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

@@ -27,15 +27,78 @@ jobs:
     - name: Build ${{ matrix.lua }} vendored
       run: |
         cargo build --release --features "${{ matrix.lua }} vendored"
-        cargo build --release --features "${{ matrix.lua }} vendored async send"
+        cargo build --release --features "${{ matrix.lua }} vendored async send serialize"
       shell: bash
     - name: Build ${{ matrix.lua }} pkg-config
       if: ${{ matrix.os == 'ubuntu-18.04' && matrix.lua != 'lua54' }}
       run: |
-        sudo apt-get update -y
+        sudo apt-get update
         sudo apt-get install -y --no-install-recommends liblua5.3-dev liblua5.2-dev liblua5.1-0-dev libluajit-5.1-dev
         cargo build --release --features "${{ 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 "${{ matrix.lua }} async send serialize vendored"
+
+  build_aarch64_cross_ubuntu:
+    name: Cross-compile to aarch64-unknown-linux-gnu
+    runs-on: ubuntu-18.04
+    needs: build
+    strategy:
+      matrix:
+        lua: [lua54, lua53, lua52, lua51, luajit]
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: nightly
+        target: aarch64-unknown-linux-gnu
+        override: true
+    - name: Install ARM compiler toolchain
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y --no-install-recommends gcc-aarch64-linux-gnu libc6-dev-arm64-cross
+      shell: bash
+    - name: Cross-compile
+      run: cargo build --target aarch64-unknown-linux-gnu --features "${{ matrix.lua }} async send serialize vendored"
+      shell: bash
+
+  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@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
+        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:
     name: Test
     runs-on: ${{ matrix.os }}
@@ -60,41 +123,19 @@ jobs:
         target: ${{ matrix.target }}
         override: true
     - name: Run ${{ matrix.lua }} tests
-      if: ${{ matrix.os != 'macos-latest' || matrix.lua != 'luajit' }}
       run: |
         cargo test --release --features "${{ matrix.lua }} vendored"
-        cargo test --release --features "${{ matrix.lua }} vendored async send"
+        cargo test --release --features "${{ matrix.lua }} vendored async send serialize"
       shell: bash
-    - name: Run compile tests
-      if: ${{ matrix.os == 'ubuntu-18.04' && matrix.lua == 'lua53' }}
+    - name: Run compile tests (macos lua53)
+      if: ${{ matrix.os == 'macos-latest' && matrix.lua == 'lua53' }}
       run: |
-        cargo test --release --features "${{ matrix.lua }} vendored" -- --ignored
-        cargo test --release --features "${{ matrix.lua }} vendored async send" -- --ignored
-      shell: bash
-
-  test_luajit_macos:
-    name: Test LuaJIT on macOS
-    runs-on: macos-latest
-    needs: build
-    steps:
-    - uses: actions/checkout@v2
-    - uses: actions-rs/toolchain@v1
-      with:
-        toolchain: nightly
-        target: x86_64-apple-darwin
-        override: true
-    - name: Run LuaJIT 2.0.5 tests
-      run: |
-        brew install luajit pkg-config
-        cargo test --tests --release --features "luajit async send" -- --test-threads=1
-      shell: bash
-    - name: Run LuaJIT vendored tests
-      run: |
-        cargo test --release --features "luajit vendored async send"
+        TRYBUILD=overwrite cargo test --release --features "${{ matrix.lua }} vendored" -- --ignored
+        TRYBUILD=overwrite cargo test --release --features "${{ matrix.lua }} vendored async send serialize" -- --ignored
       shell: bash
 
   test_modules:
-    name: Test modules on Linux and macOS
+    name: Test modules
     runs-on: ${{ matrix.os }}
     needs: build
     strategy:
@@ -126,21 +167,16 @@ jobs:
     needs: build
     strategy:
       matrix:
-        lua: [lua53, lua51, luajit]
+        lua: [lua53, luajit]
     defaults:
       run:
-        shell: bash.exe --login -eo pipefail "{0}"
-    env:
-      MSYSTEM: MINGW64
-      CHERE_INVOKING: 1
+        shell: msys2 {0}
     steps:
+    - uses: msys2/setup-msys2@v2
     - uses: actions/checkout@v2
-    - name: Set up shell
-      run: echo ::add-path::C:\msys64\usr\bin\
-      shell: pwsh
     - name: Install Rust & Lua
       run: |
-        pacman -S --noconfirm mingw-w64-x86_64-rust mingw-w64-x86_64-lua mingw-w64-x86_64-lua51 mingw-w64-x86_64-luajit
+        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 }}")
@@ -174,4 +210,4 @@ jobs:
       - uses: actions-rs/clippy-check@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
-          args: --features "${{ matrix.lua }},async,send,vendored
+          args: --features "${{ matrix.lua }},vendored,async,send,serialize

CHANGELOG.md

@@ -1,3 +1,39 @@
+## 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`.

Cargo.toml

@@ -1,27 +1,24 @@
 [package]
 name = "mlua"
-version = "0.4.0"
+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 5.1/5.2/5.3/5.4 (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" }
-maintenance = { status = "actively-developed" }
-
 [package.metadata.docs.rs]
-features = ["async"]
+features = ["lua53", "async", "send", "serialize"]
+rustdoc-args = ["--cfg", "docsrs"]
 
 [workspace]
 members = [
@@ -37,41 +34,52 @@ lua52 = []
 lua51 = []
 luajit = []
 vendored = ["lua-src", "luajit-src"]
-module = []
+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 }
 lazy_static = { version = "1.4" }
-num-traits = { version = "0.2.11" }
+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 = "535.0.4", optional = true }
-luajit-src = { version = "210.1.0", 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 = "0.3.5"
-hyper = "0.13"
-tokio = { version = "0.2", features = ["full"] }
+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"]
@@ -79,3 +87,7 @@ required-features = ["async", "send"]
 [[example]]
 name = "async_tcp_server"
 required-features = ["async"]
+
+[[example]]
+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
@@ -7,35 +7,70 @@
 [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)
 
 `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 v0.15](https://github.com/amethyst/rlua/tree/0.15.3) fork, `mlua` supports *__all__* major Lua versions (including LuaJIT) and allows to write native Lua modules in Rust as well as use Lua in a standalone mode.
+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` supports the following Lua versions (and tested on Windows/macOS/Linux):
-- Lua 5.4 (`feature = "lua54"`)
-- Lua 5.3 (`feature = "lua53"`)
-- Lua 5.2 (`feature = "lua52"`)
-- Lua 5.1 (`feature = "lua51"`)
-- LuaJIT 2.1.0 beta (`feature = "luajit"`)
-- LuaJIT 2.0.5 stable (`feature = "luajit"`)
+`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).
 
-Additional `feature = "vendored"` enables building static Lua from sources during `mlua` compilation.
+[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 v0.3, `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 `feature = "async"` 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)
 
+### Serialization (serde) support
+
+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).
+
+[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.
@@ -55,11 +90,13 @@ my_project $ LUA_INC=$HOME/tmp/lua-5.2.4/src LUA_LIB=$HOME/tmp/lua-5.2.4/src LUA
 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 = { version = "0.4", features = ["lua53"] }
+mlua = { version = "0.5", features = ["lua53", "vendored"] }
 ```
 
 `main.rs`
@@ -83,6 +120,7 @@ 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)
 
@@ -93,15 +131,12 @@ Add to `Cargo.toml` :
 crate-type = ["cdylib"]
 
 [dependencies]
-mlua = { version = "0.4", features = ["lua53", "module"] }
-mlua_derive = "0.4"
+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<()> {
@@ -109,7 +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)?)?;
@@ -133,11 +168,17 @@ 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 is not supported since you need to link to a Lua dll.
+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.
 

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_normal.rs

@@ -1,13 +1,19 @@
 use std::env;
-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_default();
-    let lib_dir = env::var_os("LUA_LIB").unwrap_or_default();
-    let lua_lib = env::var_os("LUA_LIB_NAME").unwrap_or_default();
+    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");
@@ -16,11 +22,22 @@ pub fn probe_lua() -> PathBuf {
 
     let need_lua_lib = cfg!(any(not(feature = "module"), target_os = "windows"));
 
-    if include_dir != "" && (!need_lua_lib || lib_dir != "") {
-        if lua_lib == "" {
-            panic!("LUA_LIB_NAME is not set");
+    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);
         }
-        let _version = use_custom_lua(&include_dir, &lib_dir, &lua_lib).unwrap();
         return PathBuf::from(include_dir);
     }
 
@@ -100,39 +117,3 @@ pub fn probe_lua() -> PathBuf {
         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 link_lib = match env::var("LUA_LINK") {
-        Ok(s) if s == "static" => "static=",
-        _ => "",
-    };
-
-    if cfg!(any(not(feature = "module"), target_os = "windows")) {
-        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/main.rs

@@ -1,7 +1,8 @@
 #![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;
 
@@ -91,6 +92,105 @@ 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",
@@ -132,5 +232,12 @@ fn main() {
     );
 
     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

@@ -2,8 +2,9 @@ use std::collections::HashMap;
 use std::sync::Arc;
 
 use bstr::BString;
-use hyper::{body::Body as HyperBody, Client as HyperClient};
-use tokio::{stream::StreamExt, sync::Mutex};
+use hyper::body::{Body as HyperBody, HttpBody as _};
+use hyper::Client as HyperClient;
+use tokio::sync::Mutex;
 
 use mlua::{Error, Lua, Result, UserData, UserDataMethods};
 
@@ -20,8 +21,8 @@ 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.lock().await;
-            let bytes = reader.try_next().await.map_err(Error::external)?;
-            if let Some(bytes) = bytes {
+            if let Some(bytes) = reader.data().await {
+                let bytes = bytes.map_err(Error::external)?;
                 return Ok(Some(BString::from(bytes.as_ref())));
             }
             Ok(None)
@@ -61,7 +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_tcp_server.rs

@@ -1,9 +1,8 @@
-use std::net::Shutdown;
 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;
 
@@ -55,7 +54,7 @@ impl UserData for LuaTcpStream {
         });
 
         methods.add_async_method("close", |_, stream, ()| async move {
-            stream.0.lock().await.shutdown(Shutdown::Both)?;
+            stream.0.lock().await.shutdown().await?;
             Ok(())
         });
     }
@@ -63,7 +62,7 @@ impl UserData for LuaTcpStream {
 
 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(())
     })?;
 

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.toml

@@ -17,4 +17,3 @@ vendored = ["mlua/vendored"]
 
 [dependencies]
 mlua = { path = "../..", features = ["module"] }
-mlua_derive = { path = "../../mlua_derive" }

examples/module/src/lib.rs

@@ -8,7 +8,7 @@ fn used_memory(lua: &Lua, _: ()) -> LuaResult<usize> {
     Ok(lua.used_memory())
 }
 
-#[mlua_derive::lua_module]
+#[mlua::lua_module]
 fn rust_module(lua: &Lua) -> LuaResult<LuaTable> {
     let exports = lua.create_table()?;
     exports.set("sum", lua.create_function(sum)?)?;

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 = "0.4.0"
+version = "0.5.0"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 edition = "2018"
 description = "Procedural macros for the mlua crate."

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, MaybeSend, Number};
+use crate::types::{LightUserData, MaybeSend};
 use crate::userdata::{AnyUserData, UserData};
 use crate::value::{FromLua, Nil, ToLua, Value};
 
@@ -222,6 +223,12 @@ impl<'lua> ToLua<'lua> for &str {
     }
 }
 
+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())?))
@@ -256,6 +263,12 @@ impl<'lua> ToLua<'lua> for &CStr {
     }
 }
 
+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)?))
@@ -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)
             }
         }
 
@@ -481,6 +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

@@ -9,6 +9,7 @@ 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 {
@@ -105,6 +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
@@ -132,6 +140,19 @@ pub enum Error {
         /// Original error returned by the Rust code.
         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.
@@ -206,6 +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 => {
@@ -214,6 +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),
         }
     }
@@ -289,3 +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

src/ffi/glue/glue.c

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019-2020 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
@@ -225,12 +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))),
@@ -244,8 +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),

src/ffi/lauxlib.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019-2020 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

src/ffi/lua.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019-2020 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
@@ -32,13 +32,14 @@ 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};
 
+#[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;

src/ffi/luaconf.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019-2020 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
@@ -23,7 +23,6 @@
 
 //! 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;

src/ffi/lualib.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019-2020 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

src/ffi/mod.rs

@@ -1,6 +1,6 @@
 // The MIT License (MIT)
 //
-// Copyright (c) 2019-2020 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
@@ -211,8 +211,8 @@ 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(any(feature = "lua54", feature = "lua53"))]

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;
@@ -119,6 +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,
@@ -205,6 +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

@@ -37,7 +37,7 @@ impl<'a> Debug<'a> {
         }
     }
 
-    /// Corresponds to the `n` what mask.
+    /// Corresponds to the `S` what mask.
     pub fn source(&self) -> DebugSource<'a> {
         unsafe {
             mlua_assert!(

src/lib.rs

@@ -24,6 +24,18 @@
 //! 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`].
@@ -34,7 +46,7 @@
 //!
 //! # `Send` requirement
 //! By default `mlua` is `!Send`. This can be changed by enabling `feature = "send"` that adds `Send` requirement
-//! to `Function`s and [`UserData`].
+//! to [`Function`]s and [`UserData`].
 //!
 //! [Lua programming language]: https://www.lua.org/
 //! [`Lua`]: struct.Lua.html
@@ -45,16 +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;
@@ -81,7 +101,7 @@ pub use crate::ffi::lua_State;
 pub use crate::error::{Error, ExternalError, ExternalResult, Result};
 pub use crate::function::Function;
 pub use crate::hook::{Debug, DebugNames, DebugSource, DebugStack, HookTriggers};
-pub use crate::lua::{Chunk, GCMode, Lua};
+pub use crate::lua::{Chunk, ChunkMode, GCMode, Lua};
 pub use crate::multi::Variadic;
 pub use crate::scope::Scope;
 pub use crate::stdlib::StdLib;
@@ -95,4 +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/lua.rs

@@ -1,9 +1,10 @@
 use std::any::TypeId;
 use std::cell::{RefCell, UnsafeCell};
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::ffi::CString;
 use std::marker::PhantomData;
 use std::os::raw::{c_char, c_int, c_void};
+use std::panic::resume_unwind;
 use std::sync::{Arc, Mutex, Weak};
 use std::{mem, ptr, str};
 
@@ -18,13 +19,14 @@ use crate::table::Table;
 use crate::thread::Thread;
 use crate::types::{
     Callback, HookCallback, Integer, LightUserData, LuaRef, MaybeSend, Number, RegistryKey,
+    UserDataCell,
 };
-use crate::userdata::{AnyUserData, MetaMethod, UserData, UserDataMethods};
+use crate::userdata::{AnyUserData, MetaMethod, UserData, UserDataMethods, UserDataWrapped};
 use crate::util::{
-    assert_stack, callback_error, check_stack, get_gc_userdata, get_main_state,
-    get_meta_gc_userdata, get_wrapped_error, init_error_registry, init_gc_metatable_for,
-    init_userdata_metatable, pop_error, protect_lua, protect_lua_closure, push_gc_userdata,
-    push_meta_gc_userdata, push_string, push_userdata, push_wrapped_error, StackGuard,
+    assert_stack, callback_error, check_stack, get_gc_userdata, get_main_state, get_userdata,
+    get_wrapped_error, init_error_registry, init_gc_metatable_for, init_userdata_metatable,
+    pop_error, protect_lua, protect_lua_closure, push_gc_userdata, push_meta_gc_userdata,
+    push_string, push_userdata, push_wrapped_error, StackGuard, WrappedPanic,
 };
 use crate::value::{FromLua, FromLuaMulti, MultiValue, Nil, ToLua, ToLuaMulti, Value};
 
@@ -39,6 +41,9 @@ use {
     futures_util::future::{self, TryFutureExt},
 };
 
+#[cfg(feature = "serialize")]
+use {crate::util::get_destructed_userdata_metatable, serde::Serialize};
+
 /// Top level Lua struct which holds the Lua state itself.
 pub struct Lua {
     pub(crate) state: *mut ffi::lua_State,
@@ -53,8 +58,10 @@ pub struct Lua {
 // Data associated with the lua_State.
 struct ExtraData {
     registered_userdata: HashMap<TypeId, c_int>,
+    registered_userdata_mt: HashSet<isize>,
     registry_unref_list: Arc<Mutex<Option<Vec<c_int>>>>,
 
+    libs: StdLib,
     mem_info: *mut MemoryInfo,
 
     ref_thread: *mut ffi::lua_State,
@@ -94,19 +101,22 @@ pub(crate) static EXTRA_REGISTRY_KEY: u8 = 0;
 
 /// Requires `feature = "send"`
 #[cfg(feature = "send")]
+#[cfg_attr(docsrs, doc(cfg(feature = "send")))]
 unsafe impl Send for Lua {}
 
 impl Drop for Lua {
     fn drop(&mut self) {
         unsafe {
             if !self.ephemeral {
-                let mut extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
+                let extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
                 mlua_debug_assert!(
                     ffi::lua_gettop(extra.ref_thread) == extra.ref_stack_max
                         && extra.ref_stack_max as usize == extra.ref_free.len(),
                     "reference leak detected"
                 );
-                *mlua_expect!(extra.registry_unref_list.lock(), "unref list poisoned") = None;
+                let mut unref_list =
+                    mlua_expect!(extra.registry_unref_list.lock(), "unref list poisoned");
+                *unref_list = None;
                 ffi::lua_close(self.main_state.expect("main_state is null"));
                 if !extra.mem_info.is_null() {
                     Box::from_raw(extra.mem_info);
@@ -164,7 +174,9 @@ impl Lua {
 
         let mut lua = unsafe { Self::unsafe_new_with(libs) };
 
-        mlua_expect!(lua.disable_c_modules(), "Error during disabling C modules");
+        if libs.contains(StdLib::PACKAGE) {
+            mlua_expect!(lua.disable_c_modules(), "Error during disabling C modules");
+        }
         lua.safe = true;
 
         Ok(lua)
@@ -254,7 +266,7 @@ impl Lua {
         lua.ephemeral = false;
         #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
         {
-            lua.extra.lock().unwrap().mem_info = mem_info;
+            mlua_expect!(lua.extra.lock(), "extra is poisoned").mem_info = mem_info;
         }
 
         mlua_expect!(
@@ -263,6 +275,7 @@ impl Lua {
             }),
             "Error during loading standard libraries"
         );
+        mlua_expect!(lua.extra.lock(), "extra is poisoned").libs |= libs;
 
         lua
     }
@@ -292,6 +305,10 @@ impl Lua {
                     init_gc_metatable_for::<Waker>(state, None);
                 }
 
+                // Init serde metatables
+                #[cfg(feature = "serialize")]
+                crate::serde::init_metatables(state);
+
                 // Create ref stack thread and place it in the registry to prevent it from being garbage
                 // collected.
 
@@ -306,8 +323,10 @@ impl Lua {
 
         let extra = Arc::new(Mutex::new(ExtraData {
             registered_userdata: HashMap::new(),
+            registered_userdata_mt: HashSet::new(),
             registry_unref_list: Arc::new(Mutex::new(Some(Vec::new()))),
             ref_thread,
+            libs: StdLib::NONE,
             mem_info: ptr::null_mut(),
             // We need 1 extra stack space to move values in and out of the ref stack.
             ref_stack_size: ffi::LUA_MINSTACK - 1,
@@ -368,11 +387,20 @@ impl Lua {
         }
 
         let state = self.main_state.unwrap_or(self.state);
-        unsafe {
+        let res = unsafe {
             protect_lua_closure(state, 0, 0, |state| {
                 load_from_std_lib(state, libs);
             })
+        };
+
+        // If `package` library loaded into a safe lua state then disable C modules
+        let curr_libs = mlua_expect!(self.extra.lock(), "extra is poisoned").libs;
+        if self.safe && (curr_libs ^ (curr_libs | libs)).contains(StdLib::PACKAGE) {
+            mlua_expect!(self.disable_c_modules(), "Error during disabling C modules");
         }
+        mlua_expect!(self.extra.lock(), "extra is poisoned").libs |= libs;
+
+        res
     }
 
     /// Consumes and leaks `Lua` object, returning a static reference `&'static Lua`.
@@ -490,7 +518,7 @@ impl Lua {
         unsafe { (*extra.mem_info).used_memory as usize }
     }
 
-    /// Sets a memory limit on this Lua state.
+    /// Sets a memory limit (in bytes) on this Lua state.
     ///
     /// Once an allocation occurs that would pass this memory limit,
     /// a `Error::MemoryError` is generated instead.
@@ -658,6 +686,9 @@ impl Lua {
     /// similar on the returned builder.  Code is not even parsed until one of these methods is
     /// called.
     ///
+    /// If this `Lua` was created with `unsafe_new`, `load` will automatically detect and load
+    /// chunks of either text or binary type, as if passing `bt` mode to `luaL_loadbufferx`.
+    ///
     /// [`Chunk::exec`]: struct.Chunk.html#method.exec
     pub fn load<'lua, 'a, S>(&'lua self, source: &'a S) -> Chunk<'lua, 'a>
     where
@@ -668,6 +699,7 @@ impl Lua {
             source: source.as_ref(),
             name: None,
             env: None,
+            mode: None,
         }
     }
 
@@ -676,28 +708,35 @@ impl Lua {
         source: &[u8],
         name: Option<&CString>,
         env: Option<Value<'lua>>,
+        mode: Option<ChunkMode>,
     ) -> Result<Function<'lua>> {
         unsafe {
             let _sg = StackGuard::new(self.state);
             assert_stack(self.state, 1);
 
-            match if let Some(name) = name {
-                ffi::luaL_loadbufferx(
-                    self.state,
-                    source.as_ptr() as *const c_char,
-                    source.len(),
-                    name.as_ptr() as *const c_char,
-                    cstr!("t"),
-                )
-            } else {
-                ffi::luaL_loadbufferx(
-                    self.state,
-                    source.as_ptr() as *const c_char,
-                    source.len(),
-                    ptr::null(),
-                    cstr!("t"),
-                )
-            } {
+            let mode_str = match mode {
+                Some(ChunkMode::Binary) if self.safe => {
+                    return Err(Error::SafetyError(
+                        "binary chunks are disabled in safe mode".to_string(),
+                    ))
+                }
+                Some(ChunkMode::Binary) => cstr!("b"),
+                Some(ChunkMode::Text) => cstr!("t"),
+                None if source.starts_with(ffi::LUA_SIGNATURE) && self.safe => {
+                    return Err(Error::SafetyError(
+                        "binary chunks are disabled in safe mode".to_string(),
+                    ))
+                }
+                None => cstr!("bt"),
+            };
+
+            match ffi::luaL_loadbufferx(
+                self.state,
+                source.as_ptr() as *const c_char,
+                source.len(),
+                name.map(|n| n.as_ptr()).unwrap_or_else(ptr::null),
+                mode_str,
+            ) {
                 ffi::LUA_OK => {
                     if let Some(env) = env {
                         self.push_value(env)?;
@@ -728,7 +767,7 @@ impl Lua {
         }
     }
 
-    /// Creates and returns a new table.
+    /// Creates and returns a new empty table.
     pub fn create_table(&self) -> Result<Table> {
         unsafe {
             let _sg = StackGuard::new(self.state);
@@ -742,6 +781,21 @@ impl Lua {
         }
     }
 
+    /// Creates and returns a new empty table, with the specified capacity.
+    /// `narr` is a hint for how many elements the table will have as a sequence;
+    /// `nrec` is a hint for how many other elements the table will have.
+    /// Lua may use these hints to preallocate memory for the new table.
+    pub fn create_table_with_capacity(&self, narr: c_int, nrec: c_int) -> Result<Table> {
+        unsafe {
+            let _sg = StackGuard::new(self.state);
+            assert_stack(self.state, 4);
+            protect_lua_closure(self.state, 0, 1, |state| {
+                ffi::lua_createtable(state, narr, nrec)
+            })?;
+            Ok(Table(self.pop_ref()))
+        }
+    }
+
     /// Creates a table and fills it with values from an iterator.
     pub fn create_table_from<'lua, K, V, I>(&'lua self, cont: I) -> Result<Table<'lua>>
     where
@@ -903,8 +957,9 @@ impl Lua {
     /// ```
     ///
     /// [`Thread`]: struct.Thread.html
-    /// [`ThreadStream`]: struct.ThreadStream.html
+    /// [`AsyncThread`]: struct.AsyncThread.html
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub fn create_async_function<'lua, 'callback, A, R, F, FR>(
         &'lua self,
         func: F,
@@ -947,7 +1002,19 @@ impl Lua {
     where
         T: 'static + MaybeSend + UserData,
     {
-        unsafe { self.make_userdata(data) }
+        unsafe { self.make_userdata(UserDataWrapped::new(data)) }
+    }
+
+    /// Create a Lua userdata object from a custom serializable userdata type.
+    ///
+    /// Requires `feature = "serialize"`
+    #[cfg(feature = "serialize")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
+    pub fn create_ser_userdata<T>(&self, data: T) -> Result<AnyUserData>
+    where
+        T: 'static + MaybeSend + UserData + Serialize,
+    {
+        unsafe { self.make_userdata(UserDataWrapped::new_ser(data)) }
     }
 
     /// Returns a handle to the global environment.
@@ -1008,6 +1075,7 @@ impl Lua {
     ///
     /// [`scope`]: #method.scope
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub fn async_scope<'lua, 'scope, R, F, FR>(
         &'lua self,
         f: F,
@@ -1274,11 +1342,10 @@ impl Lua {
     /// by `Lua::remove_registry_value`.
     pub fn expire_registry_values(&self) {
         unsafe {
-            let mut extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
-            let unref_list = mem::replace(
-                &mut *mlua_expect!(extra.registry_unref_list.lock(), "unref list poisoned"),
-                Some(Vec::new()),
-            );
+            let extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
+            let mut unref_list =
+                mlua_expect!(extra.registry_unref_list.lock(), "unref list poisoned");
+            let unref_list = mem::replace(&mut *unref_list, Some(Vec::new()));
             for id in mlua_expect!(unref_list, "unref list not set") {
                 ffi::luaL_unref(self.state, ffi::LUA_REGISTRYINDEX, id);
             }
@@ -1338,32 +1405,33 @@ impl Lua {
 
     // Uses 2 stack spaces, does not call checkstack
     pub(crate) unsafe fn pop_value(&self) -> Value {
-        match ffi::lua_type(self.state, -1) {
+        let state = self.state;
+        match ffi::lua_type(state, -1) {
             ffi::LUA_TNIL => {
-                ffi::lua_pop(self.state, 1);
+                ffi::lua_pop(state, 1);
                 Nil
             }
 
             ffi::LUA_TBOOLEAN => {
-                let b = Value::Boolean(ffi::lua_toboolean(self.state, -1) != 0);
-                ffi::lua_pop(self.state, 1);
+                let b = Value::Boolean(ffi::lua_toboolean(state, -1) != 0);
+                ffi::lua_pop(state, 1);
                 b
             }
 
             ffi::LUA_TLIGHTUSERDATA => {
-                let ud = Value::LightUserData(LightUserData(ffi::lua_touserdata(self.state, -1)));
-                ffi::lua_pop(self.state, 1);
+                let ud = Value::LightUserData(LightUserData(ffi::lua_touserdata(state, -1)));
+                ffi::lua_pop(state, 1);
                 ud
             }
 
             ffi::LUA_TNUMBER => {
-                if ffi::lua_isinteger(self.state, -1) != 0 {
-                    let i = Value::Integer(ffi::lua_tointeger(self.state, -1));
-                    ffi::lua_pop(self.state, 1);
+                if ffi::lua_isinteger(state, -1) != 0 {
+                    let i = Value::Integer(ffi::lua_tointeger(state, -1));
+                    ffi::lua_pop(state, 1);
                     i
                 } else {
-                    let n = Value::Number(ffi::lua_tonumber(self.state, -1));
-                    ffi::lua_pop(self.state, 1);
+                    let n = Value::Number(ffi::lua_tonumber(state, -1));
+                    ffi::lua_pop(state, 1);
                     n
                 }
             }
@@ -1375,12 +1443,20 @@ impl Lua {
             ffi::LUA_TFUNCTION => Value::Function(Function(self.pop_ref())),
 
             ffi::LUA_TUSERDATA => {
-                // It should not be possible to interact with userdata types other than custom
-                // UserData types OR a WrappedError.  WrappedPanic should not be here.
-                if let Some(err) = get_wrapped_error(self.state, -1).as_ref() {
+                // We must prevent interaction with userdata types other than UserData OR a WrappedError.
+                // WrappedPanics are automatically resumed.
+                if let Some(err) = get_wrapped_error(state, -1).as_ref() {
                     let err = err.clone();
-                    ffi::lua_pop(self.state, 1);
+                    ffi::lua_pop(state, 1);
                     Value::Error(err)
+                } else if let Some(panic) = get_gc_userdata::<WrappedPanic>(state, -1).as_mut() {
+                    if let Some(panic) = (*panic).0.take() {
+                        ffi::lua_pop(state, 1);
+                        resume_unwind(panic);
+                    }
+                    // Previously resumed panic?
+                    ffi::lua_pop(state, 1);
+                    Nil
                 } else {
                     Value::UserData(AnyUserData(self.pop_ref()))
                 }
@@ -1438,9 +1514,10 @@ impl Lua {
     }
 
     pub(crate) unsafe fn userdata_metatable<T: 'static + UserData>(&self) -> Result<c_int> {
+        let type_id = TypeId::of::<T>();
         if let Some(table_id) = mlua_expect!(self.extra.lock(), "extra is poisoned")
             .registered_userdata
-            .get(&TypeId::of::<T>())
+            .get(&type_id)
         {
             return Ok(*table_id);
         }
@@ -1469,7 +1546,7 @@ impl Lua {
         let no_methods = methods.methods.is_empty();
 
         if no_methods {
-            init_userdata_metatable::<RefCell<T>>(self.state, -1, None)?;
+            init_userdata_metatable::<UserDataCell<T>>(self.state, -1, None)?;
         } else {
             protect_lua_closure(self.state, 0, 1, |state| {
                 ffi::lua_newtable(state);
@@ -1490,21 +1567,58 @@ impl Lua {
                 })?;
             }
 
-            init_userdata_metatable::<RefCell<T>>(self.state, -2, Some(-1))?;
+            init_userdata_metatable::<UserDataCell<T>>(self.state, -2, Some(-1))?;
             ffi::lua_pop(self.state, 1);
         }
 
+        let ptr = ffi::lua_topointer(self.state, -1);
         let id = protect_lua_closure(self.state, 1, 0, |state| {
             ffi::luaL_ref(state, ffi::LUA_REGISTRYINDEX)
         })?;
 
-        mlua_expect!(self.extra.lock(), "extra is poisoned")
-            .registered_userdata
-            .insert(TypeId::of::<T>(), id);
+        let mut extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
+        extra.registered_userdata.insert(type_id, id);
+        extra.registered_userdata_mt.insert(ptr as isize);
 
         Ok(id)
     }
 
+    pub(crate) fn register_userdata_metatable(&self, id: isize) {
+        let mut extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
+        extra.registered_userdata_mt.insert(id);
+    }
+
+    pub(crate) fn deregister_userdata_metatable(&self, id: isize) {
+        let mut extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
+        extra.registered_userdata_mt.remove(&id);
+    }
+
+    // Pushes a LuaRef value onto the stack, checking that it's a registered
+    // and not destructed UserData.
+    // Uses 2 stack spaces, does not call checkstack
+    #[cfg(feature = "serialize")]
+    pub(crate) unsafe fn push_userdata_ref(&self, lref: &LuaRef) -> Result<()> {
+        self.push_ref(lref);
+        if ffi::lua_getmetatable(self.state, -1) == 0 {
+            return Err(Error::UserDataTypeMismatch);
+        }
+        // Check that userdata is registered
+        let ptr = ffi::lua_topointer(self.state, -1);
+        let extra = mlua_expect!(self.extra.lock(), "extra is poisoned");
+        if extra.registered_userdata_mt.contains(&(ptr as isize)) {
+            ffi::lua_pop(self.state, 1);
+            return Ok(());
+        }
+        // Maybe userdata was destructed?
+        get_destructed_userdata_metatable(self.state);
+        if ffi::lua_rawequal(self.state, -1, -2) != 0 {
+            ffi::lua_pop(self.state, 2);
+            return Err(Error::UserDataDestructed);
+        }
+        ffi::lua_pop(self.state, 2);
+        Err(Error::UserDataTypeMismatch)
+    }
+
     // Creates a Function out of a Callback containing a 'static Fn.  This is safe ONLY because the
     // Fn is 'static, otherwise it could capture 'callback arguments improperly.  Without ATCs, we
     // cannot easily deal with the "correct" callback type of:
@@ -1522,12 +1636,13 @@ impl Lua {
     {
         unsafe extern "C" fn call_callback(state: *mut ffi::lua_State) -> c_int {
             callback_error(state, |nargs| {
-                let func =
-                    get_meta_gc_userdata::<Callback, Callback>(state, ffi::lua_upvalueindex(1));
-                let lua = get_gc_userdata::<Lua>(state, ffi::lua_upvalueindex(2));
-                if func.is_null() || lua.is_null() {
+                if ffi::lua_type(state, ffi::lua_upvalueindex(1)) == ffi::LUA_TNIL
+                    || ffi::lua_type(state, ffi::lua_upvalueindex(2)) == ffi::LUA_TNIL
+                {
                     return Err(Error::CallbackDestructed);
                 }
+                let func = get_userdata::<Callback>(state, ffi::lua_upvalueindex(1));
+                let lua = get_userdata::<Lua>(state, ffi::lua_upvalueindex(2));
 
                 if nargs < ffi::LUA_MINSTACK {
                     check_stack(state, ffi::LUA_MINSTACK - nargs)?;
@@ -1578,18 +1693,22 @@ impl Lua {
         'lua: 'callback,
     {
         #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
-        self.load_from_std_lib(StdLib::COROUTINE)?;
+        {
+            let libs = mlua_expect!(self.extra.lock(), "extra is poisoned").libs;
+            if !libs.contains(StdLib::COROUTINE) {
+                self.load_from_std_lib(StdLib::COROUTINE)?;
+            }
+        }
 
         unsafe extern "C" fn call_callback(state: *mut ffi::lua_State) -> c_int {
             callback_error(state, |nargs| {
-                let func = get_meta_gc_userdata::<AsyncCallback, AsyncCallback>(
-                    state,
-                    ffi::lua_upvalueindex(1),
-                );
-                let lua = get_gc_userdata::<Lua>(state, ffi::lua_upvalueindex(2));
-                if func.is_null() || lua.is_null() {
+                if ffi::lua_type(state, ffi::lua_upvalueindex(1)) == ffi::LUA_TNIL
+                    || ffi::lua_type(state, ffi::lua_upvalueindex(2)) == ffi::LUA_TNIL
+                {
                     return Err(Error::CallbackDestructed);
                 }
+                let func = get_userdata::<AsyncCallback>(state, ffi::lua_upvalueindex(1));
+                let lua = get_userdata::<Lua>(state, ffi::lua_upvalueindex(2));
 
                 if nargs < ffi::LUA_MINSTACK {
                     check_stack(state, ffi::LUA_MINSTACK - nargs)?;
@@ -1616,14 +1735,16 @@ impl Lua {
 
         unsafe extern "C" fn poll_future(state: *mut ffi::lua_State) -> c_int {
             callback_error(state, |nargs| {
-                let fut = get_gc_userdata::<LocalBoxFuture<Result<MultiValue>>>(
+                if ffi::lua_type(state, ffi::lua_upvalueindex(1)) == ffi::LUA_TNIL
+                    || ffi::lua_type(state, ffi::lua_upvalueindex(2)) == ffi::LUA_TNIL
+                {
+                    return Err(Error::CallbackDestructed);
+                }
+                let fut = get_userdata::<LocalBoxFuture<Result<MultiValue>>>(
                     state,
                     ffi::lua_upvalueindex(1),
                 );
-                let lua = get_gc_userdata::<Lua>(state, ffi::lua_upvalueindex(2));
-                if fut.is_null() || lua.is_null() {
-                    return Err(Error::CallbackDestructed);
-                }
+                let lua = get_userdata::<Lua>(state, ffi::lua_upvalueindex(2));
 
                 if nargs < ffi::LUA_MINSTACK {
                     check_stack(state, ffi::LUA_MINSTACK - nargs)?;
@@ -1644,17 +1765,19 @@ impl Lua {
 
                 match (*fut).as_mut().poll(&mut ctx) {
                     Poll::Pending => {
-                        check_stack(state, 6)?;
+                        check_stack(state, 1)?;
                         ffi::lua_pushboolean(state, 0);
-                        push_gc_userdata(state, AsyncPollPending)?;
-                        Ok(2)
+                        Ok(1)
                     }
                     Poll::Ready(results) => {
-                        let results = lua.create_sequence_from(results?)?;
-                        check_stack(state, 2)?;
+                        let results = results?;
+                        let nresults = results.len() as Integer;
+                        let results = lua.create_sequence_from(results)?;
+                        check_stack(state, 3)?;
                         ffi::lua_pushboolean(state, 1);
                         lua.push_value(Value::Table(results))?;
-                        Ok(2)
+                        lua.push_value(Value::Integer(nresults))?;
+                        Ok(3)
                     }
                 }
             })
@@ -1681,22 +1804,31 @@ impl Lua {
         env.set("yield", coroutine.get::<_, Function>("yield")?)?;
         env.set(
             "unpack",
-            self.create_function(|_, tbl: Table| {
+            self.create_function(|_, (tbl, len): (Table, Integer)| {
                 Ok(MultiValue::from_vec(
-                    tbl.sequence_values().collect::<Result<Vec<Value>>>()?,
+                    tbl.raw_sequence_values_by_len(Some(len))
+                        .collect::<Result<Vec<Value>>>()?,
                 ))
             })?,
         )?;
+        env.set("pending", unsafe {
+            let _sg = StackGuard::new(self.state);
+            check_stack(self.state, 5)?;
+            push_gc_userdata(self.state, AsyncPollPending)?;
+            self.pop_value()
+        })?;
 
+        // We set `poll` variable in the env table to be able to destroy upvalues
         self.load(
             r#"
-            local poll = get_poll(...)
+            poll = get_poll(...)
+            local poll, pending, yield, unpack = poll, pending, yield, unpack
             while true do
-                ready, res = poll()
+                local ready, res, nres = poll()
                 if ready then
-                    return unpack(res)
+                    return unpack(res, nres)
                 end
-                yield(res)
+                yield(pending)
             end
             "#,
         )
@@ -1705,7 +1837,7 @@ impl Lua {
         .into_function()
     }
 
-    pub(crate) unsafe fn make_userdata<T>(&self, data: T) -> Result<AnyUserData>
+    pub(crate) unsafe fn make_userdata<T>(&self, data: UserDataWrapped<T>) -> Result<AnyUserData>
     where
         T: 'static + UserData,
     {
@@ -1713,7 +1845,7 @@ impl Lua {
         assert_stack(self.state, 4);
 
         let ud_index = self.userdata_metatable::<T>()?;
-        push_userdata::<RefCell<T>>(self.state, RefCell::new(data))?;
+        push_userdata::<UserDataCell<T>>(self.state, RefCell::new(data))?;
 
         ffi::lua_rawgeti(
             self.state,
@@ -1802,6 +1934,14 @@ pub struct Chunk<'lua, 'a> {
     source: &'a [u8],
     name: Option<CString>,
     env: Option<Value<'lua>>,
+    mode: Option<ChunkMode>,
+}
+
+/// Represents chunk mode (text or binary).
+#[derive(Clone, Copy)]
+pub enum ChunkMode {
+    Text,
+    Binary,
 }
 
 impl<'lua, 'a> Chunk<'lua, 'a> {
@@ -1833,6 +1973,17 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
         Ok(self)
     }
 
+    /// Sets whether the chunk is text or binary (autodetected by default).
+    ///
+    /// Lua does not check the consistency of binary chunks, therefore this mode is allowed only
+    /// for instances created with [`Lua::unsafe_new`].
+    ///
+    /// [`Lua::unsafe_new`]: struct.Lua.html#method.unsafe_new
+    pub fn set_mode(mut self, mode: ChunkMode) -> Chunk<'lua, 'a> {
+        self.mode = Some(mode);
+        self
+    }
+
     /// Execute this chunk of code.
     ///
     /// This is equivalent to calling the chunk function with no arguments and no return values.
@@ -1849,6 +2000,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     ///
     /// [`Chunk::exec`]: struct.Chunk.html#method.exec
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub fn exec_async<'fut>(self) -> LocalBoxFuture<'fut, Result<()>>
     where
         'lua: 'fut,
@@ -1862,13 +2014,17 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     /// the value that it evaluates to.  Otherwise, the chunk is interpreted as a block as normal,
     /// and this is equivalent to calling `exec`.
     pub fn eval<R: FromLuaMulti<'lua>>(self) -> Result<R> {
-        // First, try interpreting the lua as an expression by adding
+        // Bytecode is always interpreted as a statement.
+        // For source code, first try interpreting the lua as an expression by adding
         // "return", then as a statement.  This is the same thing the
         // actual lua repl does.
-        if let Ok(function) = self.lua.load_chunk(
+        if self.source.starts_with(ffi::LUA_SIGNATURE) {
+            self.call(())
+        } else if let Ok(function) = self.lua.load_chunk(
             &self.expression_source(),
             self.name.as_ref(),
             self.env.clone(),
+            self.mode,
         ) {
             function.call(())
         } else {
@@ -1884,15 +2040,19 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     ///
     /// [`Chunk::eval`]: struct.Chunk.html#method.eval
     #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
     pub fn eval_async<'fut, R>(self) -> LocalBoxFuture<'fut, Result<R>>
     where
         'lua: 'fut,
         R: FromLuaMulti<'lua> + 'fut,
     {
-        if let Ok(function) = self.lua.load_chunk(
+        if self.source.starts_with(ffi::LUA_SIGNATURE) {
+            self.call_async(())
+        } else if let Ok(function) = self.lua.load_chunk(
             &self.expression_source(),
             self.name.as_ref(),
             self.env.clone(),
+            self.mode,
         ) {
             function.call_async(())
         } else {
@@ -1915,6 +2075,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     ///
     /// [`Chunk::call`]: struct.Chunk.html#method.call
     #[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,
@@ -1932,7 +2093,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     /// This simply compiles the chunk without actually executing it.
     pub fn into_function(self) -> Result<Function<'lua>> {
         self.lua
-            .load_chunk(self.source, self.name.as_ref(), self.env)
+            .load_chunk(self.source, self.name.as_ref(), self.env, self.mode)
     }
 
     fn expression_source(&self) -> Vec<u8> {

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/scope.rs

@@ -1,16 +1,19 @@
 use std::any::Any;
-use std::cell::{Cell, RefCell};
+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};
-use crate::userdata::{AnyUserData, MetaMethod, UserData, UserDataMethods};
+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,
@@ -20,9 +23,8 @@ use crate::value::{FromLuaMulti, MultiValue, ToLuaMulti, Value};
 #[cfg(feature = "async")]
 use {
     crate::types::AsyncCallback,
-    futures_core::future::Future,
+    futures_core::future::{Future, LocalBoxFuture},
     futures_util::future::{self, TryFutureExt},
-    std::os::raw::c_char,
 };
 
 /// Constructed by the [`Lua::scope`] method, allows temporarily creating Lua userdata and
@@ -112,6 +114,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
     /// [`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,
@@ -143,6 +146,33 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
     /// [`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,
     {
@@ -156,7 +186,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
                 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::<RefCell<T>>(state))]
+                vec![Box::new(take_userdata::<UserDataCell<T>>(state))]
             }));
             Ok(u)
         }
@@ -189,7 +219,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
     where
         T: 'scope + UserData,
     {
-        let data = Rc::new(RefCell::new(data));
+        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
@@ -198,7 +228,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
         // parameters.
         fn wrap_method<'scope, 'lua, 'callback: 'scope, T: 'scope>(
             scope: &Scope<'lua, 'scope>,
-            data: Rc<RefCell<T>>,
+            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
@@ -210,20 +240,18 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
             // first argument).
             let check_data = data.clone();
             let check_ud_type = move |lua: &'callback Lua, value| {
-                if let Some(value) = value {
-                    if let Value::UserData(u) = value {
-                        unsafe {
-                            assert_stack(lua.state, 1);
-                            lua.push_ref(&u.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;
+                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;
                     }
                 }
 
@@ -236,7 +264,10 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
                         if !check_ud_type(lua, args.pop_front()) {
                             return Err(Error::UserDataTypeMismatch);
                         }
-                        let data = data.try_borrow().map_err(|_| Error::UserDataBorrowError)?;
+                        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) }
@@ -252,6 +283,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
                             .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)
                     });
@@ -280,7 +312,8 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
             let _sg = StackGuard::new(lua.state);
             assert_stack(lua.state, 6);
 
-            push_userdata(lua.state, ())?;
+            // 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"))]
@@ -323,9 +356,22 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
                 ffi::lua_pop(lua.state, 1);
             }
 
+            let mt_id = ffi::lua_topointer(lua.state, -1);
             ffi::lua_setmetatable(lua.state, -2);
 
-            Ok(AnyUserData(lua.pop_ref()))
+            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)
         }
     }
 
@@ -387,12 +433,11 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
             #[cfg(any(feature = "lua51", feature = "luajit"))]
             ffi::lua_getfenv(state, -1);
 
-            // Then, get the get_poll() closure using the corresponding key
-            let key = "get_poll";
-            ffi::lua_pushlstring(state, key.as_ptr() as *const c_char, key.len());
+            // Second, get the `get_poll()` closure using the corresponding key
+            ffi::lua_pushstring(state, cstr!("get_poll"));
             ffi::lua_rawget(state, -2);
 
-            // Finally, destroy all upvalues
+            // Destroy all upvalues
             ffi::lua_getupvalue(state, -1, 1);
             let ud1 = take_userdata::<AsyncCallback>(state);
             ffi::lua_pushnil(state);
@@ -404,8 +449,25 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
             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)];
 
-            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)

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

@@ -47,6 +47,8 @@ impl StdLib {
     /// (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);
     /// The safe subset of the standard libraries

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;
@@ -447,9 +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> {
@@ -500,6 +553,7 @@ pub trait TableExt<'lua> {
     ///
     /// 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,
@@ -514,6 +568,7 @@ pub trait TableExt<'lua> {
     ///
     /// 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,
@@ -580,6 +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.
@@ -651,6 +731,8 @@ where
 pub struct TableSequence<'lua, V> {
     table: LuaRef<'lua>,
     index: Option<Integer>,
+    len: Option<Integer>,
+    raw: bool,
     _phantom: PhantomData<V>,
 }
 
@@ -669,9 +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

@@ -52,6 +52,7 @@ pub struct Thread<'lua>(pub(crate) LuaRef<'lua>);
 /// [`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>,
@@ -218,6 +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

@@ -10,6 +10,7 @@ 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;
 
@@ -31,6 +32,8 @@ pub(crate) type AsyncCallback<'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")]

src/userdata.rs

@@ -1,15 +1,21 @@
-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, MaybeSend};
-use crate::util::{assert_stack, get_userdata, StackGuard};
+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.
@@ -185,6 +191,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
     ///
     /// [`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,
@@ -231,6 +238,7 @@ pub trait UserDataMethods<'lua, T: UserData> {
     ///
     /// [`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,
@@ -360,6 +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`]
@@ -382,7 +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!(),
@@ -396,7 +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`.
@@ -407,9 +483,10 @@ 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 }))
         })
     }
 
@@ -515,7 +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;
@@ -534,9 +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))
                 }
             }
         }
@@ -555,3 +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

@@ -186,7 +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();
@@ -279,15 +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 {
@@ -591,27 +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?
@@ -725,7 +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.
@@ -759,7 +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.

tests/async.rs

@@ -1,15 +1,4 @@
 #![cfg(feature = "async")]
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
 
 use std::cell::Cell;
 use std::rc::Rc;
@@ -22,7 +11,9 @@ 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<()> {
@@ -134,6 +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();
@@ -332,11 +341,18 @@ async fn test_async_scope() -> Result<()> {
         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()
@@ -351,6 +367,14 @@ async fn test_async_scope() -> Result<()> {
         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(())
 }
 

tests/byte_string.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use bstr::{BStr, BString};
 use mlua::{Lua, Result};
 

tests/compile/async_nonstatic_userdata.stderr

@@ -22,14 +22,14 @@ note: ...so that the types are compatible
 13 | |                 Ok(())
 14 | |             });
    | |_____________^
-   = note: expected  `main::MyUserData<'_>`
-              found  `main::MyUserData<'a>`
+   = 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 std::future::Future` will meet its required lifetime bounds
+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

@@ -1,11 +1,16 @@
-error[E0277]: the type `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+error[E0277]: the type `UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
    --> $DIR/lua_norefunwindsafe.rs:7:5
     |
 7   |     catch_unwind(|| lua.create_table().unwrap());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+    |     ^^^^^^^^^^^^ `UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
     |
-    = help: within `mlua::lua::Lua`, the trait `std::panic::RefUnwindSafe` is not implemented for `std::cell::UnsafeCell<()>`
-    = note: required because it appears within the type `std::marker::PhantomData<std::cell::UnsafeCell<()>>`
-    = note: required because it appears within the type `mlua::lua::Lua`
-    = note: required because of the requirements on the impl of `std::panic::UnwindSafe` for `&mlua::lua::Lua`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile/lua_norefunwindsafe.rs:7:18: 7:48 lua:&mlua::lua::Lua]`
+   ::: $RUST/std/src/panic.rs
+    |
+    | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+    |                                        ---------- required by this bound in `catch_unwind`
+    |
+    = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<()>`
+    = note: required because it appears within the type `PhantomData<UnsafeCell<()>>`
+    = note: required because it appears within the type `Lua`
+    = note: required because of the requirements on the impl of `UnwindSafe` for `&Lua`
+    = note: required because it appears within the type `[closure@$DIR/tests/compile/lua_norefunwindsafe.rs:7:18: 7:48]`

tests/compile/non_send.stderr

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

@@ -1,13 +1,18 @@
-error[E0277]: the type `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+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());
-    |     ^^^^^^^^^^^^ `std::cell::UnsafeCell<()>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+    |     ^^^^^^^^^^^^ `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`
+   ::: $RUST/std/src/panic.rs
+    |
+    | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
+    |                                        ---------- required by this bound in `catch_unwind`
+    |
+    = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<()>`
+    = note: required because it appears within the type `PhantomData<UnsafeCell<()>>`
+    = note: required because it appears within the type `Lua`
+    = note: required because of the requirements on the impl of `UnwindSafe` for `&Lua`
     = note: required because it appears within the type `mlua::types::LuaRef<'_>`
-    = note: required because it appears within the type `mlua::table::Table<'_>`
-    = note: required because it appears within the type `[closure@$DIR/tests/compile/ref_nounwindsafe.rs:8:18: 8:54 table:mlua::table::Table<'_>]`
+    = 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.stderr

@@ -1,45 +1,26 @@
-error[E0495]: cannot infer an appropriate lifetime for autoref due to conflicting requirements
-  --> $DIR/scope_callback_capture.rs:8:14
-   |
-8  |             .create_function_mut(move |_, t: Table| {
-   |              ^^^^^^^^^^^^^^^^^^^
-   |
-note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the body at 5:15...
-  --> $DIR/scope_callback_capture.rs:5:15
-   |
-5  |       lua.scope(|scope| {
-   |  _______________^
-6  | |         let mut inner: Option<Table> = None;
-7  | |         let f = scope
-8  | |             .create_function_mut(move |_, t: Table| {
-...  |
-16 | |         Ok(())
-17 | |     });
-   | |_____^
-note: ...so that reference does not outlive borrowed content
+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
    |
-7  |         let f = scope
-   |                 ^^^^^
-note: but, the lifetime must be valid for the method call at 5:5...
-  --> $DIR/scope_callback_capture.rs:5:5
-   |
-5  | /     lua.scope(|scope| {
-6  | |         let mut inner: Option<Table> = None;
-7  | |         let f = scope
+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`.
 ...  |
-16 | |         Ok(())
-17 | |     });
-   | |______^
-note: ...so that a type/lifetime parameter is in scope here
-  --> $DIR/scope_callback_capture.rs:5:5
-   |
-5  | /     lua.scope(|scope| {
-6  | |         let mut inner: Option<Table> = None;
-7  | |         let f = scope
-8  | |             .create_function_mut(move |_, t: Table| {
-...  |
-16 | |         Ok(())
-17 | |     });
-   | |______^
+13 | |                 Ok(())
+14 | |             })?;
+   | |______________^ `scope` escapes the closure body here

tests/compile/scope_callback_inner.stderr

@@ -1,45 +1,42 @@
-error[E0495]: cannot infer an appropriate lifetime for autoref due to conflicting requirements
-  --> $DIR/scope_callback_inner.rs:8:14
-   |
-8  |             .create_function_mut(|_, t: Table| {
-   |              ^^^^^^^^^^^^^^^^^^^
-   |
-note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the body at 5:15...
-  --> $DIR/scope_callback_inner.rs:5:15
-   |
-5  |       lua.scope(|scope| {
-   |  _______________^
-6  | |         let mut inner: Option<Table> = None;
-7  | |         let f = scope
-8  | |             .create_function_mut(|_, t: Table| {
-...  |
-13 | |         Ok(())
-14 | |     });
-   | |_____^
-note: ...so that reference does not outlive borrowed content
+error[E0521]: borrowed data escapes outside of closure
   --> $DIR/scope_callback_inner.rs:7:17
    |
-7  |         let f = scope
-   |                 ^^^^^
-note: but, the lifetime must be valid for the method call at 5:5...
-  --> $DIR/scope_callback_inner.rs:5:5
-   |
-5  | /     lua.scope(|scope| {
-6  | |         let mut inner: Option<Table> = None;
-7  | |         let f = scope
+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| {
-...  |
-13 | |         Ok(())
-14 | |     });
-   | |______^
-note: ...so that a type/lifetime parameter is in scope here
-  --> $DIR/scope_callback_inner.rs:5:5
+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| {
-6  | |         let mut inner: Option<Table> = None;
-7  | |         let f = scope
+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| {
-...  |
-13 | |         Ok(())
-14 | |     });
-   | |______^
+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.stderr

@@ -1,11 +1,30 @@
-error: borrowed data cannot be stored outside of its closure
- --> $DIR/scope_callback_outer.rs:7:17
-  |
-5 |     let mut outer: Option<Table> = None;
-  |         --------- ...so that variable is valid at time of its declaration
-6 |     lua.scope(|scope| {
-  |               ------- borrowed data cannot outlive this closure
-7 |         let f = scope
-  |                 ^^^^^ cannot be stored outside of its closure
-8 |             .create_function_mut(|_, t: Table| {
-  |              ------------------- cannot infer an appropriate lifetime...
+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.stderr

@@ -2,7 +2,7 @@ error[E0373]: closure may outlive the current function, but it borrows `test`, w
   --> $DIR/scope_invariance.rs:14:38
    |
 9  |     lua.scope(|scope| {
-   |                ----- has type `&mlua::scope::Scope<'_, '1>`
+   |                ----- has type `&Scope<'_, '1>`
 ...
 14 |                 .create_function_mut(|_, ()| {
    |                                      ^^^^^^^ may outlive borrowed value `test`

tests/compile/scope_userdata_borrow.stderr

@@ -2,7 +2,7 @@ error[E0597]: `ibad` does not live long enough
   --> $DIR/scope_userdata_borrow.rs:15:56
    |
 11 |     lua.scope(|scope| {
-   |                ----- has type `&mlua::scope::Scope<'_, '1>`
+   |                ----- has type `&Scope<'_, '1>`
 ...
 15 |             scope.create_nonstatic_userdata(MyUserData(&ibad)).unwrap();
    |             -------------------------------------------^^^^^--

tests/function.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use mlua::{Function, Lua, Result, String};
 
 #[test]
@@ -87,3 +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

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::cell::RefCell;
 use std::ops::Deref;
 use std::str;

tests/memory.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::sync::Arc;
 
 use mlua::{Lua, Result, UserData};

tests/scope.rs

@@ -1,19 +1,9 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::cell::Cell;
 use std::rc::Rc;
 
-use mlua::{Error, Function, Lua, MetaMethod, Result, String, UserData, UserDataMethods};
+use mlua::{
+    AnyUserData, Error, Function, Lua, MetaMethod, Result, String, UserData, UserDataMethods,
+};
 
 #[test]
 fn scope_func() -> Result<()> {
@@ -57,17 +47,62 @@ fn scope_drop() -> Result<()> {
 
     lua.scope(|scope| {
         lua.globals()
-            .set("test", scope.create_userdata(MyUserdata(rc.clone()))?)?;
+            .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("test:method()").exec() {
-        Err(Error::CallbackError { .. }) => {}
+    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(())
 }
 

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/string.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::borrow::Cow;
 
 use mlua::{Lua, Result, String};

tests/table.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use mlua::{Lua, Nil, Result, Table, TableExt, Value};
 
 #[test]

tests/tests.rs

@@ -1,23 +1,11 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::iter::FromIterator;
-use std::panic::catch_unwind;
+use std::panic::{catch_unwind, AssertUnwindSafe};
 use std::sync::Arc;
 use std::{error, f32, f64, fmt};
 
 use mlua::{
-    Error, ExternalError, Function, Lua, Nil, Result, StdLib, String, Table, UserData, Value,
-    Variadic,
+    ChunkMode, Error, ExternalError, Function, Lua, Nil, Result, StdLib, String, Table, UserData,
+    Value, Variadic,
 };
 
 #[test]
@@ -56,6 +44,37 @@ fn test_safety() -> Result<()> {
         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(())
 }
 
@@ -127,6 +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();
@@ -318,62 +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(())
 }
@@ -457,7 +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);
 

tests/thread.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::panic::catch_unwind;
 
 use mlua::{Error, Function, Lua, Result, Thread, ThreadStatus};

tests/types.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::os::raw::c_void;
 
 use mlua::{Function, LightUserData, Lua, Result};

tests/userdata.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use std::sync::Arc;
 
 #[cfg(feature = "lua54")]
@@ -25,8 +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))?;

tests/value.rs

@@ -1,15 +1,3 @@
-#![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",
-    allow(unused_attributes)
-)]
-extern "system" {}
-
 use mlua::{Lua, Result, Value};
 
 #[test]