v0.9.0-beta.3

Plus `UserDataFields::add_meta_field()` for static meta fields.
Fix propagating fields to wrapped UserData types.

.github/workflows/coverage.yml

@@ -14,7 +14,7 @@ jobs:
 
       - name: Generate coverage report
         run: |
-          cargo tarpaulin --verbose --features lua54,vendored,async,send,serialize,macros --out xml --exclude-files benches --exclude-files build --exclude-files mlua_derive --exclude-files src/ffi --exclude-files tests
+          cargo tarpaulin --out xml --tests --exclude-files benches/* --exclude-files mlua-sys/src/*/*
 
       - name: Upload report to codecov.io
         uses: codecov/codecov-action@v3

.github/workflows/main.yml

@@ -9,7 +9,7 @@ jobs:
       matrix:
         os: [ubuntu-22.04, macos-latest, windows-latest]
         rust: [stable]
-        lua: [lua54, lua53, lua52, lua51, luajit, luau]
+        lua: [lua54, lua53, lua52, lua51, luajit, luau, luau-jit]
         include:
           - os: ubuntu-22.04
             target: x86_64-unknown-linux-gnu
@@ -104,7 +104,7 @@ jobs:
       matrix:
         os: [ubuntu-22.04, macos-latest, windows-latest]
         rust: [stable, nightly]
-        lua: [lua54, lua53, lua52, lua51, luajit, luajit52, luau]
+        lua: [lua54, lua53, lua52, lua51, luajit, luajit52, luau, luau-jit]
         include:
           - os: ubuntu-22.04
             target: x86_64-unknown-linux-gnu
@@ -118,11 +118,12 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} tests
         run: |
           cargo test --features "${{ matrix.lua }},vendored"
-          cargo test --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable"
+          cargo test --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot"
+          cargo test --features "${{ matrix.lua }},vendored,async,serialize,macros,parking_lot,unstable"
         shell: bash
       - name: Run compile tests (macos lua54)
         if: ${{ matrix.os == 'macos-latest' && matrix.lua == 'lua54' }}
@@ -139,7 +140,7 @@ jobs:
       matrix:
         os: [ubuntu-22.04]
         rust: [nightly]
-        lua: [lua54, lua53, lua52, lua51, luajit, luau]
+        lua: [lua54, lua53, lua52, lua51, luajit, luau, luau-jit]
         include:
           - os: ubuntu-22.04
             target: x86_64-unknown-linux-gnu
@@ -149,12 +150,13 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} tests with address sanitizer
         run: |
-          RUSTFLAGS="-Z sanitizer=address" \
             cargo test --tests --features "${{ matrix.lua }},vendored,async,send,serialize,macros,parking_lot,unstable" --target x86_64-unknown-linux-gnu -- --skip test_too_many_recursions
         shell: bash
+        env:
+          RUSTFLAGS: -Z sanitizer=address
 
   test_modules:
     name: Test modules
@@ -176,7 +178,7 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
           target: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v1
+      - uses: Swatinem/rust-cache@v2
       - name: Run ${{ matrix.lua }} module tests
         run: |
           (cd tests/module && cargo build --release --features "${{ matrix.lua }}")
@@ -220,7 +222,7 @@ jobs:
     runs-on: ubuntu-22.04
     strategy:
       matrix:
-        lua: [lua54, lua53, lua52, lua51, luajit, luau]
+        lua: [lua54, lua53, lua52, lua51, luajit, luau, luau-jit]
     steps:
       - uses: actions/checkout@v3
       - uses: dtolnay/rust-toolchain@stable

.gitignore

@@ -4,3 +4,4 @@ Cargo.lock
 
 .vscode/
 .DS_Store
+.stignore

CHANGELOG.md

@@ -1,3 +1,32 @@
+## v0.9.0-beta.3
+
+- Added `OwnedAnyUserData::take()`
+- Switch to `DeserializeOwned`
+- Overwrite error context when called multiple times
+- New feature flag `luau-jit` to enable (experimental) Luau codegen backend
+- Set `__name` field in userdata metatable
+- Added `Value::to_string()` method similar to `luaL_tolstring`
+- Lua 5.4.6
+- Application data container now allows to mutably and immutably borrow different types at the same time
+- Performance optimizations
+- Support getting and setting environment for Lua functions.
+- Added `UserDataFields::add_field()` method to add static fields to UserData
+
+Breaking changes:
+- Require environment to be a `Table` instead of `Value` in Chunks.
+- `AsChunk::env()` renamed to `AsChunk::environment()`
+
+## v0.9.0-beta.2
+
+New features:
+- Added `Thread::set_hook()` function to set hook on threads
+- Added pretty print to the Debug formatting to Lua `Value` and `Table`
+- ffi layer moved to `mlua-sys` crate
+- Added OwnedString (unstable)
+
+Breaking changes:
+- Refactor `HookTriggers` (make it const)
+
 ## v0.9.0-beta.1
 
 New features:

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua"
-version = "0.9.0-beta.1" # remember to update html_root_url and mlua_derive
+version = "0.9.0-beta.3" # remember to update mlua_derive
 authors = ["Aleksandr Orlenko <zxteam@pm.me>", "kyren <catherine@chucklefish.org>"]
 edition = "2021"
 repository = "https://github.com/khvzak/mlua"
@@ -9,8 +9,6 @@ readme = "README.md"
 keywords = ["lua", "luajit", "luau", "async", "scripting"]
 categories = ["api-bindings", "asynchronous"]
 license = "MIT"
-links = "lua"
-build = "build/main.rs"
 description = """
 High level bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox Luau
 with async/await features and support of writing native Lua modules in Rust.
@@ -23,48 +21,43 @@ rustdoc-args = ["--cfg", "docsrs"]
 [workspace]
 members = [
     "mlua_derive",
+    "mlua-sys",
 ]
 
 [features]
-lua54 = []
-lua53 = []
-lua52 = []
-lua51 = []
-luajit = []
-luajit52 = ["luajit"]
-luau = ["luau0-src"]
-vendored = ["lua-src", "luajit-src"]
-module = ["mlua_derive"]
-async = ["futures-core", "futures-task", "futures-util"]
+lua54 = ["ffi/lua54"]
+lua53 = ["ffi/lua53"]
+lua52 = ["ffi/lua52"]
+lua51 = ["ffi/lua51"]
+luajit = ["ffi/luajit"]
+luajit52 = ["luajit", "ffi/luajit52"]
+luau = ["ffi/luau"]
+luau-jit = ["luau", "ffi/luau-codegen"]
+vendored = ["ffi/vendored"]
+module = ["mlua_derive", "ffi/module"]
+async = ["futures-util"]
 send = []
 serialize = ["serde", "erased-serde", "serde-value"]
 macros = ["mlua_derive/macros"]
 unstable = []
 
 [dependencies]
-mlua_derive = { version = "=0.9.0-beta.1", optional = true, path = "mlua_derive" }
+mlua_derive = { version = "=0.9.0-beta.2", optional = true, path = "mlua_derive" }
 bstr = { version = "1.0", features = ["std"], default_features = false }
 once_cell = { version = "1.0" }
 num-traits = { version = "0.2.14" }
 rustc-hash = "1.0"
-futures-core = { version = "0.3.5", optional = true }
-futures-task = { version = "0.3.5", optional = true }
-futures-util = { version = "0.3.5", optional = true }
+futures-util = { version = "0.3", optional = true, default-features = false, features = ["std"] }
 serde = { version = "1.0", optional = true }
 erased-serde = { version = "0.3", optional = true }
 serde-value = { version = "0.7", optional = true }
 parking_lot = { version = "0.12", optional = true }
 
-[build-dependencies]
-cc = { version = "1.0" }
-pkg-config = { version = "0.3.17" }
-lua-src = { version = ">= 544.0.0, < 550.0.0", optional = true }
-luajit-src = { version = ">= 210.4.0, < 220.0.0", optional = true }
-luau0-src = { version = "0.5.0", optional = true }
+ffi = { package = "mlua-sys", version = "0.2.0", path = "mlua-sys" }
 
 [dev-dependencies]
 rustyline = "11.0"
-criterion = { version = "0.4", features = ["html_reports", "async_tokio"] }
+criterion = { version = "0.5", features = ["async_tokio"] }
 trybuild = "1.0"
 futures = "0.3.5"
 hyper = { version = "0.14", features = ["client", "server"] }

README.md

@@ -45,6 +45,7 @@ Below is a list of the available feature flags. By default `mlua` does not enabl
 * `luajit`: activate [LuaJIT] support
 * `luajit52`: activate [LuaJIT] support with partial compatibility with Lua 5.2
 * `luau`: activate [Luau] support (auto vendored mode)
+* `luau-jit`: activate [Luau] support with experimental jit backend. This is unstable feature and not recommended to use.
 * `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])

build/find_dummy.rs

@@ -1,5 +0,0 @@
-use std::path::PathBuf;
-
-pub fn probe_lua() -> Option<PathBuf> {
-    None
-}

build/main.rs

@@ -1,115 +0,0 @@
-#[cfg_attr(
-    any(
-        feature = "luau",
-        all(
-            feature = "vendored",
-            any(
-                feature = "lua54",
-                feature = "lua53",
-                feature = "lua52",
-                feature = "lua51",
-                feature = "luajit"
-            )
-        )
-    ),
-    path = "find_vendored.rs"
-)]
-#[cfg_attr(
-    all(
-        not(feature = "vendored"),
-        any(
-            feature = "lua54",
-            feature = "lua53",
-            feature = "lua52",
-            feature = "lua51",
-            feature = "luajit"
-        )
-    ),
-    path = "find_normal.rs"
-)]
-#[cfg_attr(
-    not(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "lua51",
-        feature = "luajit",
-        feature = "luau"
-    )),
-    path = "find_dummy.rs"
-)]
-mod find;
-
-fn main() {
-    #[cfg(not(any(
-        feature = "lua54",
-        feature = "lua53",
-        feature = "lua52",
-        feature = "lua51",
-        feature = "luajit",
-        feature = "luau"
-    )))]
-    compile_error!(
-        "You must enable one of the features: lua54, lua53, lua52, lua51, luajit, luajit52, luau"
-    );
-
-    #[cfg(all(
-        feature = "lua54",
-        any(
-            feature = "lua53",
-            feature = "lua52",
-            feature = "lua51",
-            feature = "luajit",
-            feature = "luau"
-        )
-    ))]
-    compile_error!(
-        "You can enable only one of the features: lua54, lua53, lua52, lua51, luajit, luajit52, luau"
-    );
-
-    #[cfg(all(
-        feature = "lua53",
-        any(
-            feature = "lua52",
-            feature = "lua51",
-            feature = "luajit",
-            feature = "luau"
-        )
-    ))]
-    compile_error!(
-        "You can enable only one of the features: lua54, lua53, lua52, lua51, luajit, luajit52, luau"
-    );
-
-    #[cfg(all(
-        feature = "lua52",
-        any(feature = "lua51", feature = "luajit", feature = "luau")
-    ))]
-    compile_error!(
-        "You can enable only one of the features: lua54, lua53, lua52, lua51, luajit, luajit52, luau"
-    );
-
-    #[cfg(all(feature = "lua51", any(feature = "luajit", feature = "luau")))]
-    compile_error!(
-        "You can enable only one of the features: lua54, lua53, lua52, lua51, luajit, luajit52, luau"
-    );
-
-    #[cfg(all(feature = "luajit", feature = "luau"))]
-    compile_error!(
-        "You can enable only one of the features: lua54, lua53, lua52, lua51, luajit, luajit52, luau"
-    );
-
-    // We don't support "vendored module" mode on windows
-    #[cfg(all(feature = "vendored", feature = "module", target_os = "windows"))]
-    compile_error!(
-        "Vendored (static) builds are not supported for modules on Windows.\n"
-            + "Please, use `pkg-config` or custom mode to link to a Lua dll."
-    );
-
-    #[cfg(all(feature = "luau", feature = "module"))]
-    compile_error!("Luau does not support module mode");
-
-    #[cfg(any(not(feature = "module"), target_os = "windows"))]
-    find::probe_lua();
-
-    println!("cargo:rerun-if-changed=build");
-}

mlua-sys/Cargo.toml

@@ -0,0 +1,41 @@
+[package]
+name = "mlua-sys"
+version = "0.2.0"
+authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
+edition = "2021"
+repository = "https://github.com/khvzak/mlua"
+documentation = "https://docs.rs/mlua-sys"
+readme = "README.md"
+categories = ["external-ffi-bindings"]
+license = "MIT"
+links = "lua"
+build = "build/main.rs"
+description = """
+Low level (FFI) bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox Luau
+"""
+
+[package.metadata.docs.rs]
+features = ["lua54", "vendored"]
+rustdoc-args = ["--cfg", "docsrs"]
+
+[features]
+lua54 = []
+lua53 = []
+lua52 = []
+lua51 = []
+luajit = []
+luajit52 = ["luajit"]
+luau = ["luau0-src"]
+luau-codegen = ["luau"]
+vendored = ["lua-src", "luajit-src"]
+module = []
+
+[dependencies]
+
+[build-dependencies]
+cc = "1.0"
+cfg-if = "1.0"
+pkg-config = "0.3.17"
+lua-src = { version = ">= 546.0.0, < 550.0.0", optional = true }
+luajit-src = { version = ">= 210.4.0, < 220.0.0", optional = true }
+luau0-src = { version = "0.5.8", optional = true }

mlua-sys/README.md

@@ -0,0 +1,8 @@
+# mlua-sys
+
+Low level (FFI) bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox [Luau].
+
+Intended to be consumed by the [mlua] crate.
+
+[Luau]: https://github.com/Roblox/luau
+[mlua]: https://crates.io/crates/mlua

mlua-sys/build/find_vendored.rs

@@ -5,22 +5,25 @@ use std::path::PathBuf;
 pub fn probe_lua() -> Option<PathBuf> {
     #[cfg(feature = "lua54")]
     let artifacts = lua_src::Build::new().build(lua_src::Lua54);
+
     #[cfg(feature = "lua53")]
     let artifacts = lua_src::Build::new().build(lua_src::Lua53);
+
     #[cfg(feature = "lua52")]
     let artifacts = lua_src::Build::new().build(lua_src::Lua52);
+
     #[cfg(feature = "lua51")]
     let artifacts = lua_src::Build::new().build(lua_src::Lua51);
+
     #[cfg(feature = "luajit")]
-    let artifacts = {
-        let mut builder = luajit_src::Build::new();
-        if cfg!(feature = "luajit52") {
-            builder.lua52compat(true);
-        }
-        builder.build()
-    };
+    let artifacts = luajit_src::Build::new()
+        .lua52compat(cfg!(feature = "luajit52"))
+        .build();
+
     #[cfg(feature = "luau")]
-    let artifacts = luau0_src::Build::new().build();
+    let artifacts = luau0_src::Build::new()
+        .enable_codegen(cfg!(feature = "luau-codegen"))
+        .build();
 
     artifacts.print_cargo_metadata();
 

mlua-sys/build/main.rs

@@ -0,0 +1,19 @@
+cfg_if::cfg_if! {
+    if #[cfg(all(feature = "lua54", not(any(feature = "lua53", feature = "lua52", feature = "lua51", feature = "luajit", feature = "luau"))))] {
+        include!("main_inner.rs");
+    } else if #[cfg(all(feature = "lua53", not(any(feature = "lua54", feature = "lua52", feature = "lua51", feature = "luajit", feature = "luau"))))] {
+        include!("main_inner.rs");
+    } else if #[cfg(all(feature = "lua52", not(any(feature = "lua54", feature = "lua53", feature = "lua51", feature = "luajit", feature = "luau"))))] {
+        include!("main_inner.rs");
+    } else if #[cfg(all(feature = "lua51", not(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "luajit", feature = "luau"))))] {
+        include!("main_inner.rs");
+    } else if #[cfg(all(feature = "luajit", not(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "lua51", feature = "luau"))))] {
+        include!("main_inner.rs");
+    } else if #[cfg(all(feature = "luau", not(any(feature = "lua54", feature = "lua53", feature = "lua52", feature = "lua51", feature = "luajit"))))] {
+        include!("main_inner.rs");
+    } else {
+        fn main() {
+            compile_error!("You can enable only one of the features: lua54, lua53, lua52, lua51, luajit, luajit52, luau");
+        }
+    }
+}

mlua-sys/build/main_inner.rs

@@ -0,0 +1,26 @@
+cfg_if::cfg_if! {
+    if #[cfg(any(feature = "luau", feature = "vendored"))] {
+        #[path = "find_vendored.rs"]
+        mod find;
+    } else {
+        #[path = "find_normal.rs"]
+        mod find;
+    }
+}
+
+fn main() {
+    // We don't support "vendored module" mode on windows
+    #[cfg(all(feature = "vendored", feature = "module", target_os = "windows"))]
+    compile_error!(
+        "Vendored (static) builds are not supported for modules on Windows.\n"
+            + "Please, use `pkg-config` or custom mode to link to a Lua dll."
+    );
+
+    #[cfg(all(feature = "luau", feature = "module"))]
+    compile_error!("Luau does not support module mode");
+
+    #[cfg(any(not(feature = "module"), target_os = "windows"))]
+    find::probe_lua();
+
+    println!("cargo:rerun-if-changed=build");
+}

mlua-sys/src/lib.rs

@@ -1,44 +1,52 @@
-//! Low level bindings to Lua 5.4/5.3/5.2/5.1 including LuaJIT.
+//! Low level bindings to Lua 5.4/5.3/5.2/5.1 (including LuaJIT) and Roblox Luau.
 
 #![allow(non_camel_case_types, non_snake_case, dead_code)]
+#![allow(clippy::missing_safety_doc)]
+#![doc(test(attr(deny(warnings))))]
+#![cfg_attr(docsrs, feature(doc_cfg))]
 
 use std::os::raw::c_int;
 
-#[cfg(feature = "lua54")]
+#[cfg(any(feature = "lua54", doc))]
 pub use lua54::*;
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua53", doc))]
 pub use lua53::*;
 
-#[cfg(feature = "lua52")]
+#[cfg(any(feature = "lua52", doc))]
 pub use lua52::*;
 
-#[cfg(any(feature = "lua51", feature = "luajit"))]
+#[cfg(any(feature = "lua51", feature = "luajit", doc))]
 pub use lua51::*;
 
-#[cfg(feature = "luau")]
+#[cfg(any(feature = "luau", doc))]
 pub use luau::*;
 
 #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+#[doc(hidden)]
 pub const LUA_MAX_UPVALUES: c_int = 255;
 
 #[cfg(any(feature = "lua51", all(feature = "luajit", not(feature = "vendored"))))]
+#[doc(hidden)]
 pub const LUA_MAX_UPVALUES: c_int = 60;
 
 #[cfg(all(feature = "luajit", feature = "vendored"))]
+#[doc(hidden)]
 pub const LUA_MAX_UPVALUES: c_int = 120;
 
 #[cfg(feature = "luau")]
+#[doc(hidden)]
 pub const LUA_MAX_UPVALUES: c_int = 200;
 
 // I believe `luaL_traceback` < 5.4 requires this much free stack to not error.
 // 5.4 uses `luaL_Buffer`
+#[doc(hidden)]
 pub const LUA_TRACEBACK_STACK: c_int = 11;
 
 // The minimum alignment guaranteed by the architecture. This value is used to
 // add fast paths for low alignment values.
 // Copied from https://github.com/rust-lang/rust/blob/master/library/std/src/sys/common/alloc.rs
-#[cfg(all(any(
+#[cfg(any(
     target_arch = "x86",
     target_arch = "arm",
     target_arch = "mips",
@@ -50,9 +58,10 @@ pub const LUA_TRACEBACK_STACK: c_int = 11;
     target_arch = "hexagon",
     all(target_arch = "riscv32", not(target_os = "espidf")),
     all(target_arch = "xtensa", not(target_os = "espidf")),
-)))]
+))]
+#[doc(hidden)]
 pub const SYS_MIN_ALIGN: usize = 8;
-#[cfg(all(any(
+#[cfg(any(
     target_arch = "x86_64",
     target_arch = "aarch64",
     target_arch = "mips64",
@@ -60,45 +69,36 @@ pub const SYS_MIN_ALIGN: usize = 8;
     target_arch = "sparc64",
     target_arch = "riscv64",
     target_arch = "wasm64",
-)))]
+))]
+#[doc(hidden)]
 pub const SYS_MIN_ALIGN: usize = 16;
 // The allocator on the esp-idf platform guarentees 4 byte alignment.
-#[cfg(all(any(
+#[cfg(any(
     all(target_arch = "riscv32", target_os = "espidf"),
     all(target_arch = "xtensa", target_os = "espidf"),
-)))]
+))]
+#[doc(hidden)]
 pub const SYS_MIN_ALIGN: usize = 4;
 
-// Hack to avoid stripping a few unused Lua symbols that could be imported
-// by C modules in unsafe mode
-#[cfg(not(feature = "luau"))]
-pub(crate) fn keep_lua_symbols() {
-    let mut _symbols: Vec<*const extern "C" fn()> = vec![
-        lua_atpanic as _,
-        lua_isuserdata as _,
-        lua_tocfunction as _,
-        luaL_loadstring as _,
-        luaL_openlibs as _,
-    ];
-    #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
-    {
-        _symbols.push(lua_getglobal as _);
-        _symbols.push(lua_setglobal as _);
-        _symbols.push(luaL_setfuncs as _);
-    }
-}
+#[macro_use]
+mod macros;
 
-#[cfg(feature = "lua54")]
+#[cfg(any(feature = "lua54", doc))]
+#[cfg_attr(docsrs, doc(cfg(feature = "lua54")))]
 pub mod lua54;
 
-#[cfg(feature = "lua53")]
+#[cfg(any(feature = "lua53", doc))]
+#[cfg_attr(docsrs, doc(cfg(feature = "lua53")))]
 pub mod lua53;
 
-#[cfg(feature = "lua52")]
+#[cfg(any(feature = "lua52", doc))]
+#[cfg_attr(docsrs, doc(cfg(feature = "lua52")))]
 pub mod lua52;
 
-#[cfg(any(feature = "lua51", feature = "luajit"))]
+#[cfg(any(feature = "lua51", feature = "luajit", doc))]
+#[cfg_attr(docsrs, doc(cfg(any(feature = "lua51", feature = "luajit"))))]
 pub mod lua51;
 
-#[cfg(feature = "luau")]
+#[cfg(any(feature = "luau", doc))]
+#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
 pub mod luau;

mlua-sys/src/lua51/compat.rs

@@ -486,10 +486,10 @@ pub unsafe fn luaL_traceback(
     lua_concat(L, lua_gettop(L) - top);
 }
 
-pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char {
+pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize) -> *const c_char {
+    idx = lua_absindex(L, idx);
     if luaL_callmeta(L, idx, cstr!("__tostring")) == 0 {
-        let t = lua_type(L, idx);
-        match t {
+        match lua_type(L, idx) {
             LUA_TNIL => {
                 lua_pushliteral(L, "nil");
             }
@@ -503,7 +503,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
                     lua_pushliteral(L, "true");
                 }
             }
-            _ => {
+            t => {
                 let tt = luaL_getmetafield(L, idx, cstr!("__name"));
                 let name = if tt == LUA_TSTRING {
                     lua_tostring(L, -1)
@@ -512,7 +512,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
                 };
                 lua_pushfstring(L, cstr!("%s: %p"), name, lua_topointer(L, idx));
                 if tt != LUA_TNIL {
-                    lua_replace(L, -2);
+                    lua_replace(L, -2); // remove '__name'
                 }
             }
         };

mlua-sys/src/lua52/compat.rs

@@ -205,10 +205,10 @@ pub unsafe fn luaL_newmetatable(L: *mut lua_State, tname: *const c_char) -> c_in
     }
 }
 
-pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char {
+pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize) -> *const c_char {
+    idx = lua_absindex(L, idx);
     if luaL_callmeta(L, idx, cstr!("__tostring")) == 0 {
-        let t = lua_type(L, idx);
-        match t {
+        match lua_type(L, idx) {
             LUA_TNIL => {
                 lua_pushliteral(L, "nil");
             }
@@ -222,7 +222,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
                     lua_pushliteral(L, "true");
                 }
             }
-            _ => {
+            t => {
                 let tt = luaL_getmetafield(L, idx, cstr!("__name"));
                 let name = if tt == LUA_TSTRING {
                     lua_tostring(L, -1)
@@ -231,7 +231,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
                 };
                 lua_pushfstring(L, cstr!("%s: %p"), name, lua_topointer(L, idx));
                 if tt != LUA_TNIL {
-                    lua_replace(L, -2);
+                    lua_replace(L, -2); // remove '__name'
                 }
             }
         };

mlua-sys/src/lua53/compat.rs

@@ -1,4 +1,4 @@
-//! MLua compatibility layer for Lua 5.2
+//! MLua compatibility layer for Lua 5.3
 
 use std::os::raw::c_int;
 

mlua-sys/src/lua53/lauxlib.rs

@@ -25,7 +25,8 @@ extern "C" {
 
     pub fn luaL_getmetafield(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
     pub fn luaL_callmeta(L: *mut lua_State, obj: c_int, e: *const c_char) -> c_int;
-    pub fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char;
+    #[link_name = "luaL_tolstring"]
+    pub fn luaL_tolstring_(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char;
     pub fn luaL_argerror(L: *mut lua_State, arg: c_int, extramsg: *const c_char) -> c_int;
     pub fn luaL_checklstring(L: *mut lua_State, arg: c_int, l: *mut usize) -> *const c_char;
     pub fn luaL_optlstring(
@@ -167,6 +168,11 @@ pub unsafe fn luaL_getmetatable(L: *mut lua_State, n: *const c_char) {
     lua::lua_getfield(L, lua::LUA_REGISTRYINDEX, n);
 }
 
+#[inline(always)]
+pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char {
+    luaL_tolstring_(L, lua::lua_absindex(L, idx), len)
+}
+
 // luaL_opt would be implemented here but it is undocumented, so it's omitted
 
 #[inline(always)]

mlua-sys/src/lua54/lua.rs

@@ -112,7 +112,10 @@ extern "C" {
     pub fn lua_newstate(f: lua_Alloc, ud: *mut c_void) -> *mut lua_State;
     pub fn lua_close(L: *mut lua_State);
     pub fn lua_newthread(L: *mut lua_State) -> *mut lua_State;
+    // Deprecated in Lua 5.4.6
     pub fn lua_resetthread(L: *mut lua_State) -> c_int;
+    #[cfg(feature = "vendored")]
+    pub fn lua_closethread(L: *mut lua_State, from: *mut lua_State) -> c_int;
 
     pub fn lua_atpanic(L: *mut lua_State, panicf: lua_CFunction) -> lua_CFunction;
 

mlua-sys/src/luau/compat.rs

@@ -436,10 +436,10 @@ pub unsafe fn luaL_traceback(
     lua_concat(L, lua_gettop(L) - top);
 }
 
-pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) -> *const c_char {
+pub unsafe fn luaL_tolstring(L: *mut lua_State, mut idx: c_int, len: *mut usize) -> *const c_char {
+    idx = lua_absindex(L, idx);
     if luaL_callmeta(L, idx, cstr!("__tostring")) == 0 {
-        let t = lua_type(L, idx);
-        match t {
+        match lua_type(L, idx) {
             LUA_TNIL => {
                 lua_pushliteral(L, "nil");
             }
@@ -453,7 +453,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
                     lua_pushliteral(L, "true");
                 }
             }
-            _ => {
+            t => {
                 let tt = luaL_getmetafield(L, idx, cstr!("__name"));
                 let name = if tt == LUA_TSTRING {
                     lua_tostring(L, -1)
@@ -462,7 +462,7 @@ pub unsafe fn luaL_tolstring(L: *mut lua_State, idx: c_int, len: *mut usize) ->
                 };
                 lua_pushfstring(L, cstr!("%s: %p"), name, lua_topointer(L, idx));
                 if tt != LUA_TNIL {
-                    lua_replace(L, -2);
+                    lua_replace(L, -2); // remove '__name'
                 }
             }
         };

mlua-sys/src/luau/lua.rs

@@ -74,6 +74,7 @@ pub type lua_Continuation = unsafe extern "C" fn(L: *mut lua_State, status: c_in
 
 /// Type for userdata destructor functions.
 pub type lua_Udestructor = unsafe extern "C" fn(*mut c_void);
+pub type lua_Destructor = unsafe extern "C" fn(L: *mut lua_State, *mut c_void);
 
 /// Type for memory-allocation functions.
 pub type lua_Alloc = unsafe extern "C" fn(
@@ -83,6 +84,11 @@ pub type lua_Alloc = unsafe extern "C" fn(
     nsize: usize,
 ) -> *mut c_void;
 
+/// Returns Luau release version (eg. `0.xxx`).
+pub const fn luau_version() -> Option<&'static str> {
+    option_env!("LUAU_VERSION")
+}
+
 extern "C" {
     //
     // State manipulation
@@ -265,11 +271,8 @@ extern "C" {
     // TODO: lua_encodepointer
     pub fn lua_clock() -> c_double;
     pub fn lua_setuserdatatag(L: *mut lua_State, idx: c_int, tag: c_int);
-    pub fn lua_setuserdatadtor(
-        L: *mut lua_State,
-        tag: c_int,
-        dtor: Option<unsafe extern "C" fn(*mut lua_State, *mut c_void)>,
-    );
+    pub fn lua_setuserdatadtor(L: *mut lua_State, tag: c_int, dtor: Option<lua_Destructor>);
+    pub fn lua_getuserdatadtor(L: *mut lua_State, tag: c_int) -> Option<lua_Destructor>;
     pub fn lua_clonefunction(L: *mut lua_State, idx: c_int);
     pub fn lua_cleartable(L: *mut lua_State, idx: c_int);
 }

mlua-sys/src/luau/luacodegen.rs

@@ -0,0 +1,11 @@
+//! Contains definitions from `luacodegen.h`.
+
+use std::os::raw::c_int;
+
+use super::lua::lua_State;
+
+extern "C" {
+    pub fn luau_codegen_supported() -> c_int;
+    pub fn luau_codegen_create(state: *mut lua_State);
+    pub fn luau_codegen_compile(state: *mut lua_State, idx: c_int);
+}

mlua-sys/src/luau/mod.rs

@@ -4,10 +4,12 @@ pub use compat::*;
 pub use lauxlib::*;
 pub use lua::*;
 pub use luacode::*;
+pub use luacodegen::*;
 pub use lualib::*;
 
 pub mod compat;
 pub mod lauxlib;
 pub mod lua;
 pub mod luacode;
+pub mod luacodegen;
 pub mod lualib;

mlua-sys/src/macros.rs

@@ -0,0 +1,7 @@
+#[allow(unused_macros)]
+macro_rules! cstr {
+    ($s:expr) => {
+        concat!($s, "\0") as *const str as *const [::std::os::raw::c_char]
+            as *const ::std::os::raw::c_char
+    };
+}

mlua_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua_derive"
-version = "0.9.0-beta.1"
+version = "0.9.0-beta.2"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 edition = "2021"
 description = "Procedural macros for the mlua crate."

mlua_derive/src/lib.rs

@@ -42,7 +42,7 @@ pub fn lua_module(attr: TokenStream, item: TokenStream) -> TokenStream {
     }
 
     let func = parse_macro_input!(item as ItemFn);
-    let func_name = func.sig.ident.clone();
+    let func_name = &func.sig.ident;
     let module_name = args.name.unwrap_or_else(|| func_name.clone());
     let ext_entrypoint_name = Ident::new(&format!("luaopen_{module_name}"), Span::call_site());
 
@@ -84,26 +84,26 @@ pub fn chunk(input: TokenStream) -> TokenStream {
     });
 
     let wrapped_code = quote! {{
-        use ::mlua::{AsChunk, ChunkMode, Lua, Result, Value};
+        use ::mlua::{AsChunk, ChunkMode, Lua, Result, Table};
         use ::std::borrow::Cow;
         use ::std::io::Result as IoResult;
         use ::std::sync::Mutex;
 
-        struct InnerChunk<F: for <'a> FnOnce(&'a Lua) -> Result<Value<'a>>>(Mutex<Option<F>>);
+        struct InnerChunk<F: for <'a> FnOnce(&'a Lua) -> Result<Table<'a>>>(Mutex<Option<F>>);
 
         impl<F> AsChunk<'static> for InnerChunk<F>
         where
-            F: for <'a> FnOnce(&'a Lua) -> Result<Value<'a>>,
+            F: for <'a> FnOnce(&'a Lua) -> Result<Table<'a>>,
         {
-            fn env<'lua>(&self, lua: &'lua Lua) -> Result<Value<'lua>> {
+            fn environment<'lua>(&self, lua: &'lua Lua) -> Result<Option<Table<'lua>>> {
                 if #caps_len > 0 {
                     if let Ok(mut make_env) = self.0.lock() {
                         if let Some(make_env) = make_env.take() {
-                            return make_env(lua);
+                            return make_env(lua).map(Some);
                         }
                     }
                 }
-                Ok(Value::Nil)
+                Ok(None)
             }
 
             fn mode(&self) -> Option<ChunkMode> {
@@ -115,9 +115,9 @@ pub fn chunk(input: TokenStream) -> TokenStream {
             }
         }
 
-        fn annotate<F: for<'a> FnOnce(&'a Lua) -> Result<Value<'a>>>(f: F) -> F { f }
+        fn annotate<F: for<'a> FnOnce(&'a Lua) -> Result<Table<'a>>>(f: F) -> F { f }
 
-        let make_env = annotate(move |lua: &Lua| -> Result<Value> {
+        let make_env = annotate(move |lua: &Lua| -> Result<Table> {
             let globals = lua.globals();
             let env = lua.create_table()?;
             let meta = lua.create_table()?;
@@ -128,7 +128,7 @@ pub fn chunk(input: TokenStream) -> TokenStream {
             #(#caps)*
 
             env.set_metatable(Some(meta));
-            Ok(Value::Table(env))
+            Ok(env)
         });
 
         InnerChunk(Mutex::new(Some(make_env)))

src/chunk.rs

@@ -5,14 +5,14 @@ use std::io::Result as IoResult;
 use std::path::{Path, PathBuf};
 use std::string::String as StdString;
 
-use crate::error::{Error, Result};
-use crate::ffi;
+use crate::error::{Error, ErrorContext, Result};
 use crate::function::Function;
 use crate::lua::Lua;
-use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti, Value};
+use crate::table::Table;
+use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti};
 
 #[cfg(feature = "async")]
-use {futures_core::future::LocalBoxFuture, futures_util::future};
+use futures_util::future::{self, LocalBoxFuture};
 
 /// Trait for types [loadable by Lua] and convertible to a [`Chunk`]
 ///
@@ -27,9 +27,9 @@ pub trait AsChunk<'a> {
     /// Returns optional chunk [environment]
     ///
     /// [environment]: https://www.lua.org/manual/5.4/manual.html#2.2
-    fn env<'lua>(&self, lua: &'lua Lua) -> Result<Value<'lua>> {
+    fn environment<'lua>(&self, lua: &'lua Lua) -> Result<Option<Table<'lua>>> {
         let _lua = lua; // suppress warning
-        Ok(Value::Nil)
+        Ok(None)
     }
 
     /// Returns optional chunk mode (text or binary)
@@ -104,7 +104,7 @@ impl AsChunk<'static> for PathBuf {
 pub struct Chunk<'lua, 'a> {
     pub(crate) lua: &'lua Lua,
     pub(crate) name: StdString,
-    pub(crate) env: Result<Value<'lua>>,
+    pub(crate) env: Result<Option<Table<'lua>>>,
     pub(crate) mode: Option<ChunkMode>,
     pub(crate) source: IoResult<Cow<'a, [u8]>>,
     #[cfg(feature = "luau")]
@@ -255,9 +255,9 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
         self
     }
 
-    /// Sets the first upvalue (`_ENV`) of the loaded chunk to the given value.
+    /// Sets the environment of the loaded chunk to the given value.
     ///
-    /// Lua main chunks always have exactly one upvalue, and this upvalue is used as the `_ENV`
+    /// In Lua >=5.2 main chunks always have exactly one upvalue, and this upvalue is used as the `_ENV`
     /// variable inside the chunk. By default this value is set to the global environment.
     ///
     /// Calling this method changes the `_ENV` upvalue to the value provided, and variables inside
@@ -267,7 +267,10 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     /// necessary to populate the environment in order for scripts using custom environments to be
     /// useful.
     pub fn set_environment<V: IntoLua<'lua>>(mut self, env: V) -> Self {
-        self.env = env.into_lua(self.lua);
+        self.env = env
+            .into_lua(self.lua)
+            .and_then(|val| self.lua.unpack(val))
+            .context("bad environment value");
         self
     }
 
@@ -415,7 +418,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
                     self.mode = Some(ChunkMode::Binary);
                 }
                 #[cfg(not(feature = "luau"))]
-                if let Ok(func) = self.lua.load_chunk(None, Value::Nil, None, source.as_ref()) {
+                if let Ok(func) = self.lua.load_chunk(None, None, None, source.as_ref()) {
                     let data = func.dump(false);
                     self.source = Ok(Cow::Owned(data));
                     self.mode = Some(ChunkMode::Binary);
@@ -455,7 +458,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
                     } else {
                         let mut cache = ChunksCache(HashMap::new());
                         cache.0.insert(text_source, binary_source.as_ref().to_vec());
-                        self.lua.set_app_data(cache);
+                        let _ = self.lua.try_set_app_data(cache);
                     }
                 }
             }

src/conversion.rs

@@ -9,7 +9,7 @@ use bstr::{BStr, BString};
 use num_traits::cast;
 
 use crate::error::{Error, Result};
-use crate::function::Function;
+use crate::function::{Function, WrappedFunction};
 use crate::lua::Lua;
 use crate::string::String;
 use crate::table::Table;
@@ -18,14 +18,10 @@ use crate::types::{LightUserData, MaybeSend};
 use crate::userdata::{AnyUserData, UserData, UserDataRef, UserDataRefMut};
 use crate::value::{FromLua, IntoLua, Nil, Value};
 
-#[cfg(feature = "unstable")]
-use crate::{
-    function::{OwnedFunction, WrappedFunction},
-    table::OwnedTable,
-    userdata::OwnedAnyUserData,
-};
+#[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+use crate::{function::OwnedFunction, table::OwnedTable, userdata::OwnedAnyUserData};
 
-#[cfg(all(feature = "async", feature = "unstable"))]
+#[cfg(feature = "async")]
 use crate::function::WrappedAsyncFunction;
 
 impl<'lua> IntoLua<'lua> for Value<'lua> {
@@ -83,7 +79,8 @@ impl<'lua> FromLua<'lua> for Table<'lua> {
     }
 }
 
-#[cfg(feature = "unstable")]
+#[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
 impl<'lua> IntoLua<'lua> for OwnedTable {
     #[inline]
     fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
@@ -91,7 +88,8 @@ impl<'lua> IntoLua<'lua> for OwnedTable {
     }
 }
 
-#[cfg(feature = "unstable")]
+#[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
 impl<'lua> FromLua<'lua> for OwnedTable {
     #[inline]
     fn from_lua(value: Value<'lua>, lua: &'lua Lua) -> Result<OwnedTable> {
@@ -120,7 +118,8 @@ impl<'lua> FromLua<'lua> for Function<'lua> {
     }
 }
 
-#[cfg(feature = "unstable")]
+#[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
 impl<'lua> IntoLua<'lua> for OwnedFunction {
     #[inline]
     fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
@@ -128,7 +127,8 @@ impl<'lua> IntoLua<'lua> for OwnedFunction {
     }
 }
 
-#[cfg(feature = "unstable")]
+#[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
 impl<'lua> FromLua<'lua> for OwnedFunction {
     #[inline]
     fn from_lua(value: Value<'lua>, lua: &'lua Lua) -> Result<OwnedFunction> {
@@ -136,7 +136,6 @@ impl<'lua> FromLua<'lua> for OwnedFunction {
     }
 }
 
-#[cfg(feature = "unstable")]
 impl<'lua> IntoLua<'lua> for WrappedFunction<'lua> {
     #[inline]
     fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
@@ -144,7 +143,7 @@ impl<'lua> IntoLua<'lua> for WrappedFunction<'lua> {
     }
 }
 
-#[cfg(all(feature = "async", feature = "unstable"))]
+#[cfg(feature = "async")]
 impl<'lua> IntoLua<'lua> for WrappedAsyncFunction<'lua> {
     #[inline]
     fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
@@ -194,7 +193,8 @@ impl<'lua> FromLua<'lua> for AnyUserData<'lua> {
     }
 }
 
-#[cfg(feature = "unstable")]
+#[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
 impl<'lua> IntoLua<'lua> for OwnedAnyUserData {
     #[inline]
     fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
@@ -202,7 +202,8 @@ impl<'lua> IntoLua<'lua> for OwnedAnyUserData {
     }
 }
 
-#[cfg(feature = "unstable")]
+#[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+#[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
 impl<'lua> FromLua<'lua> for OwnedAnyUserData {
     #[inline]
     fn from_lua(value: Value<'lua>, lua: &'lua Lua) -> Result<OwnedAnyUserData> {

src/error.rs

@@ -335,6 +335,10 @@ impl StdError for Error {
             // Given that we include source to fmt::Display implementation for `CallbackError`, this call returns nothing.
             Error::CallbackError { .. } => None,
             Error::ExternalError(ref err) => err.source(),
+            Error::WithContext { ref cause, .. } => match cause.as_ref() {
+                Error::ExternalError(err) => err.source(),
+                _ => None,
+            },
             _ => None,
         }
     }
@@ -353,6 +357,10 @@ impl Error {
     {
         match self {
             Error::ExternalError(err) => err.downcast_ref(),
+            Error::WithContext { cause, .. } => match cause.as_ref() {
+                Error::ExternalError(err) => err.downcast_ref(),
+                _ => None,
+            },
             _ => None,
         }
     }
@@ -414,33 +422,35 @@ pub trait ErrorContext: Sealed {
 
 impl ErrorContext for Error {
     fn context<C: fmt::Display>(self, context: C) -> Self {
-        Error::WithContext {
-            context: context.to_string(),
-            cause: Arc::new(self),
+        let context = context.to_string();
+        match self {
+            Error::WithContext { cause, .. } => Error::WithContext { context, cause },
+            _ => Error::WithContext {
+                context,
+                cause: Arc::new(self),
+            },
         }
     }
 
     fn with_context<C: fmt::Display>(self, f: impl FnOnce(&Error) -> C) -> Self {
-        Error::WithContext {
-            context: f(&self).to_string(),
-            cause: Arc::new(self),
+        let context = f(&self).to_string();
+        match self {
+            Error::WithContext { cause, .. } => Error::WithContext { context, cause },
+            _ => Error::WithContext {
+                context,
+                cause: Arc::new(self),
+            },
         }
     }
 }
 
 impl<T> ErrorContext for StdResult<T, Error> {
     fn context<C: fmt::Display>(self, context: C) -> Self {
-        self.map_err(|err| Error::WithContext {
-            context: context.to_string(),
-            cause: Arc::new(err),
-        })
+        self.map_err(|err| err.context(context))
     }
 
     fn with_context<C: fmt::Display>(self, f: impl FnOnce(&Error) -> C) -> Self {
-        self.map_err(|err| Error::WithContext {
-            context: f(&err).to_string(),
-            cause: Arc::new(err),
-        })
+        self.map_err(|err| err.with_context(f))
     }
 }
 

src/function.rs

@@ -1,36 +1,36 @@
+use std::cell::RefCell;
 use std::mem;
 use std::os::raw::{c_int, c_void};
 use std::ptr;
 use std::slice;
 
 use crate::error::{Error, Result};
-use crate::ffi;
+use crate::lua::Lua;
 use crate::memory::MemoryState;
-use crate::types::LuaRef;
+use crate::table::Table;
+use crate::types::{Callback, LuaRef, MaybeSend};
 use crate::util::{
     assert_stack, check_stack, error_traceback, pop_error, ptr_to_cstr_bytes, StackGuard,
 };
-use crate::value::{FromLuaMulti, IntoLuaMulti};
-
-#[cfg(feature = "unstable")]
-use {
-    crate::lua::Lua,
-    crate::types::{Callback, MaybeSend},
-    crate::value::IntoLua,
-    std::cell::RefCell,
-};
+use crate::value::{FromLuaMulti, IntoLua, IntoLuaMulti};
 
 #[cfg(feature = "async")]
-use {futures_core::future::LocalBoxFuture, futures_util::future};
-
-#[cfg(all(feature = "async", feature = "unstable"))]
-use {crate::types::AsyncCallback, futures_core::Future, futures_util::TryFutureExt};
+use {
+    crate::types::AsyncCallback,
+    futures_util::future::{self, Future, LocalBoxFuture, TryFutureExt},
+};
 
 /// Handle to an internal Lua function.
 #[derive(Clone, Debug)]
 pub struct Function<'lua>(pub(crate) LuaRef<'lua>);
 
 /// Owned handle to an internal Lua function.
+///
+/// The owned handle holds a *strong* reference to the current Lua instance.
+/// Be warned, if you place it into a Lua type (eg. [`UserData`] or a Rust callback), it is *very easy*
+/// to accidentally cause reference cycles that would prevent destroying Lua instance.
+///
+/// [`UserData`]: crate::UserData
 #[cfg(feature = "unstable")]
 #[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
 #[derive(Clone, Debug)]
@@ -39,20 +39,36 @@ pub struct OwnedFunction(pub(crate) crate::types::LuaOwnedRef);
 #[cfg(feature = "unstable")]
 impl OwnedFunction {
     /// Get borrowed handle to the underlying Lua function.
+    #[cfg_attr(feature = "send", allow(unused))]
     pub const fn to_ref(&self) -> Function {
         Function(self.0.to_ref())
     }
 }
 
+/// Contains information about a function.
+///
+/// Please refer to the [`Lua Debug Interface`] for more information.
+///
+/// [`Lua Debug Interface`]: https://www.lua.org/manual/5.4/manual.html#4.7
 #[derive(Clone, Debug)]
 pub struct FunctionInfo {
-    pub name: Option<Vec<u8>>,
-    pub name_what: Option<Vec<u8>>,
-    pub what: Option<Vec<u8>>,
+    /// A (reasonable) name of the function.
+    pub name: Option<String>,
+    /// Explains the `name` field ("global", "local", "method", "field", "upvalue", or "").
+    ///
+    /// Always `None` for Luau.
+    pub name_what: Option<String>,
+    /// A string "Lua" if the function is a Lua function, "C" if it is a C function, "main" if it is the main part of a chunk.
+    pub what: Option<String>,
+    /// The source of the chunk that created the function.
     pub source: Option<Vec<u8>>,
+    /// A "printable" version of source, to be used in error messages.
     pub short_src: Option<Vec<u8>>,
+    /// The line number where the definition of the function starts.
     pub line_defined: i32,
-    #[cfg(not(feature = "luau"))]
+    /// The line number where the definition of the function ends.
+    ///
+    /// Always `-1` for Luau.
     pub last_line_defined: i32,
 }
 
@@ -270,10 +286,113 @@ impl<'lua> Function<'lua> {
             "#,
         )
         .try_cache()
-        .set_name("_mlua_bind")
+        .set_name("__mlua_bind")
         .call((self.clone(), args_wrapper))
     }
 
+    /// Returns the environment of the Lua function.
+    ///
+    /// By default Lua functions shares a global environment.
+    ///
+    /// This function always returns `None` for Rust/C functions.
+    pub fn environment(&self) -> Option<Table> {
+        let lua = self.0.lua;
+        let state = lua.state();
+        unsafe {
+            let _sg = StackGuard::new(state);
+            assert_stack(state, 1);
+
+            lua.push_ref(&self.0);
+
+            let mut ar: ffi::lua_Debug = mem::zeroed();
+            #[cfg(not(feature = "luau"))]
+            {
+                ffi::lua_pushvalue(state, -1);
+                ffi::lua_getinfo(state, cstr!(">S"), &mut ar);
+            }
+            #[cfg(feature = "luau")]
+            ffi::lua_getinfo(state, -1, cstr!("s"), &mut ar);
+
+            if ptr_to_cstr_bytes(ar.what) == Some(b"C") {
+                return None;
+            }
+
+            #[cfg(any(feature = "lua51", feature = "luajit", feature = "luau"))]
+            ffi::lua_getfenv(state, -1);
+            #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+            for i in 1..=255 {
+                // Traverse upvalues until we find the _ENV one
+                match ffi::lua_getupvalue(state, -1, i) {
+                    s if s.is_null() => break,
+                    s if std::ffi::CStr::from_ptr(s as _).to_bytes() == b"_ENV" => break,
+                    _ => ffi::lua_pop(state, 1),
+                }
+            }
+
+            if ffi::lua_type(state, -1) != ffi::LUA_TTABLE {
+                return None;
+            }
+            Some(Table(lua.pop_ref()))
+        }
+    }
+
+    /// Sets the environment of the Lua function.
+    ///
+    /// The environment is a table that is used as the global environment for the function.
+    /// Returns `true` if environment successfully changed, `false` otherwise.
+    ///
+    /// This function does nothing for Rust/C functions.
+    pub fn set_environment(&self, env: Table) -> Result<bool> {
+        let lua = self.0.lua;
+        let state = lua.state();
+        unsafe {
+            let _sg = StackGuard::new(state);
+            check_stack(state, 2)?;
+
+            lua.push_ref(&self.0);
+
+            let mut ar: ffi::lua_Debug = mem::zeroed();
+            #[cfg(not(feature = "luau"))]
+            {
+                ffi::lua_pushvalue(state, -1);
+                ffi::lua_getinfo(state, cstr!(">S"), &mut ar);
+            }
+            #[cfg(feature = "luau")]
+            ffi::lua_getinfo(state, -1, cstr!("s"), &mut ar);
+
+            if ptr_to_cstr_bytes(ar.what) == Some(b"C") {
+                return Ok(false);
+            }
+
+            #[cfg(any(feature = "lua51", feature = "luajit", feature = "luau"))]
+            {
+                lua.push_ref(&env.0);
+                ffi::lua_setfenv(state, -2);
+            }
+            #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
+            for i in 1..=255 {
+                match ffi::lua_getupvalue(state, -1, i) {
+                    s if s.is_null() => return Ok(false),
+                    s if std::ffi::CStr::from_ptr(s as _).to_bytes() == b"_ENV" => {
+                        ffi::lua_pop(state, 1);
+                        // Create an anonymous function with the new environment
+                        let f_with_env = lua
+                            .load("return _ENV")
+                            .set_environment(env)
+                            .try_cache()
+                            .into_function()?;
+                        lua.push_ref(&f_with_env.0);
+                        ffi::lua_upvaluejoin(state, -2, i, -1, 1);
+                        break;
+                    }
+                    _ => ffi::lua_pop(state, 1),
+                }
+            }
+
+            Ok(true)
+        }
+    }
+
     /// Returns information about the function.
     ///
     /// Corresponds to the `>Sn` what mask for [`lua_getinfo`] when applied to the function.
@@ -295,12 +414,13 @@ impl<'lua> Function<'lua> {
             mlua_assert!(res != 0, "lua_getinfo failed with `>Sn`");
 
             FunctionInfo {
-                name: ptr_to_cstr_bytes(ar.name).map(|s| s.to_vec()),
+                name: ptr_to_cstr_bytes(ar.name).map(|s| String::from_utf8_lossy(s).into_owned()),
                 #[cfg(not(feature = "luau"))]
-                name_what: ptr_to_cstr_bytes(ar.namewhat).map(|s| s.to_vec()),
+                name_what: ptr_to_cstr_bytes(ar.namewhat)
+                    .map(|s| String::from_utf8_lossy(s).into_owned()),
                 #[cfg(feature = "luau")]
                 name_what: None,
-                what: ptr_to_cstr_bytes(ar.what).map(|s| s.to_vec()),
+                what: ptr_to_cstr_bytes(ar.what).map(|s| String::from_utf8_lossy(s).into_owned()),
                 source: ptr_to_cstr_bytes(ar.source).map(|s| s.to_vec()),
                 #[cfg(not(feature = "luau"))]
                 short_src: ptr_to_cstr_bytes(ar.short_src.as_ptr()).map(|s| s.to_vec()),
@@ -309,6 +429,8 @@ impl<'lua> Function<'lua> {
                 line_defined: ar.linedefined,
                 #[cfg(not(feature = "luau"))]
                 last_line_defined: ar.lastlinedefined,
+                #[cfg(feature = "luau")]
+                last_line_defined: -1,
             }
         }
     }
@@ -406,8 +528,8 @@ impl<'lua> Function<'lua> {
     }
 
     /// Convert this handle to owned version.
-    #[cfg(feature = "unstable")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
+    #[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
     #[inline]
     pub fn into_owned(self) -> OwnedFunction {
         OwnedFunction(self.0.into_owned())
@@ -420,22 +542,50 @@ impl<'lua> PartialEq for Function<'lua> {
     }
 }
 
+// Additional shortcuts
 #[cfg(feature = "unstable")]
+impl OwnedFunction {
+    /// Calls the function, passing `args` as function arguments.
+    ///
+    /// This is a shortcut for [`Function::call()`].
+    #[inline]
+    pub fn call<'lua, A, R>(&'lua self, args: A) -> Result<R>
+    where
+        A: IntoLuaMulti<'lua>,
+        R: FromLuaMulti<'lua>,
+    {
+        self.to_ref().call(args)
+    }
+
+    /// Returns a future that, when polled, calls `self`, passing `args` as function arguments,
+    /// and drives the execution.
+    ///
+    /// This is a shortcut for [`Function::call_async()`].
+    #[cfg(feature = "async")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+    #[inline]
+    pub fn call_async<'lua, A, R>(&'lua self, args: A) -> LocalBoxFuture<'lua, Result<R>>
+    where
+        A: IntoLuaMulti<'lua>,
+        R: FromLuaMulti<'lua> + 'lua,
+    {
+        self.to_ref().call_async(args)
+    }
+}
+
 pub(crate) struct WrappedFunction<'lua>(pub(crate) Callback<'lua, 'static>);
 
-#[cfg(all(feature = "async", feature = "unstable"))]
+#[cfg(feature = "async")]
 pub(crate) struct WrappedAsyncFunction<'lua>(pub(crate) AsyncCallback<'lua, 'static>);
 
-#[cfg(feature = "unstable")]
-#[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
 impl<'lua> Function<'lua> {
     /// Wraps a Rust function or closure, returning an opaque type that implements [`IntoLua`] trait.
     #[inline]
-    pub fn wrap<F, A, R>(func: F) -> impl IntoLua<'lua>
+    pub fn wrap<A, R, F>(func: F) -> impl IntoLua<'lua>
     where
-        F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         R: IntoLuaMulti<'lua>,
+        F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
     {
         WrappedFunction(Box::new(move |lua, args| {
             func(lua, A::from_lua_multi(args, lua)?)?.into_lua_multi(lua)
@@ -444,11 +594,11 @@ impl<'lua> Function<'lua> {
 
     /// Wraps a Rust mutable closure, returning an opaque type that implements [`IntoLua`] trait.
     #[inline]
-    pub fn wrap_mut<F, A, R>(func: F) -> impl IntoLua<'lua>
+    pub fn wrap_mut<A, R, F>(func: F) -> impl IntoLua<'lua>
     where
-        F: FnMut(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
         R: IntoLuaMulti<'lua>,
+        F: FnMut(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
     {
         let func = RefCell::new(func);
         WrappedFunction(Box::new(move |lua, args| {
@@ -459,14 +609,15 @@ impl<'lua> Function<'lua> {
         }))
     }
 
+    /// Wraps a Rust async function or closure, returning an opaque type that implements [`IntoLua`] trait.
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
-    pub fn wrap_async<F, A, FR, R>(func: F) -> impl IntoLua<'lua>
+    pub fn wrap_async<A, R, F, FR>(func: F) -> impl IntoLua<'lua>
     where
-        F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
         A: FromLuaMulti<'lua>,
-        FR: Future<Output = Result<R>> + 'lua,
         R: IntoLuaMulti<'lua>,
+        F: Fn(&'lua Lua, A) -> FR + MaybeSend + 'static,
+        FR: Future<Output = Result<R>> + 'lua,
     {
         WrappedAsyncFunction(Box::new(move |lua, args| {
             let args = match A::from_lua_multi(args, lua) {
@@ -484,6 +635,6 @@ mod assertions {
 
     static_assertions::assert_not_impl_any!(Function: Send);
 
-    #[cfg(feature = "unstable")]
+    #[cfg(all(feature = "unstable", not(feature = "send")))]
     static_assertions::assert_not_impl_any!(OwnedFunction: Send);
 }

src/hook.rs

@@ -3,7 +3,8 @@ use std::cell::UnsafeCell;
 use std::ops::{BitOr, BitOrAssign};
 use std::os::raw::c_int;
 
-use crate::ffi::{self, lua_Debug};
+use ffi::lua_Debug;
+
 use crate::lua::Lua;
 use crate::util::ptr_to_cstr_bytes;
 
@@ -266,48 +267,59 @@ pub struct HookTriggers {
 
 #[cfg(not(feature = "luau"))]
 impl HookTriggers {
-    /// Returns a new instance of `HookTriggers` with [`on_calls`] trigger set.
+    /// An instance of `HookTriggers` with `on_calls` trigger set.
+    pub const ON_CALLS: Self = HookTriggers::new().on_calls();
+
+    /// An instance of `HookTriggers` with `on_returns` trigger set.
+    pub const ON_RETURNS: Self = HookTriggers::new().on_returns();
+
+    /// An instance of `HookTriggers` with `every_line` trigger set.
+    pub const EVERY_LINE: Self = HookTriggers::new().every_line();
+
+    /// Returns a new instance of `HookTriggers` with all triggers disabled.
+    pub const fn new() -> Self {
+        HookTriggers {
+            on_calls: false,
+            on_returns: false,
+            every_line: false,
+            every_nth_instruction: None,
+        }
+    }
+
+    /// Returns an instance of `HookTriggers` with [`on_calls`] trigger set.
     ///
     /// [`on_calls`]: #structfield.on_calls
-    pub fn on_calls() -> Self {
-        HookTriggers {
-            on_calls: true,
-            ..Default::default()
-        }
+    pub const fn on_calls(mut self) -> Self {
+        self.on_calls = true;
+        self
     }
 
-    /// Returns a new instance of `HookTriggers` with [`on_returns`] trigger set.
+    /// Returns an instance of `HookTriggers` with [`on_returns`] trigger set.
     ///
     /// [`on_returns`]: #structfield.on_returns
-    pub fn on_returns() -> Self {
-        HookTriggers {
-            on_returns: true,
-            ..Default::default()
-        }
+    pub const fn on_returns(mut self) -> Self {
+        self.on_returns = true;
+        self
     }
 
-    /// Returns a new instance of `HookTriggers` with [`every_line`] trigger set.
+    /// Returns an instance of `HookTriggers` with [`every_line`] trigger set.
     ///
     /// [`every_line`]: #structfield.every_line
-    pub fn every_line() -> Self {
-        HookTriggers {
-            every_line: true,
-            ..Default::default()
-        }
+    pub const fn every_line(mut self) -> Self {
+        self.every_line = true;
+        self
     }
 
-    /// Returns a new instance of `HookTriggers` with [`every_nth_instruction`] trigger set.
+    /// Returns an instance of `HookTriggers` with [`every_nth_instruction`] trigger set.
     ///
     /// [`every_nth_instruction`]: #structfield.every_nth_instruction
-    pub fn every_nth_instruction(n: u32) -> Self {
-        HookTriggers {
-            every_nth_instruction: Some(n),
-            ..Default::default()
-        }
+    pub const fn every_nth_instruction(mut self, n: u32) -> Self {
+        self.every_nth_instruction = Some(n);
+        self
     }
 
     // Compute the mask to pass to `lua_sethook`.
-    pub(crate) fn mask(&self) -> c_int {
+    pub(crate) const fn mask(&self) -> c_int {
         let mut mask: c_int = 0;
         if self.on_calls {
             mask |= ffi::LUA_MASKCALL
@@ -326,8 +338,9 @@ impl HookTriggers {
 
     // Returns the `count` parameter to pass to `lua_sethook`, if applicable. Otherwise, zero is
     // returned.
-    pub(crate) fn count(&self) -> c_int {
-        self.every_nth_instruction.unwrap_or(0) as c_int
+    pub(crate) const fn count(&self) -> c_int {
+        let Some(n) = self.every_nth_instruction else { return 0 };
+        n as c_int
     }
 }
 

src/lib.rs

@@ -71,8 +71,6 @@
 //! [`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/0.9.0-beta.1")]
 // Deny warnings inside doc tests / examples. When this isn't present, rustdoc doesn't show *any*
 // warnings at all.
 #![doc(test(attr(deny(warnings))))]
@@ -84,7 +82,6 @@ mod macros;
 mod chunk;
 mod conversion;
 mod error;
-mod ffi;
 mod function;
 mod hook;
 mod lua;
@@ -106,7 +103,7 @@ mod value;
 
 pub mod prelude;
 
-pub use crate::{ffi::lua_CFunction, ffi::lua_State};
+pub use ffi::{lua_CFunction, lua_State};
 
 pub use crate::chunk::{AsChunk, Chunk, ChunkMode};
 pub use crate::error::{Error, ErrorContext, ExternalError, ExternalResult, Result};
@@ -119,7 +116,7 @@ pub use crate::stdlib::StdLib;
 pub use crate::string::String;
 pub use crate::table::{Table, TableExt, TablePairs, TableSequence};
 pub use crate::thread::{Thread, ThreadStatus};
-pub use crate::types::{Integer, LightUserData, Number, RegistryKey};
+pub use crate::types::{AppDataRef, AppDataRefMut, Integer, LightUserData, Number, RegistryKey};
 pub use crate::userdata::{
     AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMetatable, UserDataMethods,
     UserDataRef, UserDataRefMut,
@@ -148,14 +145,16 @@ pub use crate::serde::{
 #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
 pub mod serde;
 
-#[cfg(any(feature = "mlua_derive"))]
+#[cfg(feature = "mlua_derive")]
 #[allow(unused_imports)]
 #[macro_use]
 extern crate mlua_derive;
 
 // Unstable features
-#[cfg(all(feature = "unstable", not(feature = "send")))]
-pub use crate::{function::OwnedFunction, table::OwnedTable, userdata::OwnedAnyUserData};
+#[cfg(feature = "unstable")]
+pub use crate::{
+    function::OwnedFunction, string::OwnedString, table::OwnedTable, userdata::OwnedAnyUserData,
+};
 
 /// Create a type that implements [`AsChunk`] and can capture Rust variables.
 ///
@@ -209,7 +208,7 @@ pub use crate::{function::OwnedFunction, table::OwnedTable, userdata::OwnedAnyUs
 /// [`AsChunk`]: crate::AsChunk
 /// [`UserData`]: crate::UserData
 /// [`IntoLua`]: crate::IntoLua
-#[cfg(any(feature = "macros"))]
+#[cfg(feature = "macros")]
 #[cfg_attr(docsrs, doc(cfg(feature = "macros")))]
 pub use mlua_derive::chunk;
 

src/luau.rs

@@ -4,7 +4,6 @@ use std::string::String as StdString;
 
 use crate::chunk::ChunkMode;
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::lua::Lua;
 use crate::table::Table;
 use crate::util::{check_stack, StackGuard};
@@ -25,7 +24,7 @@ impl Lua {
 
         // Set `_VERSION` global to include version number
         // The environment variable `LUAU_VERSION` set by the build script
-        if let Some(version) = option_env!("LUAU_VERSION") {
+        if let Some(version) = ffi::luau_version() {
             globals.raw_set("_VERSION", format!("Luau {version}"))?;
         }
 

src/macros.rs

@@ -103,7 +103,12 @@ macro_rules! protect_lua {
     ($state:expr, $nargs:expr, $nresults:expr, fn($state_inner:ident) $code:expr) => {{
         unsafe extern "C" fn do_call($state_inner: *mut ffi::lua_State) -> ::std::os::raw::c_int {
             $code;
-            $nresults
+            let nresults = $nresults;
+            if nresults == ::ffi::LUA_MULTRET {
+                ffi::lua_gettop($state_inner)
+            } else {
+                nresults
+            }
         }
 
         crate::util::protect_lua_call($state, $nargs, do_call)

src/memory.rs

@@ -2,7 +2,6 @@ use std::alloc::{self, Layout};
 use std::os::raw::c_void;
 use std::ptr;
 
-use crate::ffi;
 #[cfg(feature = "luau")]
 use crate::lua::ExtraData;
 

src/prelude.rs

@@ -36,9 +36,9 @@ pub use crate::{
     SerializeOptions as LuaSerializeOptions,
 };
 
-#[cfg(all(feature = "unstable", not(feature = "send")))]
+#[cfg(feature = "unstable")]
 #[doc(no_inline)]
 pub use crate::{
     OwnedAnyUserData as LuaOwnedAnyUserData, OwnedFunction as LuaOwnedFunction,
-    OwnedTable as LuaOwnedTable,
+    OwnedString as LuaOwnedString, OwnedTable as LuaOwnedTable,
 };

src/scope.rs

@@ -8,13 +8,13 @@ use std::os::raw::c_int;
 use serde::Serialize;
 
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::function::Function;
 use crate::lua::Lua;
 use crate::types::{Callback, CallbackUpvalue, LuaRef, MaybeSend};
 use crate::userdata::{
     AnyUserData, MetaMethod, UserData, UserDataCell, UserDataFields, UserDataMethods,
 };
+use crate::userdata_impl::UserDataRegistrar;
 use crate::util::{
     assert_stack, check_stack, get_userdata, init_userdata_metatable, push_table, rawset_field,
     take_userdata, StackGuard,
@@ -25,7 +25,7 @@ use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, MultiValue, Val
 use crate::userdata::USER_VALUE_MAXSLOT;
 
 #[cfg(feature = "async")]
-use futures_core::future::Future;
+use std::future::Future;
 
 /// Constructed by the [`Lua::scope`] method, allows temporarily creating Lua userdata and
 /// callbacks that are not required to be Send or 'static.
@@ -33,7 +33,10 @@ use futures_core::future::Future;
 /// See [`Lua::scope`] for more details.
 ///
 /// [`Lua::scope`]: crate::Lua.html::scope
-pub struct Scope<'lua, 'scope> {
+pub struct Scope<'lua, 'scope>
+where
+    'lua: 'scope,
+{
     lua: &'lua Lua,
     destructors: RefCell<Vec<(LuaRef<'lua>, DestructorCallback<'lua>)>>,
     _scope_invariant: PhantomData<Cell<&'scope ()>>,
@@ -394,7 +397,7 @@ impl<'lua, 'scope> Scope<'lua, 'scope> {
                 rawset_field(state, -2, MetaMethod::validate(&k)?)?;
             }
             for (k, f) in ud_fields.meta_fields {
-                lua.push_value(f(mem::transmute(lua))?)?;
+                lua.push_value(f(lua, MultiValue::new())?.pop_front().unwrap())?;
                 rawset_field(state, -2, MetaMethod::validate(&k)?)?;
             }
             let metatable_index = ffi::lua_absindex(state, -1);
@@ -735,15 +738,16 @@ impl<'lua, T: UserData> UserDataMethods<'lua, T> for NonStaticUserDataMethods<'l
 }
 
 struct NonStaticUserDataFields<'lua, T: UserData> {
+    fields: Vec<(String, Callback<'lua, 'static>)>,
     field_getters: Vec<(String, NonStaticMethod<'lua, T>)>,
     field_setters: Vec<(String, NonStaticMethod<'lua, T>)>,
-    #[allow(clippy::type_complexity)]
-    meta_fields: Vec<(String, Box<dyn Fn(&'lua Lua) -> Result<Value<'lua>>>)>,
+    meta_fields: Vec<(String, Callback<'lua, 'static>)>,
 }
 
 impl<'lua, T: UserData> Default for NonStaticUserDataFields<'lua, T> {
     fn default() -> NonStaticUserDataFields<'lua, T> {
         NonStaticUserDataFields {
+            fields: Vec::new(),
             field_getters: Vec::new(),
             field_setters: Vec::new(),
             meta_fields: Vec::new(),
@@ -752,6 +756,17 @@ impl<'lua, T: UserData> Default for NonStaticUserDataFields<'lua, T> {
 }
 
 impl<'lua, T: UserData> UserDataFields<'lua, T> for NonStaticUserDataFields<'lua, T> {
+    fn add_field<V>(&mut self, name: impl AsRef<str>, value: V)
+    where
+        V: IntoLua<'lua> + Clone + 'static,
+    {
+        let name = name.as_ref().to_string();
+        self.fields.push((
+            name,
+            Box::new(move |lua, _| value.clone().into_lua_multi(lua)),
+        ));
+    }
+
     fn add_field_method_get<M, R>(&mut self, name: impl AsRef<str>, method: M)
     where
         M: Fn(&'lua Lua, &T) -> Result<R> + MaybeSend + 'static,
@@ -797,30 +812,30 @@ impl<'lua, T: UserData> UserDataFields<'lua, T> for NonStaticUserDataFields<'lua
         self.field_setters.push((name.as_ref().into(), func));
     }
 
+    fn add_meta_field<V>(&mut self, name: impl AsRef<str>, value: V)
+    where
+        V: IntoLua<'lua> + Clone + 'static,
+    {
+        let name = name.as_ref().to_string();
+        let name2 = name.clone();
+        self.meta_fields.push((
+            name,
+            Box::new(move |lua, _| {
+                UserDataRegistrar::<()>::check_meta_field(lua, &name2, value.clone())
+            }),
+        ));
+    }
+
     fn add_meta_field_with<F, R>(&mut self, name: impl AsRef<str>, f: F)
     where
         F: Fn(&'lua Lua) -> Result<R> + MaybeSend + 'static,
         R: IntoLua<'lua>,
     {
         let name = name.as_ref().to_string();
+        let name2 = name.clone();
         self.meta_fields.push((
-            name.clone(),
-            Box::new(move |lua| {
-                let value = f(lua)?.into_lua(lua)?;
-                if name == MetaMethod::Index || name == MetaMethod::NewIndex {
-                    match value {
-                        Value::Nil | Value::Table(_) | Value::Function(_) => {}
-                        _ => {
-                            return Err(Error::MetaMethodTypeError {
-                                method: name.clone(),
-                                type_name: value.type_name(),
-                                message: Some("expected nil, table or function".to_string()),
-                            })
-                        }
-                    }
-                }
-                Ok(value)
-            }),
+            name,
+            Box::new(move |lua, _| UserDataRegistrar::<()>::check_meta_field(lua, &name2, f(lua)?)),
         ));
     }
 }

src/serde/de.rs

@@ -345,9 +345,31 @@ impl<'lua, 'de> serde::Deserializer<'de> for Deserializer<'lua> {
         }
     }
 
+    #[inline]
+    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.value {
+            Value::LightUserData(ud) if ud.0.is_null() => visitor.visit_unit(),
+            _ => self.deserialize_any(visitor),
+        }
+    }
+
+    #[inline]
+    fn deserialize_unit_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: de::Visitor<'de>,
+    {
+        match self.value {
+            Value::LightUserData(ud) if ud.0.is_null() => visitor.visit_unit(),
+            _ => self.deserialize_any(visitor),
+        }
+    }
+
     serde::forward_to_deserialize_any! {
         bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string bytes
-        byte_buf unit unit_struct identifier ignored_any
+        byte_buf identifier ignored_any
     }
 }
 

src/serde/mod.rs

@@ -1,22 +1,19 @@
 //! (De)Serialization support using serde.
 
 use std::os::raw::c_void;
-use std::ptr;
 
-use serde::{Deserialize, Serialize};
+use serde::{de::DeserializeOwned, ser::Serialize};
 
 use crate::error::Result;
-use crate::ffi;
 use crate::lua::Lua;
 use crate::private::Sealed;
 use crate::table::Table;
-use crate::types::LightUserData;
 use crate::util::check_stack;
 use crate::value::Value;
 
 /// Trait for serializing/deserializing Lua values using Serde.
 #[cfg_attr(docsrs, doc(cfg(feature = "serialize")))]
-pub trait LuaSerdeExt<'lua>: Sealed {
+pub trait LuaSerdeExt: Sealed {
     /// A special value (lightuserdata) to encode/decode optional (none) values.
     ///
     /// Requires `feature = "serialize"`
@@ -38,7 +35,7 @@ pub trait LuaSerdeExt<'lua>: Sealed {
     ///     Ok(())
     /// }
     /// ```
-    fn null(&'lua self) -> Value<'lua>;
+    fn null(&self) -> Value;
 
     /// 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
@@ -69,7 +66,7 @@ pub trait LuaSerdeExt<'lua>: Sealed {
     ///     Ok(())
     /// }
     /// ```
-    fn array_metatable(&'lua self) -> Table<'lua>;
+    fn array_metatable(&self) -> Table;
 
     /// Converts `T` into a [`Value`] instance.
     ///
@@ -102,7 +99,7 @@ pub trait LuaSerdeExt<'lua>: Sealed {
     ///     "#).exec()
     /// }
     /// ```
-    fn to_value<T: Serialize + ?Sized>(&'lua self, t: &T) -> Result<Value<'lua>>;
+    fn to_value<'lua, T: Serialize + ?Sized>(&'lua self, t: &T) -> Result<Value<'lua>>;
 
     /// Converts `T` into a [`Value`] instance with options.
     ///
@@ -127,7 +124,7 @@ pub trait LuaSerdeExt<'lua>: Sealed {
     ///     "#).exec()
     /// }
     /// ```
-    fn to_value_with<T>(&'lua self, t: &T, options: ser::Options) -> Result<Value<'lua>>
+    fn to_value_with<'lua, T>(&'lua self, t: &T, options: ser::Options) -> Result<Value<'lua>>
     where
         T: Serialize + ?Sized;
 
@@ -160,7 +157,7 @@ pub trait LuaSerdeExt<'lua>: Sealed {
     /// }
     /// ```
     #[allow(clippy::wrong_self_convention)]
-    fn from_value<T: Deserialize<'lua>>(&'lua self, value: Value<'lua>) -> Result<T>;
+    fn from_value<T: DeserializeOwned>(&self, value: Value) -> Result<T>;
 
     /// Deserializes a [`Value`] into any serde deserializable object with options.
     ///
@@ -192,49 +189,46 @@ pub trait LuaSerdeExt<'lua>: Sealed {
     /// }
     /// ```
     #[allow(clippy::wrong_self_convention)]
-    fn from_value_with<T: Deserialize<'lua>>(
-        &'lua self,
-        value: Value<'lua>,
-        options: de::Options,
-    ) -> Result<T>;
+    fn from_value_with<T: DeserializeOwned>(&self, value: Value, options: de::Options)
+        -> Result<T>;
 }
 
-impl<'lua> LuaSerdeExt<'lua> for Lua {
-    fn null(&'lua self) -> Value<'lua> {
-        Value::LightUserData(LightUserData(ptr::null_mut()))
+impl LuaSerdeExt for Lua {
+    fn null(&self) -> Value {
+        Value::NULL
     }
 
-    fn array_metatable(&'lua self) -> Table<'lua> {
+    fn array_metatable(&self) -> Table {
         unsafe {
             push_array_metatable(self.ref_thread());
             Table(self.pop_ref_thread())
         }
     }
 
-    fn to_value<T>(&'lua self, t: &T) -> Result<Value<'lua>>
+    fn to_value<'lua, T>(&'lua self, t: &T) -> Result<Value<'lua>>
     where
         T: Serialize + ?Sized,
     {
         t.serialize(ser::Serializer::new(self))
     }
 
-    fn to_value_with<T>(&'lua self, t: &T, options: ser::Options) -> Result<Value<'lua>>
+    fn to_value_with<'lua, T>(&'lua self, t: &T, options: ser::Options) -> Result<Value<'lua>>
     where
         T: Serialize + ?Sized,
     {
         t.serialize(ser::Serializer::new_with_options(self, options))
     }
 
-    fn from_value<T>(&'lua self, value: Value<'lua>) -> Result<T>
+    fn from_value<T>(&self, value: Value) -> Result<T>
     where
-        T: Deserialize<'lua>,
+        T: DeserializeOwned,
     {
         T::deserialize(de::Deserializer::new(value))
     }
 
-    fn from_value_with<T>(&'lua self, value: Value<'lua>, options: de::Options) -> Result<T>
+    fn from_value_with<T>(&self, value: Value, options: de::Options) -> Result<T>
     where
-        T: Deserialize<'lua>,
+        T: DeserializeOwned,
     {
         T::deserialize(de::Deserializer::new_with_options(value, options))
     }

src/serde/ser.rs

@@ -4,7 +4,6 @@ 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;

src/string.rs

@@ -11,7 +11,6 @@ use {
 };
 
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::types::LuaRef;
 
 /// Handle to an internal Lua string.
@@ -20,6 +19,27 @@ use crate::types::LuaRef;
 #[derive(Clone)]
 pub struct String<'lua>(pub(crate) LuaRef<'lua>);
 
+/// Owned handle to an internal Lua string.
+///
+/// The owned handle holds a *strong* reference to the current Lua instance.
+/// Be warned, if you place it into a Lua type (eg. [`UserData`] or a Rust callback), it is *very easy*
+/// to accidentally cause reference cycles that would prevent destroying Lua instance.
+///
+/// [`UserData`]: crate::UserData
+#[cfg(feature = "unstable")]
+#[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
+#[derive(Clone)]
+pub struct OwnedString(pub(crate) crate::types::LuaOwnedRef);
+
+#[cfg(feature = "unstable")]
+impl OwnedString {
+    /// Get borrowed handle to the underlying Lua string.
+    #[cfg_attr(feature = "send", allow(unused))]
+    pub const fn to_ref(&self) -> String {
+        String(self.0.to_ref())
+    }
+}
+
 impl<'lua> String<'lua> {
     /// Get a `&str` slice if the Lua string is valid UTF-8.
     ///
@@ -122,6 +142,14 @@ impl<'lua> String<'lua> {
         let ref_thread = self.0.lua.ref_thread();
         unsafe { ffi::lua_topointer(ref_thread, self.0.index) }
     }
+
+    /// Convert this handle to owned version.
+    #[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
+    #[inline]
+    pub fn into_owned(self) -> OwnedString {
+        OwnedString(self.0.into_owned())
+    }
 }
 
 impl<'lua> fmt::Debug for String<'lua> {
@@ -203,6 +231,37 @@ impl<'lua> Serialize for String<'lua> {
     }
 }
 
+// Additional shortcuts
+#[cfg(feature = "unstable")]
+impl OwnedString {
+    /// Get a `&str` slice if the Lua string is valid UTF-8.
+    ///
+    /// This is a shortcut for [`String::to_str()`].
+    #[inline]
+    pub fn to_str(&self) -> Result<&str> {
+        let s = self.to_ref();
+        // Reattach lifetime to &self
+        unsafe { std::mem::transmute(s.to_str()) }
+    }
+
+    /// Get the bytes that make up this string.
+    ///
+    /// This is a shortcut for [`String::as_bytes()`].
+    #[inline]
+    pub fn as_bytes(&self) -> &[u8] {
+        let s = self.to_ref();
+        // Reattach lifetime to &self
+        unsafe { std::mem::transmute(s.as_bytes()) }
+    }
+}
+
+#[cfg(feature = "unstable")]
+impl fmt::Debug for OwnedString {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.to_ref().fmt(f)
+    }
+}
+
 #[cfg(test)]
 mod assertions {
     use super::*;

src/table.rs

@@ -1,3 +1,5 @@
+use std::collections::HashSet;
+use std::fmt;
 use std::marker::PhantomData;
 use std::os::raw::c_void;
 
@@ -9,7 +11,6 @@ use {
 };
 
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::function::Function;
 use crate::private::Sealed;
 use crate::types::{Integer, LuaRef};
@@ -17,13 +18,19 @@ use crate::util::{assert_stack, check_stack, StackGuard};
 use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Nil, Value};
 
 #[cfg(feature = "async")]
-use {futures_core::future::LocalBoxFuture, futures_util::future};
+use futures_util::future::{self, LocalBoxFuture};
 
 /// Handle to an internal Lua table.
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct Table<'lua>(pub(crate) LuaRef<'lua>);
 
 /// Owned handle to an internal Lua table.
+///
+/// The owned handle holds a *strong* reference to the current Lua instance.
+/// Be warned, if you place it into a Lua type (eg. [`UserData`] or a Rust callback), it is *very easy*
+/// to accidentally cause reference cycles that would prevent destroying Lua instance.
+///
+/// [`UserData`]: crate::UserData
 #[cfg(feature = "unstable")]
 #[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
 #[derive(Clone, Debug)]
@@ -32,6 +39,7 @@ pub struct OwnedTable(pub(crate) crate::types::LuaOwnedRef);
 #[cfg(feature = "unstable")]
 impl OwnedTable {
     /// Get borrowed handle to the underlying Lua table.
+    #[cfg_attr(feature = "send", allow(unused))]
     pub const fn to_ref(&self) -> Table {
         Table(self.0.to_ref())
     }
@@ -583,8 +591,8 @@ impl<'lua> Table<'lua> {
     }
 
     /// Convert this handle to owned version.
-    #[cfg(feature = "unstable")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
+    #[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
     #[inline]
     pub fn into_owned(self) -> OwnedTable {
         OwnedTable(self.0.into_owned())
@@ -697,7 +705,7 @@ impl<'lua> Table<'lua> {
         }
     }
 
-    #[cfg(any(feature = "serialize"))]
+    #[cfg(feature = "serialize")]
     pub(crate) fn raw_sequence_values_by_len<V: FromLua<'lua>>(
         self,
         len: Option<Integer>,
@@ -738,6 +746,42 @@ impl<'lua> Table<'lua> {
         }
         Ok(())
     }
+
+    pub(crate) fn fmt_pretty(
+        &self,
+        fmt: &mut fmt::Formatter,
+        ident: usize,
+        visited: &mut HashSet<*const c_void>,
+    ) -> fmt::Result {
+        visited.insert(self.to_pointer());
+
+        let t = self.clone();
+        // Collect key/value pairs into a vector so we can sort them
+        let mut pairs = t.pairs::<Value, Value>().flatten().collect::<Vec<_>>();
+        // Sort keys
+        pairs.sort_by(|(a, _), (b, _)| a.cmp(b));
+        if pairs.is_empty() {
+            return write!(fmt, "{{}}");
+        }
+        writeln!(fmt, "{{")?;
+        for (key, value) in pairs {
+            write!(fmt, "{}[", " ".repeat(ident + 2))?;
+            key.fmt_pretty(fmt, false, ident + 2, visited)?;
+            write!(fmt, "] = ")?;
+            value.fmt_pretty(fmt, true, ident + 2, visited)?;
+            writeln!(fmt, ",")?;
+        }
+        write!(fmt, "{}}}", " ".repeat(ident))
+    }
+}
+
+impl fmt::Debug for Table<'_> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        if fmt.alternate() {
+            return self.fmt_pretty(fmt, 0, &mut HashSet::new());
+        }
+        fmt.write_fmt(format_args!("Table({:?})", self.0))
+    }
 }
 
 impl<'lua> PartialEq for Table<'lua> {

src/thread.rs

@@ -2,7 +2,8 @@ use std::cmp;
 use std::os::raw::c_int;
 
 use crate::error::{Error, Result};
-use crate::ffi;
+#[allow(unused)]
+use crate::lua::Lua;
 use crate::types::LuaRef;
 use crate::util::{check_stack, error_traceback_thread, pop_error, StackGuard};
 use crate::value::{FromLuaMulti, IntoLuaMulti};
@@ -14,14 +15,21 @@ use crate::value::{FromLuaMulti, IntoLuaMulti};
 ))]
 use crate::function::Function;
 
+#[cfg(not(feature = "luau"))]
+use crate::{
+    hook::{Debug, HookTriggers},
+    types::MaybeSend,
+};
+
 #[cfg(feature = "async")]
 use {
     crate::{
-        lua::{Lua, ASYNC_POLL_PENDING},
+        lua::ASYNC_POLL_PENDING,
         value::{MultiValue, Value},
     },
-    futures_core::{future::Future, stream::Stream},
+    futures_util::stream::Stream,
     std::{
+        future::Future,
         marker::PhantomData,
         pin::Pin,
         ptr::NonNull,
@@ -56,6 +64,7 @@ pub struct Thread<'lua>(pub(crate) LuaRef<'lua>);
 /// [`Stream`]: futures_core::stream::Stream
 #[cfg(feature = "async")]
 #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct AsyncThread<'lua, R> {
     thread: Thread<'lua>,
     args0: Option<Result<MultiValue<'lua>>>,
@@ -177,6 +186,23 @@ impl<'lua> Thread<'lua> {
         }
     }
 
+    /// Sets a 'hook' function that will periodically be called as Lua code executes.
+    ///
+    /// This function is similar or [`Lua::set_hook()`] except that it sets for the thread.
+    /// To remove a hook call [`Lua::remove_hook()`].
+    #[cfg(not(feature = "luau"))]
+    #[cfg_attr(docsrs, doc(cfg(not(feature = "luau"))))]
+    pub fn set_hook<F>(&self, triggers: HookTriggers, callback: F)
+    where
+        F: Fn(&Lua, Debug) -> Result<()> + MaybeSend + 'static,
+    {
+        let lua = self.0.lua;
+        unsafe {
+            let thread_state = ffi::lua_tothread(lua.ref_thread(), self.0.index);
+            lua.set_thread_hook(thread_state, triggers, callback);
+        }
+    }
+
     /// Resets a thread
     ///
     /// In [Lua 5.4]: cleans its call stack and closes all pending to-be-closed variables.
@@ -207,8 +233,10 @@ impl<'lua> Thread<'lua> {
             lua.push_ref(&self.0);
             let thread_state = ffi::lua_tothread(state, -1);
 
-            #[cfg(feature = "lua54")]
+            #[cfg(all(feature = "lua54", not(feature = "vendored")))]
             let status = ffi::lua_resetthread(thread_state);
+            #[cfg(all(feature = "lua54", feature = "vendored"))]
+            let status = ffi::lua_closethread(thread_state, state);
             #[cfg(feature = "lua54")]
             if status != ffi::LUA_OK {
                 return Err(pop_error(thread_state, status));
@@ -223,8 +251,8 @@ impl<'lua> Thread<'lua> {
 
             #[cfg(feature = "luau")]
             {
-                // Inherit `LUA_GLOBALSINDEX` from the caller
-                ffi::lua_xpush(state, thread_state, ffi::LUA_GLOBALSINDEX);
+                // Inherit `LUA_GLOBALSINDEX` from the main thread
+                ffi::lua_xpush(lua.main_state(), thread_state, ffi::LUA_GLOBALSINDEX);
                 ffi::lua_replace(thread_state, ffi::LUA_GLOBALSINDEX);
             }
 
@@ -332,11 +360,8 @@ impl<'lua> Thread<'lua> {
         let state = lua.state();
         unsafe {
             let thread = ffi::lua_tothread(lua.ref_thread(), self.0.index);
-            check_stack(thread, 1)?;
+            check_stack(thread, 3)?;
             check_stack(state, 3)?;
-            // Inherit `LUA_GLOBALSINDEX` from the caller
-            ffi::lua_xpush(state, thread, ffi::LUA_GLOBALSINDEX);
-            ffi::lua_replace(thread, ffi::LUA_GLOBALSINDEX);
             protect_lua!(state, 0, 0, |_| ffi::luaL_sandboxthread(thread))
         }
     }
@@ -372,7 +397,10 @@ impl<'lua, R> Drop for AsyncThread<'lua, R> {
                     #[cfg(feature = "lua54")]
                     if self.thread.status() == ThreadStatus::Error {
                         let thread_state = ffi::lua_tothread(lua.ref_thread(), self.thread.0.index);
+                        #[cfg(not(feature = "vendored"))]
                         ffi::lua_resetthread(thread_state);
+                        #[cfg(feature = "vendored")]
+                        ffi::lua_closethread(thread_state, lua.state());
                     }
                 }
             }

src/types.rs

@@ -1,6 +1,9 @@
-use std::cell::UnsafeCell;
+use std::any::{Any, TypeId};
+use std::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};
 use std::hash::{Hash, Hasher};
+use std::ops::{Deref, DerefMut};
 use std::os::raw::{c_int, c_void};
+use std::result::Result as StdResult;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use std::{fmt, mem, ptr};
@@ -8,17 +11,21 @@ use std::{fmt, mem, ptr};
 #[cfg(feature = "lua54")]
 use std::ffi::CStr;
 
+use rustc_hash::FxHashMap;
+
 #[cfg(feature = "async")]
-use futures_core::future::LocalBoxFuture;
+use futures_util::future::LocalBoxFuture;
 
 use crate::error::Result;
-use crate::ffi;
 #[cfg(not(feature = "luau"))]
 use crate::hook::Debug;
 use crate::lua::{ExtraData, Lua};
 use crate::util::{assert_stack, StackGuard};
 use crate::value::MultiValue;
 
+#[cfg(feature = "unstable")]
+use {crate::lua::LuaInner, std::marker::PhantomData};
+
 /// Type of Lua integer numbers.
 pub type Integer = ffi::lua_Integer;
 /// Type of Lua floating point numbers.
@@ -238,9 +245,9 @@ impl<'lua> PartialEq for LuaRef<'lua> {
 
 #[cfg(feature = "unstable")]
 pub(crate) struct LuaOwnedRef {
-    pub(crate) lua: Lua,
+    pub(crate) inner: Arc<LuaInner>,
     pub(crate) index: c_int,
-    _non_send: std::marker::PhantomData<*const ()>,
+    _non_send: PhantomData<*const ()>,
 }
 
 #[cfg(feature = "unstable")]
@@ -260,37 +267,174 @@ impl Clone for LuaOwnedRef {
 #[cfg(feature = "unstable")]
 impl Drop for LuaOwnedRef {
     fn drop(&mut self) {
-        self.lua.drop_ref_index(self.index);
+        let lua: &Lua = unsafe { mem::transmute(&self.inner) };
+        lua.drop_ref_index(self.index);
     }
 }
 
 #[cfg(feature = "unstable")]
 impl LuaOwnedRef {
-    pub(crate) const fn new(lua: Lua, index: c_int) -> Self {
-        #[cfg(feature = "send")]
-        {
-            let _lua = lua;
-            let _index = index;
-            panic!("mlua must be compiled without \"send\" feature to use Owned types");
-        }
-
-        #[cfg(not(feature = "send"))]
+    pub(crate) const fn new(inner: Arc<LuaInner>, index: c_int) -> Self {
         LuaOwnedRef {
-            lua,
+            inner,
             index,
-            _non_send: std::marker::PhantomData,
+            _non_send: PhantomData,
         }
     }
 
     pub(crate) const fn to_ref(&self) -> LuaRef {
         LuaRef {
-            lua: &self.lua,
+            lua: unsafe { mem::transmute(&self.inner) },
             index: self.index,
             drop: false,
         }
     }
 }
 
+#[derive(Debug, Default)]
+pub(crate) struct AppData {
+    #[cfg(not(feature = "send"))]
+    container: UnsafeCell<FxHashMap<TypeId, RefCell<Box<dyn Any>>>>,
+    #[cfg(feature = "send")]
+    container: UnsafeCell<FxHashMap<TypeId, RefCell<Box<dyn Any + Send>>>>,
+    borrow: Cell<usize>,
+}
+
+impl AppData {
+    #[track_caller]
+    pub(crate) fn insert<T: MaybeSend + 'static>(&self, data: T) -> Option<T> {
+        match self.try_insert(data) {
+            Ok(data) => data,
+            Err(_) => panic!("cannot mutably borrow app data container"),
+        }
+    }
+
+    pub(crate) fn try_insert<T: MaybeSend + 'static>(&self, data: T) -> StdResult<Option<T>, T> {
+        if self.borrow.get() != 0 {
+            return Err(data);
+        }
+        // SAFETY: we checked that there are no other references to the container
+        Ok(unsafe { &mut *self.container.get() }
+            .insert(TypeId::of::<T>(), RefCell::new(Box::new(data)))
+            .and_then(|data| data.into_inner().downcast::<T>().ok().map(|data| *data)))
+    }
+
+    #[track_caller]
+    pub(crate) fn borrow<T: 'static>(&self) -> Option<AppDataRef<T>> {
+        let data = unsafe { &*self.container.get() }
+            .get(&TypeId::of::<T>())?
+            .borrow();
+        self.borrow.set(self.borrow.get() + 1);
+        Some(AppDataRef {
+            data: Ref::filter_map(data, |data| data.downcast_ref()).ok()?,
+            borrow: &self.borrow,
+        })
+    }
+
+    #[track_caller]
+    pub(crate) fn borrow_mut<T: 'static>(&self) -> Option<AppDataRefMut<T>> {
+        let data = unsafe { &*self.container.get() }
+            .get(&TypeId::of::<T>())?
+            .borrow_mut();
+        self.borrow.set(self.borrow.get() + 1);
+        Some(AppDataRefMut {
+            data: RefMut::filter_map(data, |data| data.downcast_mut()).ok()?,
+            borrow: &self.borrow,
+        })
+    }
+
+    #[track_caller]
+    pub(crate) fn remove<T: 'static>(&self) -> Option<T> {
+        if self.borrow.get() != 0 {
+            panic!("cannot mutably borrow app data container");
+        }
+        // SAFETY: we checked that there are no other references to the container
+        unsafe { &mut *self.container.get() }
+            .remove(&TypeId::of::<T>())?
+            .into_inner()
+            .downcast::<T>()
+            .ok()
+            .map(|data| *data)
+    }
+}
+
+/// A wrapper type for an immutably borrowed value from an app data container.
+///
+/// This type is similar to [`Ref`].
+pub struct AppDataRef<'a, T: ?Sized + 'a> {
+    data: Ref<'a, T>,
+    borrow: &'a Cell<usize>,
+}
+
+impl<T: ?Sized> Drop for AppDataRef<'_, T> {
+    fn drop(&mut self) {
+        self.borrow.set(self.borrow.get() - 1);
+    }
+}
+
+impl<T: ?Sized> Deref for AppDataRef<'_, T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+
+impl<T: ?Sized + fmt::Display> fmt::Display for AppDataRef<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T: ?Sized + fmt::Debug> fmt::Debug for AppDataRef<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+/// A wrapper type for a mutably borrowed value from an app data container.
+///
+/// This type is similar to [`RefMut`].
+pub struct AppDataRefMut<'a, T: ?Sized + 'a> {
+    data: RefMut<'a, T>,
+    borrow: &'a Cell<usize>,
+}
+
+impl<T: ?Sized> Drop for AppDataRefMut<'_, T> {
+    fn drop(&mut self) {
+        self.borrow.set(self.borrow.get() - 1);
+    }
+}
+
+impl<T: ?Sized> Deref for AppDataRefMut<'_, T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.data
+    }
+}
+
+impl<T: ?Sized> DerefMut for AppDataRefMut<'_, T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.data
+    }
+}
+
+impl<T: ?Sized + fmt::Display> fmt::Display for AppDataRefMut<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<T: ?Sized + fmt::Debug> fmt::Debug for AppDataRefMut<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
 #[cfg(test)]
 mod assertions {
     use super::*;

src/userdata.rs

@@ -17,16 +17,14 @@ use {
 };
 
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::function::Function;
 use crate::lua::Lua;
+use crate::string::String;
 use crate::table::{Table, TablePairs};
-use crate::types::{Callback, LuaRef, MaybeSend};
+use crate::types::{LuaRef, MaybeSend};
 use crate::util::{check_stack, get_userdata, take_userdata, StackGuard};
 use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
-
-#[cfg(feature = "async")]
-use crate::types::AsyncCallback;
+use crate::UserDataRegistrar;
 
 #[cfg(feature = "lua54")]
 pub(crate) const USER_VALUE_MAXSLOT: usize = 8;
@@ -140,7 +138,8 @@ pub enum MetaMethod {
     /// Requires `feature = "lua54"`
     ///
     /// [lua_doc]: https://www.lua.org/manual/5.4/manual.html#3.3.8
-    #[cfg(any(feature = "lua54"))]
+    #[cfg(feature = "lua54")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "lua54")))]
     Close,
 }
 
@@ -150,7 +149,7 @@ impl PartialEq<MetaMethod> for &str {
     }
 }
 
-impl PartialEq<MetaMethod> for String {
+impl PartialEq<MetaMethod> for StdString {
     fn eq(&self, other: &MetaMethod) -> bool {
         self == other.name()
     }
@@ -411,24 +410,26 @@ pub trait UserDataMethods<'lua, T> {
     //
 
     #[doc(hidden)]
-    fn add_callback(&mut self, _name: String, _callback: Callback<'lua, 'static>) {}
-
-    #[doc(hidden)]
-    #[cfg(feature = "async")]
-    fn add_async_callback(&mut self, _name: String, _callback: AsyncCallback<'lua, 'static>) {}
-
-    #[doc(hidden)]
-    fn add_meta_callback(&mut self, _name: String, _callback: Callback<'lua, 'static>) {}
-
-    #[doc(hidden)]
-    #[cfg(feature = "async")]
-    fn add_async_meta_callback(&mut self, _name: String, _callback: AsyncCallback<'lua, 'static>) {}
+    fn append_methods_from<S>(&mut self, _other: UserDataRegistrar<'lua, S>) {}
 }
 
 /// Field registry for [`UserData`] implementors.
 ///
 /// [`UserData`]: crate::UserData
 pub trait UserDataFields<'lua, T> {
+    /// Add a static field to the `UserData`.
+    ///
+    /// Static fields are implemented by updating the `__index` metamethod and returning the
+    /// accessed field. This allows them to be used with the expected `userdata.field` syntax.
+    ///
+    /// Static fields are usually shared between all instances of the `UserData` of the same type.
+    ///
+    /// If `add_meta_method` is used to set the `__index` metamethod, it will
+    /// be used as a fall-back if no regular field or method are found.
+    fn add_field<V>(&mut self, name: impl AsRef<str>, value: V)
+    where
+        V: IntoLua<'lua> + Clone + 'static;
+
     /// Add a regular field getter as a method which accepts a `&T` as the parameter.
     ///
     /// Regular field getters are implemented by overriding the `__index` metamethod and returning the
@@ -477,9 +478,21 @@ pub trait UserDataFields<'lua, T> {
         F: FnMut(&'lua Lua, AnyUserData<'lua>, A) -> Result<()> + MaybeSend + 'static,
         A: FromLua<'lua>;
 
-    /// Add a metamethod value computed from `f`.
+    /// Add a metatable field.
     ///
-    /// This will initialize the metamethod value from `f` on `UserData` creation.
+    /// This will initialize the metatable field with `value` on `UserData` creation.
+    ///
+    /// # Note
+    ///
+    /// `mlua` will trigger an error on an attempt to define a protected metamethod,
+    /// like `__gc` or `__metatable`.
+    fn add_meta_field<V>(&mut self, name: impl AsRef<str>, value: V)
+    where
+        V: IntoLua<'lua> + Clone + 'static;
+
+    /// Add a metatable field computed from `f`.
+    ///
+    /// This will initialize the metatable field from `f` on `UserData` creation.
     ///
     /// # Note
     ///
@@ -495,10 +508,7 @@ pub trait UserDataFields<'lua, T> {
     //
 
     #[doc(hidden)]
-    fn add_field_getter(&mut self, _name: String, _callback: Callback<'lua, 'static>) {}
-
-    #[doc(hidden)]
-    fn add_field_setter(&mut self, _name: String, _callback: Callback<'lua, 'static>) {}
+    fn append_fields_from<S>(&mut self, _other: UserDataRegistrar<'lua, S>) {}
 }
 
 /// Trait for custom userdata types.
@@ -740,6 +750,11 @@ impl Serialize for UserDataSerializeError {
 #[derive(Clone, Debug)]
 pub struct AnyUserData<'lua>(pub(crate) LuaRef<'lua>);
 
+/// Owned handle to an internal Lua userdata.
+///
+/// The owned handle holds a *strong* reference to the current Lua instance.
+/// Be warned, if you place it into a Lua type (eg. [`UserData`] or a Rust callback), it is *very easy*
+/// to accidentally cause reference cycles that would prevent destroying Lua instance.
 #[cfg(feature = "unstable")]
 #[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
 #[derive(Clone, Debug)]
@@ -747,6 +762,8 @@ pub struct OwnedAnyUserData(pub(crate) crate::types::LuaOwnedRef);
 
 #[cfg(feature = "unstable")]
 impl OwnedAnyUserData {
+    /// Get borrowed handle to the underlying Lua userdata.
+    #[cfg_attr(feature = "send", allow(unused))]
     pub const fn to_ref(&self) -> AnyUserData {
         AnyUserData(self.0.to_ref())
     }
@@ -1030,13 +1047,38 @@ impl<'lua> AnyUserData<'lua> {
         }
     }
 
-    #[cfg(feature = "unstable")]
-    #[cfg_attr(docsrs, doc(cfg(feature = "unstable")))]
+    /// Convert this handle to owned version.
+    #[cfg(all(feature = "unstable", any(not(feature = "send"), doc)))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "unstable", not(feature = "send")))))]
     #[inline]
     pub fn into_owned(self) -> OwnedAnyUserData {
         OwnedAnyUserData(self.0.into_owned())
     }
 
+    /// Returns a type name of this `UserData` (from `__name` metatable field).
+    pub(crate) fn type_name(&self) -> Result<Option<StdString>> {
+        let lua = self.0.lua;
+        let state = lua.state();
+        unsafe {
+            let _sg = StackGuard::new(state);
+            check_stack(state, 3)?;
+
+            lua.push_userdata_ref(&self.0)?;
+            let protect = !lua.unlikely_memory_error();
+            let name_type = if protect {
+                protect_lua!(state, 1, 1, |state| {
+                    ffi::luaL_getmetafield(state, -1, cstr!("__name"))
+                })?
+            } else {
+                ffi::luaL_getmetafield(state, -1, cstr!("__name"))
+            };
+            match name_type {
+                ffi::LUA_TSTRING => Ok(Some(String(lua.pop_ref()).to_str()?.to_owned())),
+                _ => Ok(None),
+            }
+        }
+    }
+
     pub(crate) fn equals<T: AsRef<Self>>(&self, other: T) -> Result<bool> {
         let other = other.as_ref();
         // Uses lua_rawequal() under the hood
@@ -1121,6 +1163,40 @@ unsafe fn getuservalue_table(state: *mut ffi::lua_State, idx: c_int) -> c_int {
     return ffi::lua_getuservalue(state, idx);
 }
 
+// Additional shortcuts
+#[cfg(feature = "unstable")]
+impl OwnedAnyUserData {
+    /// Borrow this userdata immutably if it is of type `T`.
+    ///
+    /// This is a shortcut for [`AnyUserData::borrow()`]
+    #[inline]
+    pub fn borrow<T: 'static>(&self) -> Result<Ref<T>> {
+        let ud = self.to_ref();
+        let t = ud.borrow::<T>()?;
+        // Reattach lifetime to &self
+        Ok(unsafe { mem::transmute::<Ref<T>, Ref<T>>(t) })
+    }
+
+    /// Borrow this userdata mutably if it is of type `T`.
+    ///
+    /// This is a shortcut for [`AnyUserData::borrow_mut()`]
+    #[inline]
+    pub fn borrow_mut<T: 'static>(&self) -> Result<RefMut<T>> {
+        let ud = self.to_ref();
+        let t = ud.borrow_mut::<T>()?;
+        // Reattach lifetime to &self
+        Ok(unsafe { mem::transmute::<RefMut<T>, RefMut<T>>(t) })
+    }
+
+    /// Takes the value out of this userdata.
+    ///
+    /// This is a shortcut for [`AnyUserData::take()`]
+    #[inline]
+    pub fn take<T: 'static>(&self) -> Result<T> {
+        self.to_ref().take()
+    }
+}
+
 /// Handle to a `UserData` metatable.
 #[derive(Clone, Debug)]
 pub struct UserDataMetatable<'lua>(pub(crate) Table<'lua>);
@@ -1178,7 +1254,7 @@ impl<'lua, V> Iterator for UserDataMetatablePairs<'lua, V>
 where
     V: FromLua<'lua>,
 {
-    type Item = Result<(String, V)>;
+    type Item = Result<(StdString, V)>;
 
     fn next(&mut self) -> Option<Self::Item> {
         loop {
@@ -1286,6 +1362,6 @@ mod assertions {
 
     static_assertions::assert_not_impl_any!(AnyUserData: Send);
 
-    #[cfg(feature = "unstable")]
+    #[cfg(all(feature = "unstable", not(feature = "send")))]
     static_assertions::assert_not_impl_any!(OwnedAnyUserData: Send);
 }

src/userdata_ext.rs

@@ -4,7 +4,7 @@ use crate::userdata::{AnyUserData, MetaMethod};
 use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
 
 #[cfg(feature = "async")]
-use {futures_core::future::LocalBoxFuture, futures_util::future};
+use futures_util::future::{self, LocalBoxFuture};
 
 /// An extension trait for [`AnyUserData`] that provides a variety of convenient functionality.
 pub trait AnyUserDataExt<'lua>: Sealed {

src/userdata_impl.rs

@@ -1,18 +1,17 @@
-use std::any::{self, TypeId};
+use std::any::TypeId;
 use std::cell::{Ref, RefCell, RefMut};
 use std::marker::PhantomData;
 use std::string::String as StdString;
 use std::sync::{Arc, Mutex, RwLock};
 
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::lua::Lua;
 use crate::types::{Callback, MaybeSend};
 use crate::userdata::{
     AnyUserData, MetaMethod, UserData, UserDataCell, UserDataFields, UserDataMethods,
 };
-use crate::util::{check_stack, get_userdata, StackGuard};
-use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
+use crate::util::{check_stack, get_userdata, short_type_name, StackGuard};
+use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, MultiValue, Value};
 
 #[cfg(not(feature = "send"))]
 use std::rc::Rc;
@@ -26,13 +25,10 @@ use {
 
 pub struct UserDataRegistrar<'lua, T: 'static> {
     // Fields
+    pub(crate) fields: Vec<(String, Callback<'lua, 'static>)>,
     pub(crate) field_getters: Vec<(String, Callback<'lua, 'static>)>,
     pub(crate) field_setters: Vec<(String, Callback<'lua, 'static>)>,
-    #[allow(clippy::type_complexity)]
-    pub(crate) meta_fields: Vec<(
-        String,
-        Box<dyn Fn(&'lua Lua) -> Result<Value<'lua>> + 'static>,
-    )>,
+    pub(crate) meta_fields: Vec<(String, Callback<'lua, 'static>)>,
 
     // Methods
     pub(crate) methods: Vec<(String, Callback<'lua, 'static>)>,
@@ -48,6 +44,7 @@ pub struct UserDataRegistrar<'lua, T: 'static> {
 impl<'lua, T: 'static> UserDataRegistrar<'lua, T> {
     pub(crate) const fn new() -> Self {
         UserDataRegistrar {
+            fields: Vec::new(),
             field_getters: Vec::new(),
             field_setters: Vec::new(),
             meta_fields: Vec::new(),
@@ -361,15 +358,49 @@ impl<'lua, T: 'static> UserDataRegistrar<'lua, T> {
             )
         })
     }
+
+    pub(crate) fn check_meta_field<V>(
+        lua: &'lua Lua,
+        name: &str,
+        value: V,
+    ) -> Result<MultiValue<'lua>>
+    where
+        V: IntoLua<'lua>,
+    {
+        let value = value.into_lua(lua)?;
+        if name == MetaMethod::Index || name == MetaMethod::NewIndex {
+            match value {
+                Value::Nil | Value::Table(_) | Value::Function(_) => {}
+                _ => {
+                    return Err(Error::MetaMethodTypeError {
+                        method: name.to_string(),
+                        type_name: value.type_name(),
+                        message: Some("expected nil, table or function".to_string()),
+                    })
+                }
+            }
+        }
+        value.into_lua_multi(lua)
+    }
 }
 
 // Returns function name for the type `T`, without the module path
-fn get_function_name<T: 'static>(name: &str) -> StdString {
-    let type_name = any::type_name::<T>().rsplit("::").next().unwrap();
-    format!("{type_name}.{name}",)
+fn get_function_name<T>(name: &str) -> StdString {
+    format!("{}.{name}", short_type_name::<T>())
 }
 
 impl<'lua, T: 'static> UserDataFields<'lua, T> for UserDataRegistrar<'lua, T> {
+    fn add_field<V>(&mut self, name: impl AsRef<str>, value: V)
+    where
+        V: IntoLua<'lua> + Clone + 'static,
+    {
+        let name = name.as_ref().to_string();
+        self.fields.push((
+            name,
+            Box::new(move |lua, _| value.clone().into_lua_multi(lua)),
+        ));
+    }
+
     fn add_field_method_get<M, R>(&mut self, name: impl AsRef<str>, method: M)
     where
         M: Fn(&'lua Lua, &T) -> Result<R> + MaybeSend + 'static,
@@ -410,41 +441,38 @@ impl<'lua, T: 'static> UserDataFields<'lua, T> for UserDataRegistrar<'lua, T> {
         self.field_setters.push((name.into(), func));
     }
 
+    fn add_meta_field<V>(&mut self, name: impl AsRef<str>, value: V)
+    where
+        V: IntoLua<'lua> + Clone + 'static,
+    {
+        let name = name.as_ref().to_string();
+        let name2 = name.clone();
+        self.meta_fields.push((
+            name,
+            Box::new(move |lua, _| Self::check_meta_field(lua, &name2, value.clone())),
+        ));
+    }
+
     fn add_meta_field_with<F, R>(&mut self, name: impl AsRef<str>, f: F)
     where
         F: Fn(&'lua Lua) -> Result<R> + MaybeSend + 'static,
         R: IntoLua<'lua>,
     {
         let name = name.as_ref().to_string();
+        let name2 = name.clone();
         self.meta_fields.push((
-            name.clone(),
-            Box::new(move |lua| {
-                let value = f(lua)?.into_lua(lua)?;
-                if name == MetaMethod::Index || name == MetaMethod::NewIndex {
-                    match value {
-                        Value::Nil | Value::Table(_) | Value::Function(_) => {}
-                        _ => {
-                            return Err(Error::MetaMethodTypeError {
-                                method: name.clone(),
-                                type_name: value.type_name(),
-                                message: Some("expected nil, table or function".to_string()),
-                            })
-                        }
-                    }
-                }
-                Ok(value)
-            }),
+            name,
+            Box::new(move |lua, _| Self::check_meta_field(lua, &name2, f(lua)?)),
         ));
     }
 
     // Below are internal methods
 
-    fn add_field_getter(&mut self, name: String, callback: Callback<'lua, 'static>) {
-        self.field_getters.push((name, callback));
-    }
-
-    fn add_field_setter(&mut self, name: String, callback: Callback<'lua, 'static>) {
-        self.field_setters.push((name, callback));
+    fn append_fields_from<S>(&mut self, other: UserDataRegistrar<'lua, S>) {
+        self.fields.extend(other.fields);
+        self.field_getters.extend(other.field_getters);
+        self.field_setters.extend(other.field_setters);
+        self.meta_fields.extend(other.meta_fields);
     }
 }
 
@@ -593,22 +621,13 @@ impl<'lua, T: 'static> UserDataMethods<'lua, T> for UserDataRegistrar<'lua, T> {
 
     // Below are internal methods used in generated code
 
-    fn add_callback(&mut self, name: String, callback: Callback<'lua, 'static>) {
-        self.methods.push((name, callback));
-    }
-
-    #[cfg(feature = "async")]
-    fn add_async_callback(&mut self, name: String, callback: AsyncCallback<'lua, 'static>) {
-        self.async_methods.push((name, callback));
-    }
-
-    fn add_meta_callback(&mut self, name: String, callback: Callback<'lua, 'static>) {
-        self.meta_methods.push((name, callback));
-    }
-
-    #[cfg(feature = "async")]
-    fn add_async_meta_callback(&mut self, meta: String, callback: AsyncCallback<'lua, 'static>) {
-        self.async_meta_methods.push((meta, callback))
+    fn append_methods_from<S>(&mut self, other: UserDataRegistrar<'lua, S>) {
+        self.methods.extend(other.methods);
+        #[cfg(feature = "async")]
+        self.async_methods.extend(other.async_methods);
+        self.meta_methods.extend(other.meta_methods);
+        #[cfg(feature = "async")]
+        self.async_meta_methods.extend(other.async_meta_methods);
     }
 }
 
@@ -628,31 +647,13 @@ macro_rules! lua_userdata_impl {
             fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
                 let mut orig_fields = UserDataRegistrar::new();
                 T::add_fields(&mut orig_fields);
-                for (name, callback) in orig_fields.field_getters {
-                    fields.add_field_getter(name, callback);
-                }
-                for (name, callback) in orig_fields.field_setters {
-                    fields.add_field_setter(name, callback);
-                }
+                fields.append_fields_from(orig_fields);
             }
 
             fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
                 let mut orig_methods = UserDataRegistrar::new();
                 T::add_methods(&mut orig_methods);
-                for (name, callback) in orig_methods.methods {
-                    methods.add_callback(name, callback);
-                }
-                #[cfg(feature = "async")]
-                for (name, callback) in orig_methods.async_methods {
-                    methods.add_async_callback(name, callback);
-                }
-                for (meta, callback) in orig_methods.meta_methods {
-                    methods.add_meta_callback(meta, callback);
-                }
-                #[cfg(feature = "async")]
-                for (meta, callback) in orig_methods.async_meta_methods {
-                    methods.add_async_meta_callback(meta, callback);
-                }
+                methods.append_methods_from(orig_methods);
             }
         }
     };

src/util/mod.rs

@@ -11,9 +11,10 @@ use once_cell::sync::Lazy;
 use rustc_hash::FxHashMap;
 
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::memory::MemoryState;
 
+pub(crate) use short_names::short_type_name;
+
 static METATABLE_CACHE: Lazy<FxHashMap<TypeId, u8>> = Lazy::new(|| {
     let mut map = FxHashMap::with_capacity_and_hasher(32, Default::default());
     crate::lua::init_metatable_cache(&mut map);
@@ -401,9 +402,12 @@ unsafe extern "C" fn lua_error_impl(state: *mut ffi::lua_State) -> c_int {
 }
 
 unsafe extern "C" fn lua_isfunction_impl(state: *mut ffi::lua_State) -> c_int {
-    let t = ffi::lua_type(state, -1);
-    ffi::lua_pop(state, 1);
-    ffi::lua_pushboolean(state, (t == ffi::LUA_TFUNCTION) as c_int);
+    ffi::lua_pushboolean(state, ffi::lua_isfunction(state, -1));
+    1
+}
+
+unsafe extern "C" fn lua_istable_impl(state: *mut ffi::lua_State) -> c_int {
+    ffi::lua_pushboolean(state, ffi::lua_istable(state, -1));
     1
 }
 
@@ -417,14 +421,19 @@ unsafe fn init_userdata_metatable_index(state: *mut ffi::lua_State) -> Result<()
     // Create and cache `__index` generator
     let code = cstr!(
         r#"
-            local error, isfunction = ...
+            local error, isfunction, istable = ...
             return function (__index, field_getters, methods)
-                -- Fastpath to return methods table for index access
-                if __index == nil and field_getters == nil then
-                    return methods
+                -- Common case: has field getters and index is a table
+                if field_getters ~= nil and methods == nil and istable(__index) then
+                    return function (self, key)
+                        local field_getter = field_getters[key]
+                        if field_getter ~= nil then
+                            return field_getter(self)
+                        end
+                        return __index[key]
+                    end
                 end
 
-                -- Alternatively return a function for index access
                 return function (self, key)
                     if field_getters ~= nil then
                         local field_getter = field_getters[key]
@@ -459,7 +468,13 @@ unsafe fn init_userdata_metatable_index(state: *mut ffi::lua_State) -> Result<()
         }
         ffi::lua_pushcfunction(state, lua_error_impl);
         ffi::lua_pushcfunction(state, lua_isfunction_impl);
-        ffi::lua_call(state, 2, 1);
+        ffi::lua_pushcfunction(state, lua_istable_impl);
+        ffi::lua_call(state, 3, 1);
+
+        #[cfg(feature = "luau-jit")]
+        if ffi::luau_codegen_supported() != 0 {
+            ffi::luau_codegen_compile(state, -1);
+        }
 
         // Store in the registry
         ffi::lua_pushvalue(state, -1);
@@ -509,6 +524,11 @@ pub unsafe fn init_userdata_metatable_newindex(state: *mut ffi::lua_State) -> Re
         ffi::lua_pushcfunction(state, lua_isfunction_impl);
         ffi::lua_call(state, 2, 1);
 
+        #[cfg(feature = "luau-jit")]
+        if ffi::luau_codegen_supported() != 0 {
+            ffi::luau_codegen_compile(state, -1);
+        }
+
         // Store in the registry
         ffi::lua_pushvalue(state, -1);
         ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, newindex_key);
@@ -1057,3 +1077,5 @@ static DESTRUCTED_USERDATA_METATABLE: u8 = 0;
 static ERROR_PRINT_BUFFER_KEY: u8 = 0;
 static USERDATA_METATABLE_INDEX: u8 = 0;
 static USERDATA_METATABLE_NEWINDEX: u8 = 0;
+
+mod short_names;

src/util/short_names.rs

@@ -0,0 +1,84 @@
+//! Mostly copied from bevy_utils
+//! https://github.com/bevyengine/bevy/blob/main/crates/bevy_utils/src/short_names.rs
+
+use std::any::type_name;
+
+/// Returns a short version of a type name `T` without all module paths.
+///
+/// The short name of a type is its full name as returned by
+/// [`std::any::type_name`], but with the prefix of all paths removed. For
+/// example, the short name of `alloc::vec::Vec<core::option::Option<u32>>`
+/// would be `Vec<Option<u32>>`.
+pub(crate) fn short_type_name<T: ?Sized>() -> String {
+    let full_name = type_name::<T>();
+
+    // Generics result in nested paths within <..> blocks.
+    // Consider "core::option::Option<alloc::string::String>".
+    // To tackle this, we parse the string from left to right, collapsing as we go.
+    let mut index: usize = 0;
+    let end_of_string = full_name.len();
+    let mut parsed_name = String::new();
+
+    while index < end_of_string {
+        let rest_of_string = full_name.get(index..end_of_string).unwrap_or_default();
+
+        // Collapse everything up to the next special character,
+        // then skip over it
+        if let Some(special_character_index) = rest_of_string
+            .find(|c: char| [' ', '<', '>', '(', ')', '[', ']', ',', ';'].contains(&c))
+        {
+            let segment_to_collapse = rest_of_string
+                .get(0..special_character_index)
+                .unwrap_or_default();
+            parsed_name += collapse_type_name(segment_to_collapse);
+            // Insert the special character
+            let special_character =
+                &rest_of_string[special_character_index..=special_character_index];
+            parsed_name.push_str(special_character);
+
+            match special_character {
+                ">" | ")" | "]"
+                    if rest_of_string[special_character_index + 1..].starts_with("::") =>
+                {
+                    parsed_name.push_str("::");
+                    // Move the index past the "::"
+                    index += special_character_index + 3;
+                }
+                // Move the index just past the special character
+                _ => index += special_character_index + 1,
+            }
+        } else {
+            // If there are no special characters left, we're done!
+            parsed_name += collapse_type_name(rest_of_string);
+            index = end_of_string;
+        }
+    }
+    parsed_name
+}
+
+#[inline(always)]
+fn collapse_type_name(string: &str) -> &str {
+    string.rsplit("::").next().unwrap()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::short_type_name;
+    use std::collections::HashMap;
+
+    #[test]
+    fn tests() {
+        assert_eq!(short_type_name::<String>(), "String");
+        assert_eq!(short_type_name::<Option<String>>(), "Option<String>");
+        assert_eq!(short_type_name::<(String, &str)>(), "(String, &str)");
+        assert_eq!(short_type_name::<[i32; 3]>(), "[i32; 3]");
+        assert_eq!(
+            short_type_name::<HashMap<String, Option<[i32; 3]>>>(),
+            "HashMap<String, Option<[i32; 3]>>"
+        );
+        assert_eq!(
+            short_type_name::<dyn Fn(i32) -> i32>(),
+            "dyn Fn(i32) -> i32"
+        );
+    }
+}

src/value.rs

@@ -1,8 +1,11 @@
+use std::cmp::Ordering;
+use std::collections::HashSet;
 use std::iter::{self, FromIterator};
 use std::ops::Index;
 use std::os::raw::c_void;
+use std::string::String as StdString;
 use std::sync::Arc;
-use std::{ptr, slice, str, vec};
+use std::{fmt, ptr, slice, str, vec};
 
 #[cfg(feature = "serialize")]
 use {
@@ -12,7 +15,6 @@ use {
 };
 
 use crate::error::{Error, Result};
-use crate::ffi;
 use crate::function::Function;
 use crate::lua::Lua;
 use crate::string::String;
@@ -20,11 +22,12 @@ use crate::table::Table;
 use crate::thread::Thread;
 use crate::types::{Integer, LightUserData, Number};
 use crate::userdata::AnyUserData;
+use crate::util::{check_stack, StackGuard};
 
 /// A dynamically typed Lua value. The `String`, `Table`, `Function`, `Thread`, and `UserData`
 /// variants contain handle types into the internal Lua state. It is a logic error to mix handle
 /// types between separate `Lua` instances, and doing so will result in a panic.
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub enum Value<'lua> {
     /// The Lua value `nil`.
     Nil,
@@ -62,6 +65,12 @@ pub enum Value<'lua> {
 pub use self::Value::Nil;
 
 impl<'lua> Value<'lua> {
+    /// A special value (lightuserdata) to represent null value.
+    ///
+    /// It can be used in Lua tables without downsides of `nil`.
+    pub const NULL: Value<'static> = Value::LightUserData(LightUserData(ptr::null_mut()));
+
+    /// Returns type name of this value.
     pub const fn type_name(&self) -> &'static str {
         match *self {
             Value::Nil => "nil",
@@ -121,6 +130,134 @@ impl<'lua> Value<'lua> {
             }
         }
     }
+
+    /// Converts the value to a string.
+    ///
+    /// If the value has a metatable with a `__tostring` method, then it will be called to get the result.
+    pub fn to_string(&self) -> Result<StdString> {
+        match self {
+            Value::Nil => Ok("nil".to_string()),
+            Value::Boolean(b) => Ok(b.to_string()),
+            Value::LightUserData(ud) if ud.0.is_null() => Ok("null".to_string()),
+            Value::LightUserData(ud) => Ok(format!("lightuserdata: {:p}", ud.0)),
+            Value::Integer(i) => Ok(i.to_string()),
+            Value::Number(n) => Ok(n.to_string()),
+            #[cfg(feature = "luau")]
+            Value::Vector(x, y, z) => Ok(format!("vector({x}, {y}, {z})")),
+            Value::String(s) => Ok(s.to_str()?.to_string()),
+            Value::Table(Table(r))
+            | Value::Function(Function(r))
+            | Value::Thread(Thread(r))
+            | Value::UserData(AnyUserData(r)) => unsafe {
+                let state = r.lua.state();
+                let _guard = StackGuard::new(state);
+                check_stack(state, 3)?;
+
+                r.lua.push_ref(r);
+                protect_lua!(state, 1, 1, fn(state) {
+                    ffi::luaL_tolstring(state, -1, ptr::null_mut());
+                })?;
+                Ok(String(r.lua.pop_ref()).to_str()?.to_string())
+            },
+            Value::Error(err) => Ok(err.to_string()),
+        }
+    }
+
+    // Compares two values.
+    // Used to sort values for Debug printing.
+    pub(crate) fn cmp(&self, other: &Self) -> Ordering {
+        fn cmp_num(a: Number, b: Number) -> Ordering {
+            match (a, b) {
+                _ if a < b => Ordering::Less,
+                _ if a > b => Ordering::Greater,
+                _ => Ordering::Equal,
+            }
+        }
+
+        match (self, other) {
+            // Nil
+            (Value::Nil, Value::Nil) => Ordering::Equal,
+            (Value::Nil, _) => Ordering::Less,
+            (_, Value::Nil) => Ordering::Greater,
+            // Null (a special case)
+            (Value::LightUserData(ud1), Value::LightUserData(ud2)) if ud1 == ud2 => Ordering::Equal,
+            (Value::LightUserData(ud1), _) if ud1.0.is_null() => Ordering::Less,
+            (_, Value::LightUserData(ud2)) if ud2.0.is_null() => Ordering::Greater,
+            // Boolean
+            (Value::Boolean(a), Value::Boolean(b)) => a.cmp(b),
+            (Value::Boolean(_), _) => Ordering::Less,
+            (_, Value::Boolean(_)) => Ordering::Greater,
+            // Integer && Number
+            (Value::Integer(a), Value::Integer(b)) => a.cmp(b),
+            (&Value::Integer(a), &Value::Number(b)) => cmp_num(a as Number, b),
+            (&Value::Number(a), &Value::Integer(b)) => cmp_num(a, b as Number),
+            (&Value::Number(a), &Value::Number(b)) => cmp_num(a, b),
+            (Value::Integer(_) | Value::Number(_), _) => Ordering::Less,
+            (_, Value::Integer(_) | Value::Number(_)) => Ordering::Greater,
+            // String
+            (Value::String(a), Value::String(b)) => a.as_bytes().cmp(b.as_bytes()),
+            (Value::String(_), _) => Ordering::Less,
+            (_, Value::String(_)) => Ordering::Greater,
+            // Other variants can be randomly ordered
+            (a, b) => a.to_pointer().cmp(&b.to_pointer()),
+        }
+    }
+
+    pub(crate) fn fmt_pretty(
+        &self,
+        fmt: &mut fmt::Formatter,
+        recursive: bool,
+        ident: usize,
+        visited: &mut HashSet<*const c_void>,
+    ) -> fmt::Result {
+        match self {
+            Value::Nil => write!(fmt, "nil"),
+            Value::Boolean(b) => write!(fmt, "{b}"),
+            Value::LightUserData(ud) if ud.0.is_null() => write!(fmt, "null"),
+            Value::LightUserData(ud) => write!(fmt, "lightuserdata: {:?}", ud.0),
+            Value::Integer(i) => write!(fmt, "{i}"),
+            Value::Number(n) => write!(fmt, "{n}"),
+            #[cfg(feature = "luau")]
+            Value::Vector(x, y, z) => write!(fmt, "vector({x}, {y}, {z})"),
+            Value::String(s) => write!(fmt, "{s:?}"),
+            Value::Table(t) if recursive && !visited.contains(&t.to_pointer()) => {
+                t.fmt_pretty(fmt, ident, visited)
+            }
+            t @ Value::Table(_) => write!(fmt, "table: {:?}", t.to_pointer()),
+            f @ Value::Function(_) => write!(fmt, "function: {:?}", f.to_pointer()),
+            t @ Value::Thread(_) => write!(fmt, "thread: {:?}", t.to_pointer()),
+            u @ Value::UserData(ud) => {
+                let name = ud.type_name().ok().flatten();
+                let name = name.unwrap_or_else(|| "userdata".to_string());
+                write!(fmt, "{name}: {:?}", u.to_pointer())
+            }
+            Value::Error(e) if recursive => write!(fmt, "{e:?}"),
+            Value::Error(_) => write!(fmt, "error"),
+        }
+    }
+}
+
+impl fmt::Debug for Value<'_> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        if fmt.alternate() {
+            return self.fmt_pretty(fmt, true, 0, &mut HashSet::new());
+        }
+        match self {
+            Value::Nil => write!(fmt, "Nil"),
+            Value::Boolean(b) => write!(fmt, "Boolean({b})"),
+            Value::LightUserData(ud) => write!(fmt, "{ud:?}"),
+            Value::Integer(i) => write!(fmt, "Integer({i})"),
+            Value::Number(n) => write!(fmt, "Number({n})"),
+            #[cfg(feature = "luau")]
+            Value::Vector(x, y, z) => write!(fmt, "Vector({x}, {y}, {z})"),
+            Value::String(s) => write!(fmt, "String({s:?})"),
+            Value::Table(t) => write!(fmt, "{t:?}"),
+            Value::Function(f) => write!(fmt, "{f:?}"),
+            Value::Thread(t) => write!(fmt, "{t:?}"),
+            Value::UserData(ud) => write!(fmt, "{ud:?}"),
+            Value::Error(e) => write!(fmt, "Error({e:?})"),
+        }
+    }
 }
 
 impl<'lua> PartialEq for Value<'lua> {

tarpaulin.toml

@@ -0,0 +1,8 @@
+[lua54_coverage]
+features = "lua54,vendored,async,serialize,macros,unstable"
+
+[lua51_coverage]
+features = "lua51,vendored,async,serialize,macros,unstable"
+
+[luau_coverage]
+features = "luau,async,serialize,macros,unstable"

tests/async.rs

@@ -1,7 +1,7 @@
 #![cfg(feature = "async")]
 
 use std::sync::atomic::{AtomicU64, Ordering};
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
 use futures_timer::Delay;
@@ -9,7 +9,7 @@ use futures_util::stream::TryStreamExt;
 
 use mlua::{
     AnyUserDataExt, Error, Function, Lua, LuaOptions, Result, StdLib, Table, TableExt, UserData,
-    UserDataMethods,
+    UserDataMethods, Value,
 };
 
 #[tokio::test]
@@ -26,7 +26,6 @@ async fn test_async_function() -> Result<()> {
     Ok(())
 }
 
-#[cfg(feature = "unstable")]
 #[tokio::test]
 async fn test_async_function_wrap() -> Result<()> {
     let lua = Lua::new();
@@ -271,6 +270,24 @@ async fn test_async_thread() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_async_thread_capture() -> Result<()> {
+    let lua = Lua::new();
+
+    let f = lua.create_async_function(move |_lua, v: Value| async move {
+        tokio::task::yield_now().await;
+        drop(v);
+        Ok(())
+    })?;
+
+    let thread = lua.create_thread(f)?;
+    // After first resume, `v: Value` is captured in the coroutine
+    thread.resume::<_, ()>("abc").unwrap();
+    drop(thread);
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn test_async_table() -> Result<()> {
     let options = LuaOptions::new().thread_pool_size(4);
@@ -467,3 +484,43 @@ async fn test_async_thread_error() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(all(feature = "unstable", not(feature = "send")))]
+#[tokio::test]
+async fn test_owned_async_call() -> Result<()> {
+    let lua = Lua::new();
+
+    let hello = lua
+        .create_async_function(|_, name: String| async move {
+            Delay::new(Duration::from_millis(10)).await;
+            Ok(format!("hello, {}!", name))
+        })?
+        .into_owned();
+    drop(lua);
+
+    assert_eq!(hello.call_async::<_, String>("alex").await?, "hello, alex!");
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn test_async_terminate() -> Result<()> {
+    let lua = Lua::new();
+
+    let mutex = Arc::new(Mutex::new(0u32));
+    let mutex2 = mutex.clone();
+    let func = lua.create_async_function(move |_, ()| {
+        let mutex = mutex2.clone();
+        async move {
+            let _guard = mutex.lock();
+            Delay::new(Duration::from_millis(100)).await;
+            Ok(())
+        }
+    })?;
+
+    let _ = tokio::time::timeout(Duration::from_millis(30), func.call_async::<_, ()>(())).await;
+    lua.gc_collect()?;
+    assert!(mutex.try_lock().is_ok());
+
+    Ok(())
+}

tests/compile/lua_norefunwindsafe.stderr

@@ -1,22 +1,28 @@
-error[E0277]: the type `UnsafeCell<mlua::lua::LuaInner>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> tests/compile/lua_norefunwindsafe.rs:7:5
-    |
-7   |     catch_unwind(|| lua.create_table().unwrap());
-    |     ^^^^^^^^^^^^ `UnsafeCell<mlua::lua::LuaInner>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::lua::LuaInner>`
-    = note: required because it appears within the type `alloc::sync::ArcInner<UnsafeCell<mlua::lua::LuaInner>>`
-    = note: required because it appears within the type `PhantomData<alloc::sync::ArcInner<UnsafeCell<mlua::lua::LuaInner>>>`
-    = note: required because it appears within the type `Arc<UnsafeCell<mlua::lua::LuaInner>>`
-    = note: required because it appears within the type `Lua`
-    = note: required because of the requirements on the impl of `UnwindSafe` for `&Lua`
+error[E0277]: the type `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+ --> tests/compile/lua_norefunwindsafe.rs:7:18
+  |
+7 |     catch_unwind(|| lua.create_table().unwrap());
+  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+  |     |
+  |     required by a bound introduced by this call
+  |
+  = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::lua::ExtraData>`
+  = note: required because it appears within the type `ArcInner<UnsafeCell<ExtraData>>`
+  = note: required because it appears within the type `PhantomData<ArcInner<UnsafeCell<ExtraData>>>`
+  = note: required because it appears within the type `Arc<UnsafeCell<ExtraData>>`
+  = note: required because it appears within the type `LuaInner`
+  = note: required because it appears within the type `ArcInner<LuaInner>`
+  = note: required because it appears within the type `PhantomData<ArcInner<LuaInner>>`
+  = note: required because it appears within the type `Arc<LuaInner>`
+  = note: required because it appears within the type `Lua`
+  = note: required for `&Lua` to implement `UnwindSafe`
 note: required because it's used within this closure
-   --> tests/compile/lua_norefunwindsafe.rs:7:18
-    |
-7   |     catch_unwind(|| lua.create_table().unwrap());
-    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/lua_norefunwindsafe.rs:7:18
+  |
+7 |     catch_unwind(|| lua.create_table().unwrap());
+  |                  ^^
 note: required by a bound in `catch_unwind`
-   --> $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`
+ --> $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`

tests/compile/non_send.stderr

@@ -1,26 +1,25 @@
 error[E0277]: `Rc<Cell<i32>>` cannot be sent between threads safely
-    --> tests/compile/non_send.rs:11:9
-     |
-11   |       lua.create_function(move |_, ()| {
-     |  _________^^^^^^^^^^^^^^^_-
-     | |         |
-     | |         `Rc<Cell<i32>>` cannot be sent between threads safely
-12   | |         Ok(data.get())
-13   | |     })?
-     | |_____- within this `[closure@$DIR/tests/compile/non_send.rs:11:25: 13:6]`
-     |
-     = help: within `[closure@$DIR/tests/compile/non_send.rs:11:25: 13:6]`, the trait `Send` is not implemented for `Rc<Cell<i32>>`
+  --> tests/compile/non_send.rs:11:25
+   |
+11 |       lua.create_function(move |_, ()| {
+   |           --------------- ^-----------
+   |           |               |
+   |  _________|_______________within this `[closure@$DIR/tests/compile/non_send.rs:11:25: 11:37]`
+   | |         |
+   | |         required by a bound introduced by this call
+12 | |         Ok(data.get())
+13 | |     })?
+   | |_____^ `Rc<Cell<i32>>` cannot be sent between threads safely
+   |
+   = help: within `[closure@$DIR/tests/compile/non_send.rs:11:25: 11:37]`, the trait `Send` is not implemented for `Rc<Cell<i32>>`
 note: required because it's used within this closure
-    --> tests/compile/non_send.rs:11:25
-     |
-11   |       lua.create_function(move |_, ()| {
-     |  _________________________^
-12   | |         Ok(data.get())
-13   | |     })?
-     | |_____^
-     = note: required because of the requirements on the impl of `mlua::types::MaybeSend` for `[closure@$DIR/tests/compile/non_send.rs:11:25: 13:6]`
+  --> tests/compile/non_send.rs:11:25
+   |
+11 |     lua.create_function(move |_, ()| {
+   |                         ^^^^^^^^^^^^
+   = note: required for `[closure@$DIR/tests/compile/non_send.rs:11:25: 11:37]` to implement `mlua::types::MaybeSend`
 note: required by a bound in `Lua::create_function`
-    --> src/lua.rs
-     |
-     |         F: 'static + MaybeSend + Fn(&'lua Lua, A) -> Result<R>,
-     |                      ^^^^^^^^^ required by this bound in `Lua::create_function`
+  --> src/lua.rs
+   |
+   |         F: 'static + MaybeSend + Fn(&'lua Lua, A) -> Result<R>,
+   |                      ^^^^^^^^^ required by this bound in `Lua::create_function`

tests/compile/ref_nounwindsafe.stderr

@@ -1,24 +1,30 @@
-error[E0277]: the type `UnsafeCell<mlua::lua::LuaInner>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-   --> tests/compile/ref_nounwindsafe.rs:8:5
-    |
-8   |     catch_unwind(move || table.set("a", "b").unwrap());
-    |     ^^^^^^^^^^^^ `UnsafeCell<mlua::lua::LuaInner>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
-    |
-    = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::lua::LuaInner>`
-    = note: required because it appears within the type `alloc::sync::ArcInner<UnsafeCell<mlua::lua::LuaInner>>`
-    = note: required because it appears within the type `PhantomData<alloc::sync::ArcInner<UnsafeCell<mlua::lua::LuaInner>>>`
-    = note: required because it appears within the type `Arc<UnsafeCell<mlua::lua::LuaInner>>`
-    = note: required because it appears within the type `Lua`
-    = note: required because of the requirements on the impl of `UnwindSafe` for `&Lua`
-    = note: required because it appears within the type `mlua::types::LuaRef<'_>`
-    = note: required because it appears within the type `LuaTable<'_>`
+error[E0277]: the type `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+ --> tests/compile/ref_nounwindsafe.rs:8:18
+  |
+8 |     catch_unwind(move || table.set("a", "b").unwrap());
+  |     ------------ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<mlua::lua::ExtraData>` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
+  |     |
+  |     required by a bound introduced by this call
+  |
+  = help: within `Lua`, the trait `RefUnwindSafe` is not implemented for `UnsafeCell<mlua::lua::ExtraData>`
+  = note: required because it appears within the type `ArcInner<UnsafeCell<ExtraData>>`
+  = note: required because it appears within the type `PhantomData<ArcInner<UnsafeCell<ExtraData>>>`
+  = note: required because it appears within the type `Arc<UnsafeCell<ExtraData>>`
+  = note: required because it appears within the type `LuaInner`
+  = note: required because it appears within the type `ArcInner<LuaInner>`
+  = note: required because it appears within the type `PhantomData<ArcInner<LuaInner>>`
+  = note: required because it appears within the type `Arc<LuaInner>`
+  = note: required because it appears within the type `Lua`
+  = note: required for `&Lua` to implement `UnwindSafe`
+  = note: required because it appears within the type `LuaRef<'_>`
+  = note: required because it appears within the type `Table<'_>`
 note: required because it's used within this closure
-   --> tests/compile/ref_nounwindsafe.rs:8:18
-    |
-8   |     catch_unwind(move || table.set("a", "b").unwrap());
-    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/ref_nounwindsafe.rs:8:18
+  |
+8 |     catch_unwind(move || table.set("a", "b").unwrap());
+  |                  ^^^^^^^
 note: required by a bound in `catch_unwind`
-   --> $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`
+ --> $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`

tests/compile/static_callback_args.stderr

@@ -1,15 +1,17 @@
 error[E0597]: `lua` does not live long enough
   --> tests/compile/static_callback_args.rs:12:5
    |
-12 |  /     lua.create_function(|_, table: Table| {
-13 |  |         BAD_TIME.with(|bt| {
-   |  |_________-
+10 |        let lua = Lua::new();
+   |            --- binding `lua` declared here
+11 |
+12 | /      lua.create_function(|_, table: Table| {
+13 | |/         BAD_TIME.with(|bt| {
 14 | ||             *bt.borrow_mut() = Some(table);
 15 | ||         });
    | ||__________- argument requires that `lua` is borrowed for `'static`
-16 |  |         Ok(())
-17 |  |     })?
-   |  |______^ borrowed value does not live long enough
+16 | |          Ok(())
+17 | |      })?
+   | |_______^ borrowed value does not live long enough
 ...
 32 |    }
    |    - `lua` dropped here while still borrowed
@@ -17,15 +19,17 @@ error[E0597]: `lua` does not live long enough
 error[E0505]: cannot move out of `lua` because it is borrowed
   --> tests/compile/static_callback_args.rs:22:10
    |
-12 |  /     lua.create_function(|_, table: Table| {
-13 |  |         BAD_TIME.with(|bt| {
-   |  |_________-
+10 |        let lua = Lua::new();
+   |            --- binding `lua` declared here
+11 |
+12 | /      lua.create_function(|_, table: Table| {
+13 | |/         BAD_TIME.with(|bt| {
 14 | ||             *bt.borrow_mut() = Some(table);
 15 | ||         });
    | ||__________- argument requires that `lua` is borrowed for `'static`
-16 |  |         Ok(())
-17 |  |     })?
-   |  |______- borrow of `lua` occurs here
+16 | |          Ok(())
+17 | |      })?
+   | |_______- borrow of `lua` occurs here
 ...
 22 |        drop(lua);
    |             ^^^ move out of `lua` occurs here

tests/debug.rs

@@ -0,0 +1,15 @@
+use mlua::{Lua, Result};
+
+#[test]
+fn test_debug_format() -> Result<()> {
+    let lua = Lua::new();
+
+    // Globals
+    let globals = lua.globals();
+    let dump = format!("{globals:#?}");
+    assert!(dump.starts_with("{\n  [\"_G\"] = table:"));
+
+    // TODO: Other cases
+
+    Ok(())
+}

tests/error.rs

@@ -1,3 +1,5 @@
+use std::io;
+
 use mlua::{Error, ErrorContext, Lua, Result};
 
 #[test]
@@ -29,5 +31,20 @@ fn test_error_context() -> Result<()> {
     println!("{msg2}");
     assert!(msg2.contains("error converting Lua nil to String"));
 
+    // Rewrite context message and test `downcast_ref`
+    let func3 = lua.create_function(|_, ()| {
+        Err::<(), _>(Error::external(io::Error::new(
+            io::ErrorKind::Other,
+            "other",
+        )))
+        .context("some context")
+        .context("some new context")
+    })?;
+    let res = func3.call::<_, ()>(()).err().unwrap();
+    let Error::CallbackError { cause, .. } = &res else { unreachable!() };
+    assert!(!res.to_string().contains("some context"));
+    assert!(res.to_string().contains("some new context"));
+    assert!(cause.downcast_ref::<io::Error>().is_some());
+
     Ok(())
 }

tests/function.rs

@@ -1,4 +1,4 @@
-use mlua::{Function, Lua, Result, String};
+use mlua::{Function, Lua, Result, String, Table};
 
 #[test]
 fn test_function() -> Result<()> {
@@ -114,6 +114,66 @@ fn test_dump() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_function_environment() -> Result<()> {
+    let lua = Lua::new();
+
+    // We must not get or set environment for C functions
+    let rust_func = lua.create_function(|_, ()| Ok("hello"))?;
+    assert_eq!(rust_func.environment(), None);
+    assert_eq!(rust_func.set_environment(lua.globals()).ok(), Some(false));
+
+    // Test getting Lua function environment
+    lua.globals().set("hello", "global")?;
+    let lua_func = lua
+        .load(
+            r#"
+        local t = ""
+        return function()
+            -- two upvalues
+            return t .. hello
+        end
+    "#,
+        )
+        .eval::<Function>()?;
+    let lua_func2 = lua.load("return hello").into_function()?;
+    assert_eq!(lua_func.call::<_, String>(())?, "global");
+    assert_eq!(lua_func.environment(), Some(lua.globals()));
+
+    // Test changing the environment
+    let env = lua.create_table_from([("hello", "local")])?;
+    assert!(lua_func.set_environment(env.clone())?);
+    assert_eq!(lua_func.call::<_, String>(())?, "local");
+    assert_eq!(lua_func2.call::<_, String>(())?, "global");
+
+    // More complex case
+    lua.load(
+        r#"
+        local number = 15
+        function lucky() return tostring("number is "..number) end
+        new_env = {
+            tostring = function() return tostring(number) end,
+        }
+    "#,
+    )
+    .exec()?;
+    let lucky = lua.globals().get::<_, Function>("lucky")?;
+    assert_eq!(lucky.call::<_, String>(())?, "number is 15");
+    let new_env = lua.globals().get::<_, Table>("new_env")?;
+    lucky.set_environment(new_env)?;
+    assert_eq!(lucky.call::<_, String>(())?, "15");
+
+    // Test inheritance
+    let lua_func2 = lua
+        .load(r#"return function() return (function() return hello end)() end"#)
+        .eval::<Function>()?;
+    assert!(lua_func2.set_environment(env.clone())?);
+    lua.gc_collect()?;
+    assert_eq!(lua_func2.call::<_, String>(())?, "local");
+
+    Ok(())
+}
+
 #[test]
 fn test_function_info() -> Result<()> {
     let lua = Lua::new();
@@ -135,40 +195,42 @@ fn test_function_info() -> Result<()> {
 
     let function1_info = function1.info();
     #[cfg(feature = "luau")]
-    assert_eq!(function1_info.name, Some(b"function1".to_vec()));
-    assert_eq!(function1_info.source, Some(b"source1".to_vec()));
+    assert_eq!(function1_info.name.as_deref(), Some("function1"));
+    assert_eq!(function1_info.source.as_deref(), Some(b"source1".as_ref()));
     assert_eq!(function1_info.line_defined, 2);
     #[cfg(not(feature = "luau"))]
     assert_eq!(function1_info.last_line_defined, 4);
-    assert_eq!(function1_info.what, Some(b"Lua".to_vec()));
+    #[cfg(feature = "luau")]
+    assert_eq!(function1_info.last_line_defined, -1);
+    assert_eq!(function1_info.what.as_deref(), Some("Lua"));
 
     let function2_info = function2.info();
     assert_eq!(function2_info.name, None);
-    assert_eq!(function2_info.source, Some(b"source1".to_vec()));
+    assert_eq!(function2_info.source.as_deref(), Some(b"source1".as_ref()));
     assert_eq!(function2_info.line_defined, 3);
     #[cfg(not(feature = "luau"))]
     assert_eq!(function2_info.last_line_defined, 3);
-    assert_eq!(function2_info.what, Some(b"Lua".to_vec()));
+    #[cfg(feature = "luau")]
+    assert_eq!(function2_info.last_line_defined, -1);
+    assert_eq!(function2_info.what.as_deref(), Some("Lua"));
 
     let function3_info = function3.info();
     assert_eq!(function3_info.name, None);
-    assert_eq!(function3_info.source, Some(b"=[C]".to_vec()));
+    assert_eq!(function3_info.source.as_deref(), Some(b"=[C]".as_ref()));
     assert_eq!(function3_info.line_defined, -1);
-    #[cfg(not(feature = "luau"))]
     assert_eq!(function3_info.last_line_defined, -1);
-    assert_eq!(function3_info.what, Some(b"C".to_vec()));
+    assert_eq!(function3_info.what.as_deref(), Some("C"));
 
     let print_info = globals.get::<_, Function>("print")?.info();
     #[cfg(feature = "luau")]
-    assert_eq!(print_info.name, Some(b"print".to_vec()));
-    assert_eq!(print_info.source, Some(b"=[C]".to_vec()));
-    assert_eq!(print_info.what, Some(b"C".to_vec()));
+    assert_eq!(print_info.name.as_deref(), Some("print"));
+    assert_eq!(print_info.source.as_deref(), Some(b"=[C]".as_ref()));
+    assert_eq!(print_info.what.as_deref(), Some("C"));
     assert_eq!(print_info.line_defined, -1);
 
     Ok(())
 }
 
-#[cfg(feature = "unstable")]
 #[test]
 fn test_function_wrap() -> Result<()> {
     use mlua::Error;
@@ -200,3 +262,45 @@ fn test_function_wrap() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(all(feature = "unstable", not(feature = "send")))]
+#[test]
+fn test_owned_function() -> Result<()> {
+    let lua = Lua::new();
+
+    let f = lua
+        .create_function(|_, ()| Ok("hello, world!"))?
+        .into_owned();
+    drop(lua);
+
+    // We still should be able to call the function despite Lua is dropped
+    let s = f.call::<_, String>(())?;
+    assert_eq!(s.to_string_lossy(), "hello, world!");
+
+    Ok(())
+}
+
+#[cfg(all(feature = "unstable", not(feature = "send")))]
+#[test]
+fn test_owned_function_drop() -> Result<()> {
+    let rc = std::sync::Arc::new(());
+
+    {
+        let lua = Lua::new();
+
+        lua.set_app_data(rc.clone());
+
+        let f1 = lua
+            .create_function(|_, ()| Ok("hello, world!"))?
+            .into_owned();
+        let f2 =
+            lua.create_function(move |_, ()| f1.to_ref().call::<_, std::string::String>(()))?;
+        assert_eq!(f2.call::<_, String>(())?.to_string_lossy(), "hello, world!");
+    }
+
+    // Check that Lua is properly destroyed
+    // It works because we collect garbage when Lua goes out of scope
+    assert_eq!(std::sync::Arc::strong_count(&rc), 1);
+
+    Ok(())
+}

tests/hooks.rs

@@ -9,11 +9,9 @@ use std::sync::{Arc, Mutex};
 use mlua::{DebugEvent, Error, HookTriggers, Lua, Result, Value};
 
 #[test]
-fn test_hook_triggers_bitor() {
-    let trigger = HookTriggers::on_calls()
-        | HookTriggers::on_returns()
-        | HookTriggers::every_line()
-        | HookTriggers::every_nth_instruction(5);
+fn test_hook_triggers() {
+    let trigger = HookTriggers::new().on_calls().on_returns()
+        | HookTriggers::new().every_line().every_nth_instruction(5);
 
     assert!(trigger.on_calls);
     assert!(trigger.on_returns);
@@ -27,7 +25,7 @@ fn test_line_counts() -> Result<()> {
     let hook_output = output.clone();
 
     let lua = Lua::new();
-    lua.set_hook(HookTriggers::every_line(), move |_lua, debug| {
+    lua.set_hook(HookTriggers::EVERY_LINE, move |_lua, debug| {
         assert_eq!(debug.event(), DebugEvent::Line);
         hook_output.lock().unwrap().push(debug.curr_line());
         Ok(())
@@ -59,7 +57,7 @@ fn test_function_calls() -> Result<()> {
     let hook_output = output.clone();
 
     let lua = Lua::new();
-    lua.set_hook(HookTriggers::on_calls(), move |_lua, debug| {
+    lua.set_hook(HookTriggers::ON_CALLS, move |_lua, debug| {
         assert_eq!(debug.event(), DebugEvent::Call);
         let names = debug.names();
         let source = debug.source();
@@ -104,7 +102,7 @@ fn test_function_calls() -> Result<()> {
 fn test_error_within_hook() -> Result<()> {
     let lua = Lua::new();
 
-    lua.set_hook(HookTriggers::every_line(), |_lua, _debug| {
+    lua.set_hook(HookTriggers::EVERY_LINE, |_lua, _debug| {
         Err(Error::RuntimeError(
             "Something happened in there!".to_string(),
         ))
@@ -136,7 +134,7 @@ fn test_limit_execution_instructions() -> Result<()> {
 
     let max_instructions = AtomicI64::new(10000);
     lua.set_hook(
-        HookTriggers::every_nth_instruction(30),
+        HookTriggers::new().every_nth_instruction(30),
         move |_lua, debug| {
             assert_eq!(debug.event(), DebugEvent::Count);
             if max_instructions.fetch_sub(30, Ordering::Relaxed) <= 30 {
@@ -166,11 +164,14 @@ fn test_limit_execution_instructions() -> Result<()> {
 fn test_hook_removal() -> Result<()> {
     let lua = Lua::new();
 
-    lua.set_hook(HookTriggers::every_nth_instruction(1), |_lua, _debug| {
-        Err(Error::RuntimeError(
-            "this hook should've been removed by this time".to_string(),
-        ))
-    })?;
+    lua.set_hook(
+        HookTriggers::new().every_nth_instruction(1),
+        |_lua, _debug| {
+            Err(Error::RuntimeError(
+                "this hook should've been removed by this time".to_string(),
+            ))
+        },
+    )?;
 
     assert!(lua.load("local x = 1").exec().is_err());
     lua.remove_hook();
@@ -193,11 +194,11 @@ fn test_hook_swap_within_hook() -> Result<()> {
         tl.borrow()
             .as_ref()
             .unwrap()
-            .set_hook(HookTriggers::every_line(), move |lua, _debug| {
+            .set_hook(HookTriggers::EVERY_LINE, move |lua, _debug| {
                 lua.globals().set("ok", 1i64)?;
                 TL_LUA.with(|tl| {
                     tl.borrow().as_ref().unwrap().set_hook(
-                        HookTriggers::every_line(),
+                        HookTriggers::EVERY_LINE,
                         move |lua, _debug| {
                             lua.load(
                                 r#"
@@ -233,3 +234,39 @@ fn test_hook_swap_within_hook() -> Result<()> {
         Ok(())
     })
 }
+
+#[test]
+fn test_hook_threads() -> Result<()> {
+    let lua = Lua::new();
+
+    let func = lua
+        .load(
+            r#"
+            local x = 2 + 3
+            local y = x * 63
+            local z = string.len(x..", "..y)
+        "#,
+        )
+        .into_function()?;
+    let co = lua.create_thread(func)?;
+
+    let output = Arc::new(Mutex::new(Vec::new()));
+    let hook_output = output.clone();
+    co.set_hook(HookTriggers::EVERY_LINE, move |_lua, debug| {
+        assert_eq!(debug.event(), DebugEvent::Line);
+        hook_output.lock().unwrap().push(debug.curr_line());
+        Ok(())
+    });
+
+    co.resume(())?;
+    lua.remove_hook();
+
+    let output = output.lock().unwrap();
+    if cfg!(feature = "luajit") && lua.load("jit.version_num").eval::<i64>()? >= 20100 {
+        assert_eq!(*output, vec![2, 3, 4, 0, 4]);
+    } else {
+        assert_eq!(*output, vec![2, 3, 4]);
+    }
+
+    Ok(())
+}

tests/luau.rs

@@ -9,6 +9,16 @@ use std::sync::Arc;
 
 use mlua::{Compiler, CoverageInfo, Error, Lua, Result, Table, ThreadStatus, Value, VmState};
 
+#[test]
+fn test_version() -> Result<()> {
+    let lua = Lua::new();
+    assert!(lua
+        .globals()
+        .get::<_, String>("_VERSION")?
+        .starts_with("Luau 0."));
+    Ok(())
+}
+
 #[test]
 fn test_require() -> Result<()> {
     let lua = Lua::new();

tests/serde.rs

@@ -392,31 +392,44 @@ fn test_from_value_newtype_struct() -> Result<(), Box<dyn StdError>> {
 #[test]
 fn test_from_value_enum() -> Result<(), Box<dyn StdError>> {
     let lua = Lua::new();
+    lua.globals().set("null", lua.null())?;
 
     #[derive(Deserialize, PartialEq, Debug)]
-    enum E {
+    struct UnitStruct;
+
+    #[derive(Deserialize, PartialEq, Debug)]
+    enum E<T = ()> {
         Unit,
         Integer(u32),
         Tuple(u32, u32),
         Struct { a: u32 },
+        Wrap(T),
     }
 
     let value = lua.load(r#""Unit""#).eval()?;
-    let got = lua.from_value(value)?;
+    let got: E = lua.from_value(value)?;
     assert_eq!(E::Unit, got);
 
     let value = lua.load(r#"{Integer = 1}"#).eval()?;
-    let got = lua.from_value(value)?;
+    let got: E = 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)?;
+    let got: E = 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)?;
+    let got: E = lua.from_value(value)?;
     assert_eq!(E::Struct { a: 3 }, got);
 
+    let value = lua.load(r#"{Wrap = null}"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(E::Wrap(UnitStruct), got);
+
+    let value = lua.load(r#"{Wrap = null}"#).eval()?;
+    let got = lua.from_value(value)?;
+    assert_eq!(E::Wrap(()), got);
+
     Ok(())
 }
 

tests/string.rs

@@ -98,3 +98,22 @@ fn test_string_debug() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(all(feature = "unstable", not(feature = "send")))]
+#[test]
+fn test_owned_string() -> Result<()> {
+    let lua = Lua::new();
+
+    let s = lua.create_string("hello, world!")?.into_owned();
+    drop(lua);
+
+    // Shortcuts
+    assert_eq!(s.as_bytes(), b"hello, world!");
+    assert_eq!(s.to_str()?, "hello, world!");
+    assert_eq!(format!("{s:?}"), "\"hello, world!\"");
+
+    // Access via reference
+    assert_eq!(s.to_ref().to_string_lossy(), "hello, world!");
+
+    Ok(())
+}

tests/table.rs

@@ -392,3 +392,17 @@ fn test_table_call() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(all(feature = "unstable", not(feature = "send")))]
+#[test]
+fn test_owned_table() -> Result<()> {
+    let lua = Lua::new();
+
+    let table = lua.create_table()?.into_owned();
+    drop(lua);
+
+    table.to_ref().set("abc", 123)?;
+    assert_eq!(table.to_ref().get::<_, i64>("abc")?, 123);
+
+    Ok(())
+}

tests/tests.rs

@@ -887,19 +887,47 @@ fn test_application_data() -> Result<()> {
     lua.set_app_data("test1");
     lua.set_app_data(vec!["test2"]);
 
+    // Borrow &str immutably and Vec<&str> mutably
+    let s = lua.app_data_ref::<&str>().unwrap();
+    let mut v = lua.app_data_mut::<Vec<&str>>().unwrap();
+    v.push("test3");
+
+    // Insert of new data or removal should fail now
+    assert!(lua.try_set_app_data::<i32>(123).is_err());
+    match catch_unwind(AssertUnwindSafe(|| lua.set_app_data::<i32>(123))) {
+        Ok(_) => panic!("expected panic"),
+        Err(_) => {}
+    }
+    match catch_unwind(AssertUnwindSafe(|| lua.remove_app_data::<i32>())) {
+        Ok(_) => panic!("expected panic"),
+        Err(_) => {}
+    }
+
+    // Check display and debug impls
+    assert_eq!(format!("{s}"), "test1");
+    assert_eq!(format!("{s:?}"), "\"test1\"");
+
+    // Borrowing immutably and mutably of the same type is not allowed
+    match catch_unwind(AssertUnwindSafe(|| lua.app_data_mut::<&str>().unwrap())) {
+        Ok(_) => panic!("expected panic"),
+        Err(_) => {}
+    }
+    drop((s, v));
+
+    // Test that application data is accessible from anywhere
     let f = lua.create_function(|lua, ()| {
-        {
-            let data1 = lua.app_data_ref::<&str>().unwrap();
-            assert_eq!(*data1, "test1");
-        }
-        let mut data2 = lua.app_data_mut::<Vec<&str>>().unwrap();
-        assert_eq!(*data2, vec!["test2"]);
-        data2.push("test3");
+        let mut data1 = lua.app_data_mut::<&str>().unwrap();
+        assert_eq!(*data1, "test1");
+        *data1 = "test4";
+
+        let data2 = lua.app_data_ref::<Vec<&str>>().unwrap();
+        assert_eq!(*data2, vec!["test2", "test3"]);
+
         Ok(())
     })?;
     f.call(())?;
 
-    assert_eq!(*lua.app_data_ref::<&str>().unwrap(), "test1");
+    assert_eq!(*lua.app_data_ref::<&str>().unwrap(), "test4");
     assert_eq!(
         *lua.app_data_ref::<Vec<&str>>().unwrap(),
         vec!["test2", "test3"]
@@ -991,7 +1019,7 @@ fn test_ref_stack_exhaustion() {
     match catch_unwind(AssertUnwindSafe(|| -> Result<()> {
         let lua = Lua::new();
         let mut vals = Vec::new();
-        for _ in 0..1000000 {
+        for _ in 0..10000000 {
             vals.push(lua.create_table()?);
         }
         Ok(())

tests/userdata.rs

@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::string::String as StdString;
 use std::sync::Arc;
 #[cfg(not(feature = "parking_lot"))]
@@ -486,6 +487,7 @@ fn test_fields() -> Result<()> {
 
     impl UserData for MyUserData {
         fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+            fields.add_field("static", "constant");
             fields.add_field_method_get("val", |_, data| Ok(data.0));
             fields.add_field_method_set("val", |_, data, val| {
                 data.0 = val;
@@ -497,11 +499,7 @@ fn test_fields() -> Result<()> {
             fields
                 .add_field_function_set("uval", |_, ud, s| ud.set_user_value::<Option<String>>(s));
 
-            fields.add_meta_field_with(MetaMethod::Index, |lua| {
-                let index = lua.create_table()?;
-                index.set("f", 321)?;
-                Ok(index)
-            });
+            fields.add_meta_field(MetaMethod::Index, HashMap::from([("f", 321)]));
             fields.add_meta_field_with(MetaMethod::NewIndex, |lua| {
                 lua.create_function(|lua, (_, field, val): (AnyUserData, String, Value)| {
                     lua.globals().set(field, val)?;
@@ -516,6 +514,7 @@ fn test_fields() -> Result<()> {
     globals.set("ud", MyUserData(7))?;
     lua.load(
         r#"
+        assert(ud.static == "constant")
         assert(ud.val == 7)
         ud.val = 10
         assert(ud.val == 10)
@@ -538,30 +537,22 @@ fn test_fields() -> Result<()> {
 #[test]
 fn test_metatable() -> Result<()> {
     #[derive(Copy, Clone)]
-    struct MyUserData(i64);
+    struct MyUserData;
 
     impl UserData for MyUserData {
-        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
-            fields.add_meta_field_with("__type_name", |_| Ok("MyUserData"));
-        }
-
         fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
             methods.add_function("my_type_name", |_, data: AnyUserData| {
                 let metatable = data.get_metatable()?;
-                metatable.get::<String>("__type_name")
+                metatable.get::<String>("__name")
             });
         }
     }
 
     let lua = Lua::new();
     let globals = lua.globals();
-    globals.set("ud", MyUserData(7))?;
-    lua.load(
-        r#"
-        assert(ud:my_type_name() == "MyUserData")
-    "#,
-    )
-    .exec()?;
+    globals.set("ud", MyUserData)?;
+    lua.load(r#"assert(ud:my_type_name() == "MyUserData")"#)
+        .exec()?;
 
     let ud: AnyUserData = globals.get("ud")?;
     let metatable = ud.get_metatable()?;
@@ -583,10 +574,10 @@ fn test_metatable() -> Result<()> {
         .map(|kv: Result<(_, Value)>| Ok(kv?.0))
         .collect::<Result<Vec<_>>>()?;
     methods.sort();
-    assert_eq!(methods, vec!["__index", "__type_name"]);
+    assert_eq!(methods, vec!["__index", "__name"]);
 
     #[derive(Copy, Clone)]
-    struct MyUserData2(i64);
+    struct MyUserData2;
 
     impl UserData for MyUserData2 {
         fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
@@ -594,12 +585,25 @@ fn test_metatable() -> Result<()> {
         }
     }
 
-    match lua.create_userdata(MyUserData2(1)) {
+    match lua.create_userdata(MyUserData2) {
         Ok(_) => panic!("expected MetaMethodTypeError, got no error"),
         Err(Error::MetaMethodTypeError { .. }) => {}
         Err(e) => panic!("expected MetaMethodTypeError, got {:?}", e),
     }
 
+    #[derive(Copy, Clone)]
+    struct MyUserData3;
+
+    impl UserData for MyUserData3 {
+        fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+            fields.add_meta_field_with("__name", |_| Ok("CustomName"));
+        }
+    }
+
+    let ud = lua.create_userdata(MyUserData3)?;
+    let metatable = ud.get_metatable()?;
+    assert_eq!(metatable.get::<String>("__name")?.to_str()?, "CustomName");
+
     Ok(())
 }
 
@@ -609,6 +613,7 @@ fn test_userdata_wrapped() -> Result<()> {
 
     impl UserData for MyUserData {
         fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
+            fields.add_field("static", "constant");
             fields.add_field_method_get("data", |_, this| Ok(this.0));
             fields.add_field_method_set("data", |_, this, val| {
                 this.0 = val;
@@ -626,6 +631,7 @@ fn test_userdata_wrapped() -> Result<()> {
         globals.set("rc_refcell_ud", ud1.clone())?;
         lua.load(
             r#"
+            assert(rc_refcell_ud.static == "constant")
             rc_refcell_ud.data = rc_refcell_ud.data + 1
             assert(rc_refcell_ud.data == 2)
         "#,
@@ -641,6 +647,7 @@ fn test_userdata_wrapped() -> Result<()> {
     globals.set("arc_mutex_ud", ud2.clone())?;
     lua.load(
         r#"
+        assert(arc_mutex_ud.static == "constant")
         arc_mutex_ud.data = arc_mutex_ud.data + 1
         assert(arc_mutex_ud.data == 3)
     "#,
@@ -655,6 +662,7 @@ fn test_userdata_wrapped() -> Result<()> {
     globals.set("arc_rwlock_ud", ud3.clone())?;
     lua.load(
         r#"
+        assert(arc_rwlock_ud.static == "constant")
         arc_rwlock_ud.data = arc_rwlock_ud.data + 1
         assert(arc_rwlock_ud.data == 4)
     "#,
@@ -681,7 +689,7 @@ fn test_userdata_proxy() -> Result<()> {
 
     impl UserData for MyUserData {
         fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
-            fields.add_field_function_get("static_field", |_, _| Ok(123));
+            fields.add_field("static_field", 123);
             fields.add_field_method_get("n", |_, this| Ok(this.0));
         }
 
@@ -775,10 +783,7 @@ fn test_userdata_ext() -> Result<()> {
     assert_eq!(ud.get::<_, u32>("n")?, 123);
     ud.set("n", 321)?;
     assert_eq!(ud.get::<_, u32>("n")?, 321);
-    match ud.get::<_, u32>("non-existent") {
-        Err(Error::RuntimeError(_)) => {}
-        r => panic!("expected RuntimeError, got {r:?}"),
-    }
+    assert_eq!(ud.get::<_, Option<u32>>("non-existent")?, None);
     match ud.set::<_, u32>("non-existent", 123) {
         Err(Error::RuntimeError(_)) => {}
         r => panic!("expected RuntimeError, got {r:?}"),
@@ -820,3 +825,22 @@ fn test_userdata_method_errors() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(all(feature = "unstable", not(feature = "send")))]
+#[test]
+fn test_owned_userdata() -> Result<()> {
+    let lua = Lua::new();
+
+    let ud = lua.create_any_userdata("abc")?.into_owned();
+    drop(lua);
+
+    assert_eq!(*ud.borrow::<&str>()?, "abc");
+    *ud.borrow_mut()? = "cba";
+    assert!(matches!(
+        ud.borrow::<i64>(),
+        Err(Error::UserDataTypeMismatch)
+    ));
+    assert_eq!(ud.take::<&str>()?, "cba");
+
+    Ok(())
+}

tests/value.rs

@@ -1,6 +1,9 @@
+use std::collections::HashMap;
+use std::os::raw::c_void;
 use std::ptr;
+use std::string::String as StdString;
 
-use mlua::{Lua, MultiValue, Result, Value};
+use mlua::{Error, LightUserData, Lua, MultiValue, Result, UserData, UserDataMethods, Value};
 
 #[test]
 fn test_value_eq() -> Result<()> {
@@ -28,6 +31,7 @@ fn test_value_eq() -> Result<()> {
     "#,
     )
     .exec()?;
+    globals.set("null", Value::NULL)?;
 
     let table1: Value = globals.get("table1")?;
     let table2: Value = globals.get("table2")?;
@@ -41,6 +45,7 @@ fn test_value_eq() -> Result<()> {
     let func3: Value = globals.get("func3")?;
     let thread1: Value = globals.get("thread1")?;
     let thread2: Value = globals.get("thread2")?;
+    let null: Value = globals.get("null")?;
 
     assert!(table1 != table2);
     assert!(table1.equals(&table2)?);
@@ -54,6 +59,7 @@ fn test_value_eq() -> Result<()> {
     assert!(!func1.equals(&func3)?);
     assert!(thread1 == thread2);
     assert!(thread1.equals(&thread2)?);
+    assert!(null == Value::NULL);
 
     assert!(!table1.to_pointer().is_null());
     assert!(!ptr::eq(table1.to_pointer(), table2.to_pointer()));
@@ -81,3 +87,69 @@ fn test_multi_value() {
     multi_value.clear();
     assert!(multi_value.is_empty());
 }
+
+#[test]
+fn test_value_to_string() -> Result<()> {
+    let lua = Lua::new();
+
+    assert_eq!(Value::Nil.to_string()?, "nil");
+    assert_eq!(Value::Boolean(true).to_string()?, "true");
+    assert_eq!(Value::NULL.to_string()?, "null");
+    assert_eq!(
+        Value::LightUserData(LightUserData(0x1 as *const c_void as *mut _)).to_string()?,
+        "lightuserdata: 0x1"
+    );
+    assert_eq!(Value::Integer(1).to_string()?, "1");
+    assert_eq!(Value::Number(34.59).to_string()?, "34.59");
+    #[cfg(feature = "luau")]
+    assert_eq!(
+        Value::Vector(10.0, 11.1, 12.2).to_string()?,
+        "vector(10, 11.1, 12.2)"
+    );
+    assert_eq!(
+        Value::String(lua.create_string("hello")?).to_string()?,
+        "hello"
+    );
+
+    let table: Value = lua.load("{}").eval()?;
+    assert!(table.to_string()?.starts_with("table:"));
+    let table: Value = lua
+        .load("setmetatable({}, {__tostring = function() return 'test table' end})")
+        .eval()?;
+    assert_eq!(table.to_string()?, "test table");
+
+    let func: Value = lua.load("function() end").eval()?;
+    assert!(func.to_string()?.starts_with("function:"));
+
+    let thread: Value = lua.load("coroutine.create(function() end)").eval()?;
+    assert!(thread.to_string()?.starts_with("thread:"));
+
+    lua.register_userdata_type::<StdString>(|reg| {
+        reg.add_meta_method("__tostring", |_, this, ()| Ok(this.clone()));
+    })?;
+    let ud: Value = Value::UserData(lua.create_any_userdata(String::from("string userdata"))?);
+    assert_eq!(ud.to_string()?, "string userdata");
+
+    struct MyUserData;
+    impl UserData for MyUserData {}
+    let ud: Value = Value::UserData(lua.create_userdata(MyUserData)?);
+    assert!(ud.to_string()?.starts_with("MyUserData:"));
+
+    let err = Value::Error(Error::RuntimeError("test error".to_string()));
+    assert_eq!(err.to_string()?, "runtime error: test error");
+
+    Ok(())
+}
+
+#[test]
+fn test_debug_format() -> Result<()> {
+    let lua = Lua::new();
+
+    lua.register_userdata_type::<HashMap<i32, StdString>>(|_| {})?;
+    let ud = lua
+        .create_any_userdata::<HashMap<i32, StdString>>(HashMap::new())
+        .map(Value::UserData)?;
+    assert!(format!("{ud:#?}").starts_with("HashMap<i32, String>:"));
+
+    Ok(())
+}