the type `std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::rc::RcBox<std::cell::RefCell<mlua::lua::ExtraData>>>`
-    = note: required because it appears within the type `std::rc::Rc<std::cell::RefCell<mlua::lua::ExtraData>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `mlua::types::LuaRef<'_>`
-    = note: required because it appears within the type `mlua::table::Table<'_>`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile_fail/ref_nounwindsafe.rs:8:18: 8:54 table:mlua::table::Table<'_>]`

tests/function.rs

@@ -75,3 +75,17 @@ fn test_rust_function() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn test_dump() -> Result<()> {
+    let lua = unsafe { Lua::unsafe_new() };
+
+    let concat_lua = lua
+        .load(r#"function(arg1, arg2) return arg1 .. arg2 end"#)
+        .eval::<Function>()?;
+    let concat = lua.load(&concat_lua.dump(false)?).into_function()?;
+
+    assert_eq!(concat.call::<_, String>(("foo", "bar"))?, "foobar");
+
+    Ok(())
+}

tests/hooks.rs

@@ -0,0 +1,249 @@
+use std::cell::RefCell;
+use std::ops::Deref;
+use std::str;
+use std::sync::{Arc, Mutex};
+
+use mlua::{Error, HookTriggers, Lua, Result, Value};
+
+#[test]
+fn line_counts() -> Result<()> {
+    let output = Arc::new(Mutex::new(Vec::new()));
+    let hook_output = output.clone();
+
+    let lua = Lua::new();
+    lua.set_hook(
+        HookTriggers {
+            every_line: true,
+            ..Default::default()
+        },
+        move |_lua, debug| {
+            hook_output.lock().unwrap().push(debug.curr_line());
+            Ok(())
+        },
+    )?;
+    lua.load(
+        r#"
+            local x = 2 + 3
+            local y = x * 63
+            local z = string.len(x..", "..y)
+        "#,
+    )
+    .exec()?;
+
+    lua.remove_hook();
+
+    let output = output.lock().unwrap();
+    if cfg!(feature = "luajit") && lua.load("jit.version_num").eval::<i64>()? >= 20100 {
+        assert_eq!(*output, vec![2, 3, 4, 0, 4]);
+    } else {
+        assert_eq!(*output, vec![2, 3, 4]);
+    }
+
+    Ok(())
+}
+
+#[test]
+fn function_calls() -> Result<()> {
+    let output = Arc::new(Mutex::new(Vec::new()));
+    let hook_output = output.clone();
+
+    let lua = Lua::new();
+    lua.set_hook(
+        HookTriggers {
+            on_calls: true,
+            ..Default::default()
+        },
+        move |_lua, debug| {
+            let names = debug.names();
+            let source = debug.source();
+            let name = names.name.map(|s| str::from_utf8(s).unwrap().to_owned());
+            let what = source.what.map(|s| str::from_utf8(s).unwrap().to_owned());
+            hook_output.lock().unwrap().push((name, what));
+            Ok(())
+        },
+    )?;
+
+    lua.load(
+        r#"
+            local v = string.len("Hello World")
+        "#,
+    )
+    .exec()?;
+
+    lua.remove_hook();
+
+    let output = output.lock().unwrap();
+    if cfg!(feature = "luajit") && lua.load("jit.version_num").eval::<i64>()? >= 20100 {
+        assert_eq!(
+            *output,
+            vec![
+                (None, Some("main".to_string())),
+                (Some("len".to_string()), Some("Lua".to_string()))
+            ]
+        );
+    } else {
+        assert_eq!(
+            *output,
+            vec![
+                (None, Some("main".to_string())),
+                (Some("len".to_string()), Some("C".to_string()))
+            ]
+        );
+    }
+
+    Ok(())
+}
+
+#[test]
+fn error_within_hook() -> Result<()> {
+    let lua = Lua::new();
+    lua.set_hook(
+        HookTriggers {
+            every_line: true,
+            ..Default::default()
+        },
+        |_lua, _debug| {
+            Err(Error::RuntimeError(
+                "Something happened in there!".to_string(),
+            ))
+        },
+    )?;
+
+    let err = lua
+        .load("x = 1")
+        .exec()
+        .expect_err("panic didn't propagate");
+
+    match err {
+        Error::CallbackError { cause, .. } => match cause.deref() {
+            Error::RuntimeError(s) => assert_eq!(s, "Something happened in there!"),
+            _ => panic!("wrong callback error kind caught"),
+        },
+        _ => panic!("wrong error kind caught"),
+    };
+
+    Ok(())
+}
+
+#[test]
+fn limit_execution_instructions() -> Result<()> {
+    let lua = Lua::new();
+    let mut max_instructions = 10000;
+
+    #[cfg(feature = "luajit")]
+    // For LuaJIT disable JIT, as compiled code does not trigger hooks
+    lua.load("jit.off()").exec()?;
+
+    lua.set_hook(
+        HookTriggers {
+            every_nth_instruction: Some(30),
+            ..Default::default()
+        },
+        move |_lua, _debug| {
+            max_instructions -= 30;
+            if max_instructions < 0 {
+                Err(Error::RuntimeError("time's up".to_string()))
+            } else {
+                Ok(())
+            }
+        },
+    )?;
+
+    lua.globals().set("x", Value::Integer(0))?;
+    let _ = lua
+        .load(
+            r#"
+                for i = 1, 10000 do
+                    x = x + 1
+                end
+            "#,
+        )
+        .exec()
+        .expect_err("instruction limit didn't occur");
+
+    Ok(())
+}
+
+#[test]
+fn hook_removal() -> Result<()> {
+    let lua = Lua::new();
+
+    lua.set_hook(
+        HookTriggers {
+            every_nth_instruction: Some(1),
+            ..Default::default()
+        },
+        |_lua, _debug| {
+            Err(Error::RuntimeError(
+                "this hook should've been removed by this time".to_string(),
+            ))
+        },
+    )?;
+
+    assert!(lua.load("local x = 1").exec().is_err());
+    lua.remove_hook();
+    assert!(lua.load("local x = 1").exec().is_ok());
+
+    Ok(())
+}
+
+#[test]
+fn hook_swap_within_hook() -> Result<()> {
+    thread_local! {
+        static TL_LUA: RefCell<Option<Lua>> = RefCell::new(None);
+    }
+
+    TL_LUA.with(|tl| {
+        *tl.borrow_mut() = Some(Lua::new());
+    });
+
+    TL_LUA.with(|tl| {
+        tl.borrow().as_ref().unwrap().set_hook(
+            HookTriggers {
+                every_line: true,
+                ..Default::default()
+            },
+            move |lua, _debug| {
+                lua.globals().set("ok", 1i64)?;
+                TL_LUA.with(|tl| {
+                    tl.borrow().as_ref().unwrap().set_hook(
+                        HookTriggers {
+                            every_line: true,
+                            ..Default::default()
+                        },
+                        move |lua, _debug| {
+                            lua.load(
+                                r#"
+                                    if ok ~= nil then
+                                        ok = ok + 1
+                                    end
+                                "#,
+                            )
+                            .exec()
+                            .expect("exec failure within hook");
+                            TL_LUA.with(|tl| {
+                                tl.borrow().as_ref().unwrap().remove_hook();
+                            });
+                            Ok(())
+                        },
+                    )
+                })
+            },
+        )
+    })?;
+
+    TL_LUA.with(|tl| {
+        let tl = tl.borrow();
+        let lua = tl.as_ref().unwrap();
+        lua.load(
+            r#"
+                local x = 1
+                x = 2
+                local y = 3
+            "#,
+        )
+        .exec()?;
+        assert_eq!(lua.globals().get::<_, i64>("ok")?, 2);
+        Ok(())
+    })
+}

tests/memory.rs

@@ -1,13 +1,44 @@
-use std::rc::Rc;
+use std::sync::Arc;
 
 use mlua::{Lua, Result, UserData};
 
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+use mlua::Error;
+
+#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+#[test]
+fn test_memory_limit() -> Result<()> {
+    let lua = Lua::new();
+
+    let initial_memory = lua.used_memory();
+    assert!(
+        initial_memory > 0,
+        "used_memory reporting is wrong, lua uses memory for stdlib"
+    );
+
+    let f = lua
+        .load("local t = {}; for i = 1,10000 do t[i] = i end")
+        .into_function()?;
+    f.call::<_, ()>(()).expect("should trigger no memory limit");
+
+    lua.set_memory_limit(initial_memory + 10000)?;
+    match f.call::<_, ()>(()) {
+        Err(Error::MemoryError(_)) => {}
+        something_else => panic!("did not trigger memory error: {:?}", something_else),
+    };
+
+    lua.set_memory_limit(0)?;
+    f.call::<_, ()>(()).expect("should trigger no memory limit");
+
+    Ok(())
+}
+
 #[test]
 fn test_gc_control() -> Result<()> {
     let lua = Lua::new();
     let globals = lua.globals();
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     {
         assert!(lua.gc_is_running());
         lua.gc_stop();
@@ -16,17 +47,17 @@ fn test_gc_control() -> Result<()> {
         assert!(lua.gc_is_running());
     }
 
-    struct MyUserdata(Rc<()>);
+    struct MyUserdata(Arc<()>);
     impl UserData for MyUserdata {}
 
-    let rc = Rc::new(());
+    let rc = Arc::new(());
     globals.set("userdata", lua.create_userdata(MyUserdata(rc.clone()))?)?;
     globals.raw_remove("userdata")?;
 
-    assert_eq!(Rc::strong_count(&rc), 2);
+    assert_eq!(Arc::strong_count(&rc), 2);
     lua.gc_collect()?;
     lua.gc_collect()?;
-    assert_eq!(Rc::strong_count(&rc), 1);
+    assert_eq!(Arc::strong_count(&rc), 1);
 
     Ok(())
 }

tests/module/.cargo/config

@@ -0,0 +1,5 @@
+[target.x86_64-apple-darwin]
+rustflags = ["-C", "link-args=-rdynamic"]
+
+[target.x86_64-unknown-linux-gnu]
+rustflags = ["-C", "link-args=-rdynamic"]

tests/module/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "module_runner"
+version = "0.0.0"
+authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
+edition = "2018"
+
+[features]
+lua54 = ["mlua/lua54"]
+lua53 = ["mlua/lua53"]
+lua52 = ["mlua/lua52"]
+lua51 = ["mlua/lua51"]
+luajit = ["mlua/luajit"]
+vendored = ["mlua/vendored"]
+
+[dependencies]
+mlua = { path = "../.." }

tests/module/tests/load.rs

@@ -0,0 +1,82 @@
+use std::env;
+use std::path::PathBuf;
+
+use mlua::{Lua, Result};
+
+#[test]
+fn test_module() -> Result<()> {
+    let lua = make_lua()?;
+    lua.load(
+        r#"
+        local mod = require("rust_module")
+        assert(mod.sum(2,2) == 4)
+    "#,
+    )
+    .exec()
+}
+
+#[cfg(any(
+    feature = "lua54",
+    feature = "lua53",
+    feature = "lua52",
+    feature = "lua51"
+))]
+#[test]
+fn test_module_from_thread() -> Result<()> {
+    let lua = make_lua()?;
+    lua.load(
+        r#"
+        local mod
+
+        local co = coroutine.create(function(a, b)
+            mod = require("rust_module")
+            assert(mod.sum(a, b) == a + b)
+        end)
+
+        coroutine.resume(co, 3, 5)
+        collectgarbage()
+
+        assert(mod.used_memory() > 0)
+    "#,
+    )
+    .exec()
+}
+
+fn make_lua() -> Result<Lua> {
+    let (dylib_path, dylib_ext, separator);
+    if cfg!(target_os = "macos") {
+        dylib_path = env::var("DYLD_FALLBACK_LIBRARY_PATH").unwrap();
+        dylib_ext = "dylib";
+        separator = ":";
+    } else if cfg!(target_os = "linux") {
+        dylib_path = env::var("LD_LIBRARY_PATH").unwrap();
+        dylib_ext = "so";
+        separator = ":";
+    } else if cfg!(target_os = "windows") {
+        dylib_path = env::var("PATH").unwrap();
+        dylib_ext = "dll";
+        separator = ";";
+    } else {
+        panic!("unknown target os");
+    };
+
+    let mut cpath = dylib_path
+        .split(separator)
+        .take(3)
+        .map(|p| {
+            let mut path = PathBuf::from(p);
+            path.push(format!("lib?.{}", dylib_ext));
+            path.to_str().unwrap().to_owned()
+        })
+        .collect::<Vec<_>>()
+        .join(";");
+
+    if cfg!(target_os = "windows") {
+        cpath = cpath.replace("\\", "\\\\");
+        cpath = cpath.replace("lib?.", "?.");
+    }
+
+    let lua = unsafe { Lua::unsafe_new() }; // To be able to load C modules
+    lua.load(&format!("package.cpath = \"{}\"", cpath)).exec()?;
+    Ok(lua)
+}

tests/scope.rs

@@ -0,0 +1,275 @@
+use std::cell::Cell;
+use std::rc::Rc;
+
+use mlua::{
+    AnyUserData, Error, Function, Lua, MetaMethod, Result, String, UserData, UserDataMethods,
+};
+
+#[test]
+fn scope_func() -> Result<()> {
+    let lua = Lua::new();
+
+    let rc = Rc::new(Cell::new(0));
+    lua.scope(|scope| {
+        let r = rc.clone();
+        let f = scope.create_function(move |_, ()| {
+            r.set(42);
+            Ok(())
+        })?;
+        lua.globals().set("bad", f.clone())?;
+        f.call::<_, ()>(())?;
+        assert_eq!(Rc::strong_count(&rc), 2);
+        Ok(())
+    })?;
+    assert_eq!(rc.get(), 42);
+    assert_eq!(Rc::strong_count(&rc), 1);
+
+    match lua.globals().get::<_, Function>("bad")?.call::<_, ()>(()) {
+        Err(Error::CallbackError { .. }) => {}
+        r => panic!("improper return for destructed function: {:?}", r),
+    };
+
+    Ok(())
+}
+
+#[test]
+fn scope_drop() -> Result<()> {
+    let lua = Lua::new();
+
+    struct MyUserdata(Rc<()>);
+    impl UserData for MyUserdata {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_method("method", |_, _, ()| Ok(()));
+        }
+    }
+
+    let rc = Rc::new(());
+
+    lua.scope(|scope| {
+        lua.globals()
+            .set("static_ud", scope.create_userdata(MyUserdata(rc.clone()))?)?;
+        assert_eq!(Rc::strong_count(&rc), 2);
+        Ok(())
+    })?;
+    assert_eq!(Rc::strong_count(&rc), 1);
+
+    match lua.load("static_ud:method()").exec() {
+        Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+            Error::CallbackDestructed => {}
+            e => panic!("expected CallbackDestructed, got {:?}", e),
+        },
+        r => panic!("improper return for destructed userdata: {:?}", r),
+    };
+
+    let static_ud = lua.globals().get::<_, AnyUserData>("static_ud")?;
+    match static_ud.borrow::<MyUserdata>() {
+        Ok(_) => panic!("borrowed destructed userdata"),
+        Err(Error::UserDataDestructed) => {}
+        Err(e) => panic!("expected UserDataDestructed, got {:?}", e),
+    }
+
+    // Check non-static UserData drop
+    struct MyUserDataRef<'a>(&'a Cell<i64>);
+
+    impl<'a> UserData for MyUserDataRef<'a> {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_method("inc", |_, data, ()| {
+                data.0.set(data.0.get() + 1);
+                Ok(())
+            });
+        }
+    }
+
+    let i = Cell::new(1);
+    lua.scope(|scope| {
+        lua.globals().set(
+            "nonstatic_ud",
+            scope.create_nonstatic_userdata(MyUserDataRef(&i))?,
+        )
+    })?;
+
+    match lua.load("nonstatic_ud:inc(1)").exec() {
+        Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+            Error::CallbackDestructed => {}
+            e => panic!("expected CallbackDestructed, got {:?}", e),
+        },
+        r => panic!("improper return for destructed userdata: {:?}", r),
+    };
+
+    let nonstatic_ud = lua.globals().get::<_, AnyUserData>("nonstatic_ud")?;
+    match nonstatic_ud.borrow::<MyUserDataRef>() {
+        Ok(_) => panic!("borrowed destructed userdata"),
+        Err(Error::UserDataDestructed) => {}
+        Err(e) => panic!("expected UserDataDestructed, got {:?}", e),
+    }
+
+    Ok(())
+}
+
+#[test]
+fn scope_capture() -> Result<()> {
+    let lua = Lua::new();
+
+    let mut i = 0;
+    lua.scope(|scope| {
+        scope
+            .create_function_mut(|_, ()| {
+                i = 42;
+                Ok(())
+            })?
+            .call::<_, ()>(())
+    })?;
+    assert_eq!(i, 42);
+
+    Ok(())
+}
+
+#[test]
+fn outer_lua_access() -> Result<()> {
+    let lua = Lua::new();
+
+    let table = lua.create_table()?;
+    lua.scope(|scope| {
+        scope
+            .create_function_mut(|_, ()| table.set("a", "b"))?
+            .call::<_, ()>(())
+    })?;
+    assert_eq!(table.get::<_, String>("a")?, "b");
+
+    Ok(())
+}
+
+#[test]
+fn scope_userdata_methods() -> Result<()> {
+    struct MyUserData<'a>(&'a Cell<i64>);
+
+    impl<'a> UserData for MyUserData<'a> {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_method("inc", |_, data, ()| {
+                data.0.set(data.0.get() + 1);
+                Ok(())
+            });
+
+            methods.add_method("dec", |_, data, ()| {
+                data.0.set(data.0.get() - 1);
+                Ok(())
+            });
+        }
+    }
+
+    let lua = Lua::new();
+
+    let i = Cell::new(42);
+    let f: Function = lua
+        .load(
+            r#"
+            function(u)
+                u:inc()
+                u:inc()
+                u:inc()
+                u:dec()
+            end
+        "#,
+        )
+        .eval()?;
+
+    lua.scope(|scope| f.call::<_, ()>(scope.create_nonstatic_userdata(MyUserData(&i))?))?;
+
+    assert_eq!(i.get(), 44);
+
+    Ok(())
+}
+
+#[test]
+fn scope_userdata_functions() -> Result<()> {
+    struct MyUserData<'a>(&'a i64);
+
+    impl<'a> UserData for MyUserData<'a> {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_meta_function(MetaMethod::Add, |lua, ()| {
+                let globals = lua.globals();
+                globals.set("i", globals.get::<_, i64>("i")? + 1)?;
+                Ok(())
+            });
+            methods.add_meta_function(MetaMethod::Sub, |lua, ()| {
+                let globals = lua.globals();
+                globals.set("i", globals.get::<_, i64>("i")? + 1)?;
+                Ok(())
+            });
+        }
+    }
+
+    let lua = Lua::new();
+
+    let dummy = 0;
+    let f = lua
+        .load(
+            r#"
+            i = 0
+            return function(u)
+                _ = u + u
+                _ = u - 1
+                _ = 1 + u
+            end
+        "#,
+        )
+        .eval::<Function>()?;
+
+    lua.scope(|scope| f.call::<_, ()>(scope.create_nonstatic_userdata(MyUserData(&dummy))?))?;
+
+    assert_eq!(lua.globals().get::<_, i64>("i")?, 3);
+
+    Ok(())
+}
+
+#[test]
+fn scope_userdata_mismatch() -> Result<()> {
+    struct MyUserData<'a>(&'a Cell<i64>);
+
+    impl<'a> UserData for MyUserData<'a> {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_method("inc", |_, data, ()| {
+                data.0.set(data.0.get() + 1);
+                Ok(())
+            });
+        }
+    }
+
+    let lua = Lua::new();
+
+    lua.load(
+        r#"
+        function okay(a, b)
+            a.inc(a)
+            b.inc(b)
+        end
+        function bad(a, b)
+            a.inc(b)
+        end
+    "#,
+    )
+    .exec()?;
+
+    let a = Cell::new(1);
+    let b = Cell::new(1);
+
+    let okay: Function = lua.globals().get("okay")?;
+    let bad: Function = lua.globals().get("bad")?;
+
+    lua.scope(|scope| {
+        let au = scope.create_nonstatic_userdata(MyUserData(&a))?;
+        let bu = scope.create_nonstatic_userdata(MyUserData(&b))?;
+        assert!(okay.call::<_, ()>((au.clone(), bu.clone())).is_ok());
+        match bad.call::<_, ()>((au, bu)) {
+            Err(Error::CallbackError { ref cause, .. }) => match *cause.as_ref() {
+                Error::UserDataTypeMismatch => {}
+                ref other => panic!("wrong error type {:?}", other),
+            },
+            Err(other) => panic!("wrong error type {:?}", other),
+            Ok(_) => panic!("incorrectly returned Ok"),
+        }
+        Ok(())
+    })?;
+
+    Ok(())
+}

tests/serde.rs

@@ -0,0 +1,343 @@
+#![cfg(feature = "serialize")]
+
+use mlua::{Error, Lua, LuaSerdeExt, Result as LuaResult, UserData, Value};
+use serde::{Deserialize, Serialize};
+
+#[test]
+fn test_serialize() -> Result<(), Box<dyn std::error::Error>> {
+    #[derive(Serialize)]
+    struct MyUserData(i64, String);
+
+    impl UserData for MyUserData {}
+
+    let lua = Lua::new();
+    let globals = lua.globals();
+
+    let ud = lua.create_ser_userdata(MyUserData(123, "test userdata".into()))?;
+    globals.set("ud", ud)?;
+    globals.set("null", lua.null()?)?;
+
+    let empty_array = lua.create_table()?;
+    empty_array.set_metatable(Some(lua.array_metatable()?));
+    globals.set("empty_array", empty_array)?;
+
+    let val = lua
+        .load(
+            r#"
+        {
+            _bool = true,
+            _integer = 123,
+            _number = 321.99,
+            _string = "test string serialization",
+            _table_arr = {nil, "value 1", nil, "value 2", {}},
+            _table_map = {["table"] = "map", ["null"] = null},
+            _bytes = "\240\040\140\040",
+            _userdata = ud,
+            _null = null,
+            _empty_map = {},
+            _empty_array = empty_array,
+        }
+    "#,
+        )
+        .eval::<Value>()?;
+
+    let json = serde_json::json!({
+        "_bool": true,
+        "_integer": 123,
+        "_number": 321.99,
+        "_string": "test string serialization",
+        "_table_arr": [null, "value 1", null, "value 2", {}],
+        "_table_map": {"table": "map", "null": null},
+        "_bytes": [240, 40, 140, 40],
+        "_userdata": [123, "test userdata"],
+        "_null": null,
+        "_empty_map": {},
+        "_empty_array": [],
+    });
+
+    assert_eq!(serde_json::to_value(&val)?, json);
+
+    // Test to-from loop
+    let val = lua.to_value(&json)?;
+    let expected_json = lua.from_value::<serde_json::Value>(val)?;
+    assert_eq!(expected_json, json);
+
+    Ok(())
+}
+
+#[test]
+fn test_serialize_in_scope() -> LuaResult<()> {
+    #[derive(Serialize, Clone)]
+    struct MyUserData(i64, String);
+
+    impl UserData for MyUserData {}
+
+    let lua = Lua::new();
+    lua.scope(|scope| {
+        let ud = scope.create_ser_userdata(MyUserData(-5, "test userdata".into()))?;
+        assert_eq!(
+            serde_json::to_value(&ud).unwrap(),
+            serde_json::json!((-5, "test userdata"))
+        );
+        Ok(())
+    })?;
+
+    lua.scope(|scope| {
+        let ud = scope.create_ser_userdata(MyUserData(-5, "test userdata".into()))?;
+        lua.globals().set("ud", ud)
+    })?;
+    let val = lua.load("ud").eval::<Value>()?;
+    match serde_json::to_value(&val) {
+        Ok(v) => panic!("expected destructed error, got {}", v),
+        Err(e) if e.to_string().contains("destructed") => {}
+        Err(e) => panic!("expected destructed error, got {}", e),
+    }
+
+    struct MyUserDataRef<'a>(&'a ());
+
+    impl<'a> UserData for MyUserDataRef<'a> {}
+
+    lua.scope(|scope| {
+        let ud = scope.create_nonstatic_userdata(MyUserDataRef(&()))?;
+        match serde_json::to_value(&ud) {
+            Ok(v) => panic!("expected serialization error, got {}", v),
+            Err(serde_json::Error { .. }) => {}
+        };
+        Ok(())
+    })?;
+
+    Ok(())
+}
+
+#[test]
+fn test_serialize_failure() -> Result<(), Box<dyn std::error::Error>> {
+    #[derive(Serialize)]
+    struct MyUserData(i64);
+
+    impl UserData for MyUserData {}
+
+    let lua = Lua::new();
+
+    let ud = Value::UserData(lua.create_userdata(MyUserData(123))?);
+    match serde_json::to_value(&ud) {
+        Ok(v) => panic!("expected serialization error, got {}", v),
+        Err(serde_json::Error { .. }) => {}
+    }
+
+    let func = lua.create_function(|_, _: ()| Ok(()))?;
+    match serde_json::to_value(&Value::Function(func.clone())) {
+        Ok(v) => panic!("expected serialization error, got {}", v),
+        Err(serde_json::Error { .. }) => {}
+    }
+
+    let thr = lua.create_thread(func)?;
+    match serde_json::to_value(&Value::Thread(thr)) {
+        Ok(v) => panic!("expected serialization error, got {}", v),
+        Err(serde_json::Error { .. }) => {}
+    }
+
+    Ok(())
+}
+
+#[test]
+fn test_to_value_struct() -> LuaResult<()> {
+    let lua = Lua::new();
+    let globals = lua.globals();
+    globals.set("null", lua.null()?)?;
+
+    #[derive(Serialize)]
+    struct Test {
+        name: String,
+        key: i64,
+        data: Option<bool>,
+    }
+
+    let test = Test {
+        name: "alex".to_string(),
+        key: -16,
+        data: None,
+    };
+
+    globals.set("value", lua.to_value(&test)?)?;
+    lua.load(
+        r#"
+            assert(value["name"] == "alex")
+            assert(value["key"] == -16)
+            assert(value["data"] == null)
+        "#,
+    )
+    .exec()
+}
+
+#[test]
+fn test_to_value_enum() -> LuaResult<()> {
+    let lua = Lua::new();
+    let globals = lua.globals();
+    globals.set("null", lua.null()?)?;
+
+    #[derive(Serialize)]
+    struct Test {
+        name: String,
+        key: i64,
+        data: Option<bool>,
+    }
+
+    let test = Test {
+        name: "alex".to_string(),
+        key: -16,
+        data: None,
+    };
+
+    globals.set("value", lua.to_value(&test)?)?;
+    lua.load(
+        r#"
+            assert(value["name"] == "alex")
+            assert(value["key"] == -16)
+            assert(value["data"] == null)
+        "#,
+    )
+    .exec()?;
+
+    #[derive(Serialize)]
+    enum E {
+        Unit,
+        Integer(u32),
+        Tuple(u32, u32),
+        Struct { a: u32 },
+    }
+
+    let u = E::Unit;
+    globals.set("value", lua.to_value(&u)?)?;
+    lua.load(r#"assert(value == "Unit")"#).exec()?;
+
+    let n = E::Integer(1);
+    globals.set("value", lua.to_value(&n)?)?;
+    lua.load(r#"assert(value["Integer"] == 1)"#).exec()?;
+
+    let t = E::Tuple(1, 2);
+    globals.set("value", lua.to_value(&t)?)?;
+    lua.load(
+        r#"
+            assert(value["Tuple"][1] == 1)
+            assert(value["Tuple"][2] == 2)
+        "#,
+    )
+    .exec()?;
+
+    let s = E::Struct { a: 1 };
+    globals.set("value", lua.to_value(&s)?)?;
+    lua.load(r#"assert(value["Struct"]["a"] == 1)"#).exec()?;
+    Ok(())
+}
+
+#[test]
+fn test_from_value_struct() -> Result<(), Box<dyn std::error::Error>> {
+    let lua = Lua::new();
+
+    #[derive(Deserialize, PartialEq, Debug)]
+    struct Test {
+        int: u32,
+        seq: Vec<String>,
+        map: std::collections::HashMap<i32, i32>,
+        empty: Vec<()>,
+        tuple: (u8, u8, u8),
+    }
+
+    let value = lua
+        .load(
+            r#"
+            {
+                int = 1,
+                seq = {"a", "b"},
+                map = {2, [4] = 1},
+                empty = {},
+                tuple = {10, 20, 30},
+            }
+        "#,
+        )
+        .eval::<Value>()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(
+        Test {
+            int: 1,
+            seq: vec!["a".into(), "b".into()],
+            map: vec![(1, 2), (4, 1)].into_iter().collect(),
+            empty: vec![],
+            tuple: (10, 20, 30),
+        },
+        got
+    );
+
+    Ok(())
+}
+
+#[test]
+fn test_from_value_enum() -> Result<(), Box<dyn std::error::Error>> {
+    let lua = Lua::new();
+
+    #[derive(Deserialize, PartialEq, Debug)]
+    enum E {
+        Unit,
+        Integer(u32),
+        Tuple(u32, u32),
+        Struct { a: u32 },
+    }
+
+    let value = lua.load(r#""Unit""#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(E::Unit, got);
+
+    let value = lua.load(r#"{Integer = 1}"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(E::Integer(1), got);
+
+    let value = lua.load(r#"{Tuple = {1, 2}}"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(E::Tuple(1, 2), got);
+
+    let value = lua.load(r#"{Struct = {a = 3}}"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(E::Struct { a: 3 }, got);
+
+    Ok(())
+}
+
+#[test]
+fn test_from_value_enum_untagged() -> Result<(), Box<dyn std::error::Error>> {
+    let lua = Lua::new();
+    lua.globals().set("null", lua.null()?)?;
+
+    #[derive(Deserialize, PartialEq, Debug)]
+    #[serde(untagged)]
+    enum Eut {
+        Unit,
+        Integer(u64),
+        Tuple(u32, u32),
+        Struct { a: u32 },
+    }
+
+    let value = lua.load(r#"null"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(Eut::Unit, got);
+
+    let value = lua.load(r#"1"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(Eut::Integer(1), got);
+
+    let value = lua.load(r#"{3, 1}"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(Eut::Tuple(3, 1), got);
+
+    let value = lua.load(r#"{a = 10}"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(Eut::Struct { a: 10 }, got);
+
+    let value = lua.load(r#"{b = 12}"#).eval()?;
+    match lua.from_value::<Eut>(value) {
+        Ok(v) => panic!("expected Error::DeserializeError, got {:?}", v),
+        Err(Error::DeserializeError(_)) => {}
+        Err(e) => panic!("expected Error::DeserializeError, got {}", e),
+    }
+
+    Ok(())
+}

tests/table.rs

@@ -109,6 +109,47 @@ fn test_table() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_table_sequence_from() -> Result<()> {
+    let lua = Lua::new();
+
+    let get_table = lua.create_function(|_, t: Table| Ok(t))?;
+
+    assert_eq!(
+        get_table
+            .call::<_, Table>(vec![1, 2, 3])?
+            .sequence_values()
+            .collect::<Result<Vec<i64>>>()?,
+        vec![1, 2, 3]
+    );
+
+    assert_eq!(
+        get_table
+            .call::<_, Table>([1, 2, 3].as_ref())?
+            .sequence_values()
+            .collect::<Result<Vec<i64>>>()?,
+        vec![1, 2, 3]
+    );
+
+    assert_eq!(
+        get_table
+            .call::<_, Table>([1, 2, 3])?
+            .sequence_values()
+            .collect::<Result<Vec<i64>>>()?,
+        vec![1, 2, 3]
+    );
+
+    assert_eq!(
+        get_table
+            .call::<_, Table>(&[1, 2, 3])?
+            .sequence_values()
+            .collect::<Result<Vec<i64>>>()?,
+        vec![1, 2, 3]
+    );
+
+    Ok(())
+}
+
 #[test]
 fn test_table_scope() -> Result<()> {
     let lua = Lua::new();

tests/tests.rs

@@ -1,12 +1,83 @@
 use std::iter::FromIterator;
-use std::panic::catch_unwind;
-use std::rc::Rc;
+use std::panic::{catch_unwind, AssertUnwindSafe};
+use std::sync::Arc;
 use std::{error, f32, f64, fmt};
 
 use mlua::{
-    Error, ExternalError, Function, Lua, Nil, Result, String, Table, UserData, Value, Variadic,
+    ChunkMode, Error, ExternalError, Function, Lua, Nil, Result, StdLib, String, Table, UserData,
+    Value, Variadic,
 };
 
+#[test]
+fn test_safety() -> Result<()> {
+    let lua = Lua::new();
+    assert!(lua.load(r#"require "debug""#).exec().is_err());
+    match lua.load_from_std_lib(StdLib::DEBUG) {
+        Err(Error::SafetyError(_)) => {}
+        Err(e) => panic!("expected SafetyError, got {:?}", e),
+        Ok(_) => panic!("expected SafetyError, got no error"),
+    }
+    drop(lua);
+
+    let lua = unsafe { Lua::unsafe_new() };
+    assert!(lua.load(r#"require "debug""#).exec().is_ok());
+    drop(lua);
+
+    match Lua::new_with(StdLib::DEBUG) {
+        Err(Error::SafetyError(_)) => {}
+        Err(e) => panic!("expected SafetyError, got {:?}", e),
+        Ok(_) => panic!("expected SafetyError, got new Lua state"),
+    }
+
+    let lua = Lua::new();
+    match lua.load(r#"package.loadlib()"#).exec() {
+        Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+            Error::SafetyError(_) => {}
+            e => panic!("expected SafetyError cause, got {:?}", e),
+        },
+        Err(e) => panic!("expected CallbackError, got {:?}", e),
+        Ok(_) => panic!("expected CallbackError, got no error"),
+    };
+    match lua.load(r#"require "fake_ffi""#).exec() {
+        Err(Error::RuntimeError(msg)) => assert!(msg.contains("can't load C modules in safe mode")),
+        Err(e) => panic!("expected RuntimeError, got {:?}", e),
+        Ok(_) => panic!("expected RuntimeError, got no error"),
+    }
+
+    match lua.load("1 + 1").set_mode(ChunkMode::Binary).exec() {
+        Err(Error::SafetyError(msg)) => {
+            assert!(msg.contains("binary chunks are disabled in safe mode"))
+        }
+        Err(e) => panic!("expected SafetyError, got {:?}", e),
+        Ok(_) => panic!("expected SafetyError, got no error"),
+    }
+
+    let bytecode = lua.load("return 1 + 1").into_function()?.dump(true)?;
+    match lua.load(&bytecode).exec() {
+        Err(Error::SafetyError(msg)) => {
+            assert!(msg.contains("binary chunks are disabled in safe mode"))
+        }
+        Err(e) => panic!("expected SafetyError, got {:?}", e),
+        Ok(_) => panic!("expected SafetyError, got no error"),
+    }
+    drop(lua);
+
+    // Test safety rules after dynamically loading `package` library
+    let lua = Lua::new_with(StdLib::NONE)?;
+    assert!(lua.globals().get::<_, Option<Value>>("require")?.is_none());
+    lua.load_from_std_lib(StdLib::PACKAGE)?;
+    match lua.load(r#"package.loadlib()"#).exec() {
+        Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+            Error::SafetyError(_) => {}
+            e => panic!("expected SafetyError cause, got {:?}", e),
+        },
+        Err(e) => panic!("expected CallbackError, got {:?}", e),
+        Ok(_) => panic!("expected CallbackError, got no error"),
+    };
+
+    Ok(())
+}
+
 #[test]
 fn test_load() -> Result<()> {
     let lua = Lua::new();
@@ -75,6 +146,41 @@ fn test_eval() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_load_mode() -> Result<()> {
+    let lua = unsafe { Lua::unsafe_new() };
+
+    assert_eq!(
+        lua.load("1 + 1").set_mode(ChunkMode::Text).eval::<i32>()?,
+        2
+    );
+    match lua.load("1 + 1").set_mode(ChunkMode::Binary).exec() {
+        Ok(_) => panic!("expected SyntaxError, got no error"),
+        Err(Error::SyntaxError { message: msg, .. }) => {
+            assert!(msg.contains("attempt to load a text chunk"))
+        }
+        Err(e) => panic!("expected SyntaxError, got {:?}", e),
+    };
+
+    let bytecode = lua.load("return 1 + 1").into_function()?.dump(true)?;
+    assert_eq!(lua.load(&bytecode).eval::<i32>()?, 2);
+    assert_eq!(
+        lua.load(&bytecode)
+            .set_mode(ChunkMode::Binary)
+            .eval::<i32>()?,
+        2
+    );
+    match lua.load(&bytecode).set_mode(ChunkMode::Text).exec() {
+        Ok(_) => panic!("expected SyntaxError, got no error"),
+        Err(Error::SyntaxError { message: msg, .. }) => {
+            assert!(msg.contains("attempt to load a binary chunk"))
+        }
+        Err(e) => panic!("expected SyntaxError, got {:?}", e),
+    };
+
+    Ok(())
+}
+
 #[test]
 fn test_lua_multi() -> Result<()> {
     let lua = Lua::new();
@@ -266,62 +372,92 @@ fn test_error() -> Result<()> {
 
     assert!(understand_recursion.call::<_, ()>(()).is_err());
 
-    match catch_unwind(|| -> Result<()> {
-        let lua = Lua::new();
-        let globals = lua.globals();
+    Ok(())
+}
 
+#[test]
+fn test_panic() -> Result<()> {
+    fn make_lua() -> Result<Lua> {
+        let lua = Lua::new();
+        let rust_panic_function =
+            lua.create_function(|_, ()| -> Result<()> { panic!("rust panic") })?;
+        lua.globals()
+            .set("rust_panic_function", rust_panic_function)?;
+        Ok(lua)
+    }
+
+    // Test triggerting Lua error passing Rust panic (must be resumed)
+    {
+        let lua = make_lua()?;
+
+        match catch_unwind(AssertUnwindSafe(|| -> Result<()> {
+            lua.load(
+                r#"
+                _, err = pcall(rust_panic_function)
+                error(err)
+            "#,
+            )
+            .exec()
+        })) {
+            Ok(Ok(_)) => panic!("no panic was detected"),
+            Ok(Err(e)) => panic!("error during panic test {:?}", e),
+            Err(p) => assert!(*p.downcast::<&str>().unwrap() == "rust panic"),
+        };
+
+        // Trigger same panic again
+        match lua.load("error(err)").exec() {
+            Ok(_) => panic!("no error was detected"),
+            Err(Error::PreviouslyResumedPanic) => {}
+            Err(e) => panic!("expected PreviouslyResumedPanic, got {:?}", e),
+        }
+    }
+
+    // Test returning Rust panic (must be resumed)
+    {
+        let lua = make_lua()?;
+        match catch_unwind(AssertUnwindSafe(|| -> Result<()> {
+            let _catched_panic = lua
+                .load(
+                    r#"
+                    -- Set global
+                    _, err = pcall(rust_panic_function)
+                    return err
+                "#,
+                )
+                .eval::<Value>()?;
+            Ok(())
+        })) {
+            Ok(_) => panic!("no panic was detected"),
+            Err(_) => {}
+        };
+
+        assert!(lua.globals().get::<_, Value>("err")? == Value::Nil);
+        match lua.load("tostring(err)").exec() {
+            Ok(_) => panic!("no error was detected"),
+            Err(Error::CallbackError { ref cause, .. }) => match cause.as_ref() {
+                Error::PreviouslyResumedPanic => {}
+                e => panic!("expected PreviouslyResumedPanic, got {:?}", e),
+            },
+            Err(e) => panic!("expected CallbackError, got {:?}", e),
+        }
+    }
+
+    // Test representing rust panic as a string
+    match catch_unwind(|| -> Result<()> {
+        let lua = make_lua()?;
         lua.load(
             r#"
-            function rust_panic()
-                local _, err = pcall(function () rust_panic_function() end)
-                if err ~= nil then
-                    error(err)
-                end
-            end
+            local _, err = pcall(rust_panic_function)
+            error(tostring(err))
         "#,
         )
-        .exec()?;
-        let rust_panic_function =
-            lua.create_function(|_, ()| -> Result<()> { panic!("test_panic") })?;
-        globals.set("rust_panic_function", rust_panic_function)?;
-
-        let rust_panic = globals.get::<_, Function>("rust_panic")?;
-
-        rust_panic.call::<_, ()>(())
-    }) {
-        Ok(Ok(_)) => panic!("no panic was detected"),
-        Ok(Err(e)) => panic!("error during panic test {:?}", e),
-        Err(p) => assert!(*p.downcast::<&str>().unwrap() == "test_panic"),
-    };
-
-    match catch_unwind(|| -> Result<()> {
-        let lua = Lua::new();
-        let globals = lua.globals();
-
-        lua.load(
-            r#"
-            function rust_panic()
-                local _, err = pcall(function () rust_panic_function() end)
-                if err ~= nil then
-                    error(tostring(err))
-                end
-            end
-        "#,
-        )
-        .exec()?;
-        let rust_panic_function =
-            lua.create_function(|_, ()| -> Result<()> { panic!("test_panic") })?;
-        globals.set("rust_panic_function", rust_panic_function)?;
-
-        let rust_panic = globals.get::<_, Function>("rust_panic")?;
-
-        rust_panic.call::<_, ()>(())
+        .exec()
     }) {
         Ok(Ok(_)) => panic!("no error was detected"),
         Ok(Err(Error::RuntimeError(_))) => {}
-        Ok(Err(e)) => panic!("unexpected error during panic test {:?}", e),
+        Ok(Err(e)) => panic!("expected RuntimeError, got {:?}", e),
         Err(_) => panic!("panic was detected"),
-    };
+    }
 
     Ok(())
 }
@@ -389,7 +525,7 @@ fn test_num_conversion() -> Result<()> {
 
     assert_eq!(lua.load("1.0").eval::<i64>()?, 1);
     assert_eq!(lua.load("1.0").eval::<f64>()?, 1.0);
-    #[cfg(feature = "lua53")]
+    #[cfg(any(feature = "lua54", feature = "lua53"))]
     assert_eq!(lua.load("1.0").eval::<String>()?, "1.0");
     #[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
     assert_eq!(lua.load("1.0").eval::<String>()?, "1");
@@ -405,7 +541,9 @@ fn test_num_conversion() -> Result<()> {
     assert!(lua.load("math.huge").eval::<i64>().is_err());
 
     assert_eq!(lua.unpack::<f64>(lua.pack(f32::MAX)?)?, f32::MAX as f64);
-    assert!(lua.unpack::<f32>(lua.pack(f64::MAX)?).is_err());
+    assert_eq!(lua.unpack::<f64>(lua.pack(f32::MIN)?)?, f32::MIN as f64);
+    assert_eq!(lua.unpack::<f32>(lua.pack(f64::MAX)?)?, f32::INFINITY);
+    assert_eq!(lua.unpack::<f32>(lua.pack(f64::MIN)?)?, f32::NEG_INFINITY);
 
     assert_eq!(lua.unpack::<i128>(lua.pack(1i128 << 64)?)?, 1i128 << 64);
 
@@ -466,7 +604,12 @@ fn test_pcall_xpcall() -> Result<()> {
     assert_eq!(globals.get::<_, String>("pcall_error")?, "testerror");
 
     assert_eq!(globals.get::<_, bool>("xpcall_statusr")?, false);
-    #[cfg(any(feature = "lua53", feature = "lua52", feature = "luajit"))]
+    #[cfg(any(
+        feature = "lua54",
+        feature = "lua53",
+        feature = "lua52",
+        feature = "luajit"
+    ))]
     assert_eq!(
         globals.get::<_, std::string::String>("xpcall_error")?,
         "testerror"
@@ -584,22 +727,22 @@ fn test_registry_value() -> Result<()> {
 
 #[test]
 fn test_drop_registry_value() -> Result<()> {
-    struct MyUserdata(Rc<()>);
+    struct MyUserdata(Arc<()>);
 
     impl UserData for MyUserdata {}
 
     let lua = Lua::new();
-    let rc = Rc::new(());
+    let rc = Arc::new(());
 
     let r = lua.create_registry_value(MyUserdata(rc.clone()))?;
-    assert_eq!(Rc::strong_count(&rc), 2);
+    assert_eq!(Arc::strong_count(&rc), 2);
 
     drop(r);
     lua.expire_registry_values();
 
     lua.load(r#"collectgarbage("collect")"#).exec()?;
 
-    assert_eq!(Rc::strong_count(&rc), 1);
+    assert_eq!(Arc::strong_count(&rc), 1);
 
     Ok(())
 }
@@ -799,7 +942,7 @@ fn context_thread() -> Result<()> {
         )
         .into_function()?;
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     f.call::<_, ()>(lua.current_thread())?;
 
     #[cfg(any(feature = "lua51", feature = "luajit"))]
@@ -828,3 +971,15 @@ fn context_thread_51() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+#[cfg(feature = "luajit")]
+fn test_jit_version() -> Result<()> {
+    let lua = Lua::new();
+    let jit: Table = lua.globals().get("jit")?;
+    assert!(jit
+        .get::<_, String>("version")?
+        .to_str()?
+        .contains("LuaJIT"));
+    Ok(())
+}

tests/thread.rs

@@ -100,7 +100,12 @@ fn coroutine_from_closure() -> Result<()> {
     let thrd_main = lua.create_function(|_, ()| Ok(()))?;
     lua.globals().set("main", thrd_main)?;
 
-    #[cfg(any(feature = "lua53", feature = "lua52", feature = "luajit"))]
+    #[cfg(any(
+        feature = "lua54",
+        feature = "lua53",
+        feature = "lua52",
+        feature = "luajit"
+    ))]
     let thrd: Thread = lua.load("coroutine.create(main)").eval()?;
     #[cfg(feature = "lua51")]
     let thrd: Thread = lua

tests/userdata.rs

@@ -1,4 +1,7 @@
-use std::rc::Rc;
+use std::sync::Arc;
+
+#[cfg(feature = "lua54")]
+use std::sync::atomic::{AtomicI64, Ordering};
 
 use mlua::{
     AnyUserData, ExternalError, Function, Lua, MetaMethod, Result, String, UserData,
@@ -10,8 +13,8 @@ fn test_user_data() -> Result<()> {
     struct UserData1(i64);
     struct UserData2(Box<i64>);
 
-    impl UserData for UserData1 {};
-    impl UserData for UserData2 {};
+    impl UserData for UserData1 {}
+    impl UserData for UserData2 {}
 
     let lua = Lua::new();
     let userdata1 = lua.create_userdata(UserData1(1))?;
@@ -95,7 +98,7 @@ fn test_metamethods() -> Result<()> {
                     Err("no such custom index".to_lua_err())
                 }
             });
-            #[cfg(any(feature = "lua53", feature = "lua52"))]
+            #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
             methods.add_meta_method(MetaMethod::Pairs, |lua, data, ()| {
                 use std::iter::FromIterator;
                 let stateless_iter = lua.create_function(|_, (data, i): (MyUserData, i64)| {
@@ -120,7 +123,7 @@ fn test_metamethods() -> Result<()> {
         10
     );
 
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     let pairs_it = {
         lua.load(
             r#"
@@ -140,7 +143,7 @@ fn test_metamethods() -> Result<()> {
     assert_eq!(lua.load("userdata1 - userdata2").eval::<MyUserData>()?.0, 4);
     assert_eq!(lua.load("userdata1:get()").eval::<i64>()?, 7);
     assert_eq!(lua.load("userdata2.inner").eval::<i64>()?, 3);
-    #[cfg(any(feature = "lua53", feature = "lua52"))]
+    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
     assert_eq!(pairs_it.call::<_, i64>(())?, 28);
     assert!(lua.load("userdata2.nonexist_field").eval::<()>().is_err());
 
@@ -151,6 +154,58 @@ fn test_metamethods() -> Result<()> {
     assert!(userdata2 != userdata3); // because references are differ
     assert!(userdata2.equals(userdata3)?);
 
+    let userdata1: AnyUserData = globals.get("userdata1")?;
+    assert!(userdata1.has_metamethod(MetaMethod::Add)?);
+    assert!(userdata1.has_metamethod(MetaMethod::Sub)?);
+    assert!(userdata1.has_metamethod(MetaMethod::Index)?);
+    assert!(!userdata1.has_metamethod(MetaMethod::Pow)?);
+
+    Ok(())
+}
+
+#[test]
+#[cfg(feature = "lua54")]
+fn test_metamethod_close() -> Result<()> {
+    #[derive(Clone)]
+    struct MyUserData(Arc<AtomicI64>);
+
+    impl UserData for MyUserData {
+        fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
+            methods.add_method("get", |_, data, ()| Ok(data.0.load(Ordering::Relaxed)));
+            methods.add_meta_method(MetaMethod::Close, |_, data, _err: Value| {
+                data.0.store(0, Ordering::Relaxed);
+                Ok(())
+            });
+        }
+    }
+
+    let lua = Lua::new();
+    let globals = lua.globals();
+
+    let ud = MyUserData(Arc::new(AtomicI64::new(-1)));
+    let ud2 = ud.clone();
+
+    globals.set(
+        "new_userdata",
+        lua.create_function(move |_lua, val: i64| {
+            let ud = ud2.clone();
+            ud.0.store(val, Ordering::Relaxed);
+            Ok(ud)
+        })?,
+    )?;
+
+    lua.load(
+        r#"
+        do
+            local ud <close> = new_userdata(7)
+            assert(ud:get() == 7)
+        end
+    "#,
+    )
+    .exec()?;
+
+    assert_eq!(ud.0.load(Ordering::Relaxed), 0);
+
     Ok(())
 }
 
@@ -196,22 +251,22 @@ fn test_gc_userdata() -> Result<()> {
 
 #[test]
 fn detroys_userdata() -> Result<()> {
-    struct MyUserdata(Rc<()>);
+    struct MyUserdata(Arc<()>);
 
     impl UserData for MyUserdata {}
 
-    let rc = Rc::new(());
+    let rc = Arc::new(());
 
     let lua = Lua::new();
     lua.globals().set("userdata", MyUserdata(rc.clone()))?;
 
-    assert_eq!(Rc::strong_count(&rc), 2);
+    assert_eq!(Arc::strong_count(&rc), 2);
 
     // should destroy all objects
     let _ = lua.globals().raw_remove("userdata")?;
     lua.gc_collect()?;
 
-    assert_eq!(Rc::strong_count(&rc), 1);
+    assert_eq!(Arc::strong_count(&rc), 1);
 
     Ok(())
 }