v0.9.9

- Store single `AtomicI32` field instead of pair i32,AtomicBool
- Make creation faster by skipping intermediate `Value` layer
Add new `RegistryKey::id()` method to return underlying identifier

CHANGELOG.md

@@ -1,3 +1,9 @@
+## v0.9.9
+
+- Minimal Luau updated to 0.629
+- Fixed bug when attempting to reset or resume already running coroutines (#416).
+- Added `RegistryKey::id()` method to get the underlying Lua registry key id.
+
 ## v0.9.8
 
 - Fixed serializing same table multiple times (#408)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua"
-version = "0.9.8" # remember to update mlua_derive
+version = "0.9.9" # remember to update mlua_derive
 authors = ["Aleksandr Orlenko <zxteam@pm.me>", "kyren <catherine@kyju.org>"]
 rust-version = "1.71"
 edition = "2021"
@@ -45,17 +45,17 @@ unstable = []
 
 [dependencies]
 mlua_derive = { version = "=0.9.3", optional = true, path = "mlua_derive" }
-bstr = { version = "1.0", features = ["std"], default_features = false }
+bstr = { version = "1.0", features = ["std"], default-features = false }
 once_cell = { version = "1.0" }
 num-traits = { version = "0.2.14" }
-rustc-hash = "1.0"
+rustc-hash = "2.0"
 futures-util = { version = "0.3", optional = true, default-features = false, features = ["std"] }
 serde = { version = "1.0", optional = true }
 erased-serde = { version = "0.4", optional = true }
 serde-value = { version = "0.7", optional = true }
 parking_lot = { version = "0.12", optional = true }
 
-ffi = { package = "mlua-sys", version = "0.6.0", path = "mlua-sys" }
+ffi = { package = "mlua-sys", version = "0.6.1", path = "mlua-sys" }
 
 [target.'cfg(unix)'.dependencies]
 libloading = { version = "0.8", optional = true }
@@ -79,6 +79,9 @@ criterion = { version = "0.5", features = ["async_tokio"] }
 rustyline = "14.0"
 tokio = { version = "1.0", features = ["full"] }
 
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(tarpaulin_include)'] }
+
 [[bench]]
 name = "benchmark"
 harness = false

README.md

@@ -133,7 +133,7 @@ Add to `Cargo.toml` :
 
 ``` toml
 [dependencies]
-mlua = { version = "0.9.8", features = ["lua54", "vendored"] }
+mlua = { version = "0.9.9", features = ["lua54", "vendored"] }
 ```
 
 `main.rs`
@@ -168,7 +168,7 @@ Add to `Cargo.toml` :
 crate-type = ["cdylib"]
 
 [dependencies]
-mlua = { version = "0.9.8", features = ["lua54", "module"] }
+mlua = { version = "0.9.9", features = ["lua54", "module"] }
 ```
 
 `lib.rs` :

benches/benchmark.rs

@@ -268,6 +268,23 @@ fn registry_value_create(c: &mut Criterion) {
     });
 }
 
+fn registry_value_get(c: &mut Criterion) {
+    let lua = Lua::new();
+    lua.gc_stop();
+
+    let value = lua.create_registry_value("hello").unwrap();
+
+    c.bench_function("registry value [get]", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
+                assert_eq!(lua.registry_value::<LuaString>(&value).unwrap(), "hello");
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
 fn userdata_create(c: &mut Criterion) {
     struct UserData(#[allow(unused)] i64);
     impl LuaUserData for UserData {}
@@ -406,6 +423,7 @@ criterion_group! {
         function_async_call_sum,
 
         registry_value_create,
+        registry_value_get,
 
         userdata_create,
         userdata_call_index,

mlua-sys/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mlua-sys"
-version = "0.6.0"
+version = "0.6.1"
 authors = ["Aleksandr Orlenko <zxteam@pm.me>"]
 rust-version = "1.71"
 edition = "2021"
@@ -40,4 +40,7 @@ cfg-if = "1.0"
 pkg-config = "0.3.17"
 lua-src = { version = ">= 546.0.2, < 546.1.0", optional = true }
 luajit-src = { version = ">= 210.5.0, < 210.6.0", optional = true }
-luau0-src = { version = "0.9.0", optional = true }
+luau0-src = { version = "0.10.0", optional = true }
+
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(raw_dylib)'] }

mlua-sys/src/lib.rs

@@ -39,20 +39,25 @@ pub const LUA_MAX_UPVALUES: c_int = 200;
 #[doc(hidden)]
 pub const LUA_TRACEBACK_STACK: c_int = 11;
 
+// Copied from https://github.com/rust-lang/rust/blob/master/library/std/src/sys/pal/common/alloc.rs
 // 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(any(
     target_arch = "x86",
     target_arch = "arm",
+    target_arch = "m68k",
+    target_arch = "csky",
     target_arch = "mips",
+    target_arch = "mips32r6",
     target_arch = "powerpc",
     target_arch = "powerpc64",
     target_arch = "sparc",
-    target_arch = "asmjs",
     target_arch = "wasm32",
     target_arch = "hexagon",
-    all(target_arch = "riscv32", not(target_os = "espidf")),
+    all(
+        target_arch = "riscv32",
+        not(any(target_os = "espidf", target_os = "zkvm"))
+    ),
     all(target_arch = "xtensa", not(target_os = "espidf")),
 ))]
 #[doc(hidden)]
@@ -60,18 +65,20 @@ pub const SYS_MIN_ALIGN: usize = 8;
 #[cfg(any(
     target_arch = "x86_64",
     target_arch = "aarch64",
+    target_arch = "arm64ec",
+    target_arch = "loongarch64",
     target_arch = "mips64",
+    target_arch = "mips64r6",
     target_arch = "s390x",
     target_arch = "sparc64",
     target_arch = "riscv64",
     target_arch = "wasm64",
-    target_arch = "loongarch64",
 ))]
 #[doc(hidden)]
 pub const SYS_MIN_ALIGN: usize = 16;
-// The allocator on the esp-idf platform guarentees 4 byte alignment.
+// The allocator on the esp-idf and zkvm platforms guarantee 4 byte alignment.
 #[cfg(any(
-    all(target_arch = "riscv32", target_os = "espidf"),
+    all(target_arch = "riscv32", any(target_os = "espidf", target_os = "zkvm")),
     all(target_arch = "xtensa", target_os = "espidf"),
 ))]
 #[doc(hidden)]

mlua-sys/src/luau/lua.rs

@@ -288,6 +288,8 @@ extern "C-unwind" {
     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<lua_Destructor>);
     pub fn lua_getuserdatadtor(L: *mut lua_State, tag: c_int) -> Option<lua_Destructor>;
+    pub fn lua_setuserdatametatable(L: *mut lua_State, tag: c_int, idx: c_int);
+    pub fn lua_getuserdatametatable(L: *mut lua_State, tag: c_int);
     pub fn lua_setlightuserdataname(L: *mut lua_State, tag: c_int, name: *const c_char);
     pub fn lua_getlightuserdataname(L: *mut lua_State, tag: c_int) -> *const c_char;
     pub fn lua_clonefunction(L: *mut lua_State, idx: c_int);

mlua-sys/src/luau/luacode.rs

@@ -14,6 +14,7 @@ pub struct lua_CompileOptions {
     pub vectorCtor: *const c_char,
     pub vectorType: *const c_char,
     pub mutableGlobals: *const *const c_char,
+    pub userdataTypes: *const *const c_char,
 }
 
 impl Default for lua_CompileOptions {
@@ -27,6 +28,7 @@ impl Default for lua_CompileOptions {
             vectorCtor: ptr::null(),
             vectorType: ptr::null(),
             mutableGlobals: ptr::null(),
+            userdataTypes: ptr::null(),
         }
     }
 }

src/chunk.rs

@@ -128,6 +128,7 @@ pub struct Compiler {
     vector_ctor: Option<String>,
     vector_type: Option<String>,
     mutable_globals: Vec<String>,
+    userdata_types: Vec<String>,
 }
 
 #[cfg(any(feature = "luau", doc))]
@@ -151,6 +152,7 @@ impl Compiler {
             vector_ctor: None,
             vector_type: None,
             mutable_globals: Vec::new(),
+            userdata_types: Vec::new(),
         }
     }
 
@@ -230,6 +232,13 @@ impl Compiler {
         self
     }
 
+    /// Sets a list of userdata types that will be included in the type information.
+    #[must_use]
+    pub fn set_userdata_types(mut self, types: Vec<String>) -> Self {
+        self.userdata_types = types;
+        self
+    }
+
     /// Compiles the `source` into bytecode.
     pub fn compile(&self, source: impl AsRef<[u8]>) -> Vec<u8> {
         use std::os::raw::c_int;
@@ -245,22 +254,26 @@ impl Compiler {
         let vector_type = vector_type.and_then(|t| CString::new(t).ok());
         let vector_type = vector_type.as_ref();
 
-        let mutable_globals = self
-            .mutable_globals
-            .iter()
-            .map(|name| CString::new(name.clone()).ok())
-            .collect::<Option<Vec<_>>>()
-            .unwrap_or_default();
-        let mut mutable_globals = mutable_globals
-            .iter()
-            .map(|s| s.as_ptr())
-            .collect::<Vec<_>>();
-        let mut mutable_globals_ptr = ptr::null();
-        if !mutable_globals.is_empty() {
-            mutable_globals.push(ptr::null());
-            mutable_globals_ptr = mutable_globals.as_ptr();
+        macro_rules! vec2cstring_ptr {
+            ($name:ident, $name_ptr:ident) => {
+                let $name = self
+                    .$name
+                    .iter()
+                    .map(|name| CString::new(name.clone()).ok())
+                    .collect::<Option<Vec<_>>>()
+                    .unwrap_or_default();
+                let mut $name = $name.iter().map(|s| s.as_ptr()).collect::<Vec<_>>();
+                let mut $name_ptr = ptr::null();
+                if !$name.is_empty() {
+                    $name.push(ptr::null());
+                    $name_ptr = $name.as_ptr();
+                }
+            };
         }
 
+        vec2cstring_ptr!(mutable_globals, mutable_globals_ptr);
+        vec2cstring_ptr!(userdata_types, userdata_types_ptr);
+
         unsafe {
             let mut options = ffi::lua_CompileOptions::default();
             options.optimizationLevel = self.optimization_level as c_int;
@@ -271,6 +284,7 @@ impl Compiler {
             options.vectorCtor = vector_ctor.map_or(ptr::null(), |s| s.as_ptr());
             options.vectorType = vector_type.map_or(ptr::null(), |s| s.as_ptr());
             options.mutableGlobals = mutable_globals_ptr;
+            options.userdataTypes = userdata_types_ptr;
             ffi::luau_compile(source.as_ref(), options)
         }
     }
@@ -327,7 +341,7 @@ impl<'lua, 'a> Chunk<'lua, 'a> {
     ///
     /// This is equivalent to calling the chunk function with no arguments and no return values.
     pub fn exec(self) -> Result<()> {
-        self.call(())?;
+        self.call::<_, ()>(())?;
         Ok(())
     }
 

src/conversion.rs

@@ -453,10 +453,11 @@ impl<'lua> IntoLua<'lua> for &RegistryKey {
             return Err(Error::MismatchedRegistryKey);
         }
 
-        if self.is_nil() {
-            ffi::lua_pushnil(lua.state());
-        } else {
-            ffi::lua_rawgeti(lua.state(), ffi::LUA_REGISTRYINDEX, self.registry_id as _);
+        match self.id() {
+            ffi::LUA_REFNIL => ffi::lua_pushnil(lua.state()),
+            id => {
+                ffi::lua_rawgeti(lua.state(), ffi::LUA_REGISTRYINDEX, id as _);
+            }
         }
         Ok(())
     }

src/error.rs

@@ -101,7 +101,7 @@ pub enum Error {
     /// [`Thread::resume`] was called on an inactive coroutine.
     ///
     /// A coroutine is inactive if its main function has returned or if an error has occurred inside
-    /// the coroutine.
+    /// the coroutine. Already running coroutines are also marked as inactive (unresumable).
     ///
     /// [`Thread::status`] can be used to check if the coroutine can be resumed without causing this
     /// error.

src/lib.rs

@@ -73,7 +73,7 @@
 
 // Deny warnings inside doc tests / examples. When this isn't present, rustdoc doesn't show *any*
 // warnings at all.
-#![doc(test(attr(deny(warnings))))]
+#![doc(test(attr(warn(warnings))))] // FIXME: Remove this when rust-lang/rust#123748 is fixed
 #![cfg_attr(docsrs, feature(doc_cfg))]
 
 #[macro_use]

src/lua.rs

@@ -2049,7 +2049,7 @@ impl Lua {
         T: FromLua<'lua>,
     {
         let state = self.state();
-        let value = unsafe {
+        unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 3)?;
 
@@ -2057,9 +2057,8 @@ impl Lua {
             push_string(state, name.as_bytes(), protect)?;
             ffi::lua_rawget(state, ffi::LUA_REGISTRYINDEX);
 
-            self.pop_value()
-        };
-        T::from_lua(value, self)
+            T::from_stack(-1, self)
+        }
     }
 
     /// Removes a named value in the Lua registry.
@@ -2082,22 +2081,21 @@ impl Lua {
     ///
     /// [`RegistryKey`]: crate::RegistryKey
     pub fn create_registry_value<'lua, T: IntoLua<'lua>>(&'lua self, t: T) -> Result<RegistryKey> {
-        let t = t.into_lua(self)?;
-        if t == Value::Nil {
-            // Special case to skip calling `luaL_ref` and use `LUA_REFNIL` instead
-            let unref_list = unsafe { (*self.extra.get()).registry_unref_list.clone() };
-            return Ok(RegistryKey::new(ffi::LUA_REFNIL, unref_list));
-        }
-
         let state = self.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 4)?;
 
-            self.push_value(t)?;
+            self.push(t)?;
+
+            let unref_list = (*self.extra.get()).registry_unref_list.clone();
+
+            // Check if the value is nil (no need to store it in the registry)
+            if ffi::lua_isnil(state, -1) != 0 {
+                return Ok(RegistryKey::new(ffi::LUA_REFNIL, unref_list));
+            }
 
             // Try to reuse previously allocated slot
-            let unref_list = (*self.extra.get()).registry_unref_list.clone();
             let free_registry_id = mlua_expect!(unref_list.lock(), "unref list poisoned")
                 .as_mut()
                 .and_then(|x| x.pop());
@@ -2107,7 +2105,7 @@ impl Lua {
                 return Ok(RegistryKey::new(registry_id, unref_list));
             }
 
-            // Allocate a new RegistryKey
+            // Allocate a new RegistryKey slot
             let registry_id = if self.unlikely_memory_error() {
                 ffi::luaL_ref(state, ffi::LUA_REGISTRYINDEX)
             } else {
@@ -2131,18 +2129,16 @@ impl Lua {
         }
 
         let state = self.state();
-        let value = match key.is_nil() {
-            true => Value::Nil,
-            false => unsafe {
+        match key.id() {
+            ffi::LUA_REFNIL => T::from_lua(Value::Nil, self),
+            registry_id => unsafe {
                 let _sg = StackGuard::new(state);
                 check_stack(state, 1)?;
 
-                let id = key.registry_id as Integer;
-                ffi::lua_rawgeti(state, ffi::LUA_REGISTRYINDEX, id);
-                self.pop_value()
+                ffi::lua_rawgeti(state, ffi::LUA_REGISTRYINDEX, registry_id as Integer);
+                T::from_stack(-1, self)
             },
-        };
-        T::from_lua(value, self)
+        }
     }
 
     /// Removes a value from the Lua registry.
@@ -2180,29 +2176,32 @@ impl Lua {
         }
 
         let t = t.into_lua(self)?;
-        if t == Value::Nil && key.is_nil() {
-            // Nothing to replace
-            return Ok(());
-        } else if t != Value::Nil && key.registry_id == ffi::LUA_REFNIL {
-            // We cannot update `LUA_REFNIL` slot
-            return Err(Error::runtime("cannot replace nil value with non-nil"));
-        }
 
         let state = self.state();
         unsafe {
             let _sg = StackGuard::new(state);
             check_stack(state, 2)?;
 
-            let id = key.registry_id as Integer;
-            if t == Value::Nil {
-                self.push_value(Value::Integer(id))?;
-                key.set_nil(true);
-            } else {
-                self.push_value(t)?;
-                key.set_nil(false);
+            match (t, key.id()) {
+                (Value::Nil, ffi::LUA_REFNIL) => {
+                    // Do nothing, no need to replace nil with nil
+                }
+                (Value::Nil, registry_id) => {
+                    // Remove the value
+                    ffi::luaL_unref(state, ffi::LUA_REGISTRYINDEX, registry_id);
+                    key.set_id(ffi::LUA_REFNIL);
+                }
+                (value, ffi::LUA_REFNIL) => {
+                    // Allocate a new `RegistryKey`
+                    let new_key = self.create_registry_value(value)?;
+                    key.set_id(new_key.take());
+                }
+                (value, registry_id) => {
+                    // It must be safe to replace the value without triggering memory error
+                    self.push_value(value)?;
+                    ffi::lua_rawseti(state, ffi::LUA_REGISTRYINDEX, registry_id as Integer);
+                }
             }
-            // It must be safe to replace the value without triggering memory error
-            ffi::lua_rawseti(state, ffi::LUA_REGISTRYINDEX, id);
         }
         Ok(())
     }

src/stdlib.rs

@@ -1,5 +1,4 @@
 use std::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign};
-use std::u32;
 
 /// Flags describing the set of lua standard libraries to load.
 #[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]

src/thread.rs

@@ -142,6 +142,10 @@ impl<'lua> Thread<'lua> {
         A: IntoLuaMulti<'lua>,
         R: FromLuaMulti<'lua>,
     {
+        if self.status() != ThreadStatus::Resumable {
+            return Err(Error::CoroutineInactive);
+        }
+
         let lua = self.0.lua;
         let state = lua.state();
         let thread_state = self.state();
@@ -165,10 +169,6 @@ impl<'lua> Thread<'lua> {
         let state = lua.state();
         let thread_state = self.state();
 
-        if self.status() != ThreadStatus::Resumable {
-            return Err(Error::CoroutineInactive);
-        }
-
         let nargs = args.push_into_stack_multi(lua)?;
         if nargs > 0 {
             check_stack(thread_state, nargs)?;
@@ -196,6 +196,10 @@ impl<'lua> Thread<'lua> {
     /// Gets the status of the thread.
     pub fn status(&self) -> ThreadStatus {
         let thread_state = self.state();
+        if thread_state == self.0.lua.state() {
+            // The coroutine is currently running
+            return ThreadStatus::Unresumable;
+        }
         unsafe {
             let status = ffi::lua_status(thread_state);
             if status != ffi::LUA_OK && status != ffi::LUA_YIELD {
@@ -243,6 +247,9 @@ impl<'lua> Thread<'lua> {
     pub fn reset(&self, func: crate::function::Function<'lua>) -> Result<()> {
         let lua = self.0.lua;
         let thread_state = self.state();
+        if thread_state == lua.state() {
+            return Err(Error::runtime("cannot reset a running thread"));
+        }
         unsafe {
             #[cfg(all(feature = "lua54", not(feature = "vendored")))]
             let status = ffi::lua_resetthread(thread_state);

src/types.rs

@@ -4,7 +4,7 @@ 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::atomic::{AtomicI32, Ordering};
 use std::sync::{Arc, Mutex};
 use std::{fmt, mem, ptr};
 
@@ -204,26 +204,25 @@ pub(crate) struct DestructedUserdata;
 /// [`AnyUserData::set_user_value`]: crate::AnyUserData::set_user_value
 /// [`AnyUserData::user_value`]: crate::AnyUserData::user_value
 pub struct RegistryKey {
-    pub(crate) registry_id: c_int,
-    pub(crate) is_nil: AtomicBool,
+    pub(crate) registry_id: AtomicI32,
     pub(crate) unref_list: Arc<Mutex<Option<Vec<c_int>>>>,
 }
 
 impl fmt::Debug for RegistryKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "RegistryKey({})", self.registry_id)
+        write!(f, "RegistryKey({})", self.id())
     }
 }
 
 impl Hash for RegistryKey {
     fn hash<H: Hasher>(&self, state: &mut H) {
-        self.registry_id.hash(state)
+        self.id().hash(state)
     }
 }
 
 impl PartialEq for RegistryKey {
     fn eq(&self, other: &RegistryKey) -> bool {
-        self.registry_id == other.registry_id && Arc::ptr_eq(&self.unref_list, &other.unref_list)
+        self.id() == other.id() && Arc::ptr_eq(&self.unref_list, &other.unref_list)
     }
 }
 
@@ -231,50 +230,47 @@ impl Eq for RegistryKey {}
 
 impl Drop for RegistryKey {
     fn drop(&mut self) {
+        let registry_id = self.id();
         // We don't need to collect nil slot
-        if self.registry_id > ffi::LUA_REFNIL {
+        if registry_id > ffi::LUA_REFNIL {
             let mut unref_list = mlua_expect!(self.unref_list.lock(), "unref list poisoned");
             if let Some(list) = unref_list.as_mut() {
-                list.push(self.registry_id);
+                list.push(registry_id);
             }
         }
     }
 }
 
 impl RegistryKey {
-    // Creates a new instance of `RegistryKey`
+    /// Creates a new instance of `RegistryKey`
     pub(crate) const fn new(id: c_int, unref_list: Arc<Mutex<Option<Vec<c_int>>>>) -> Self {
         RegistryKey {
-            registry_id: id,
-            is_nil: AtomicBool::new(id == ffi::LUA_REFNIL),
+            registry_id: AtomicI32::new(id),
             unref_list,
         }
     }
 
-    // Destroys the `RegistryKey` without adding to the unref list
-    pub(crate) fn take(self) -> c_int {
-        let registry_id = self.registry_id;
+    /// Returns the underlying Lua reference of this `RegistryKey`
+    #[inline(always)]
+    pub fn id(&self) -> c_int {
+        self.registry_id.load(Ordering::Relaxed)
+    }
+
+    /// Sets the unique Lua reference key of this `RegistryKey`
+    #[inline(always)]
+    pub(crate) fn set_id(&self, id: c_int) {
+        self.registry_id.store(id, Ordering::Relaxed);
+    }
+
+    /// Destroys the `RegistryKey` without adding to the unref list
+    pub(crate) fn take(self) -> i32 {
+        let registry_id = self.id();
         unsafe {
             ptr::read(&self.unref_list);
             mem::forget(self);
         }
         registry_id
     }
-
-    // Returns true if this `RegistryKey` holds a nil value
-    #[inline(always)]
-    pub(crate) fn is_nil(&self) -> bool {
-        self.is_nil.load(Ordering::Relaxed)
-    }
-
-    // Marks value of this `RegistryKey` as `Nil`
-    #[inline(always)]
-    pub(crate) fn set_nil(&self, enabled: bool) {
-        // We cannot replace previous value with nil in as this will break
-        // Lua mechanism to find free keys.
-        // Instead, we set a special flag to mark value as nil.
-        self.is_nil.store(enabled, Ordering::Relaxed);
-    }
 }
 
 pub(crate) struct LuaRef<'lua> {

tests/tests.rs

@@ -775,12 +775,11 @@ fn test_replace_registry_value() -> Result<()> {
     lua.replace_registry_value(&key, 123)?;
     assert_eq!(lua.registry_value::<i32>(&key)?, 123);
 
-    // It should be impossible to replace (initial) nil value with non-nil
     let key2 = lua.create_registry_value(Value::Nil)?;
-    match lua.replace_registry_value(&key2, "abc") {
-        Err(Error::RuntimeError(_)) => {}
-        r => panic!("expected RuntimeError, got {r:?}"),
-    }
+    lua.replace_registry_value(&key2, Value::Nil)?;
+    assert_eq!(lua.registry_value::<Value>(&key2)?, Value::Nil);
+    lua.replace_registry_value(&key2, "abc")?;
+    assert_eq!(lua.registry_value::<String>(&key2)?, "abc");
 
     Ok(())
 }

tests/thread.rs

@@ -90,6 +90,19 @@ fn test_thread() -> Result<()> {
         _ => panic!("resuming dead coroutine did not return error"),
     }
 
+    // Already running thread must be unresumable
+    let thread = lua.create_thread(lua.create_function(|lua, ()| {
+        assert_eq!(lua.current_thread().status(), ThreadStatus::Unresumable);
+        let result = lua.current_thread().resume::<_, ()>(());
+        assert!(
+            matches!(result, Err(Error::CoroutineInactive)),
+            "unexpected result: {result:?}",
+        );
+        Ok(())
+    })?)?;
+    let result = thread.resume::<_, ()>(());
+    assert!(result.is_ok(), "unexpected result: {result:?}");
+
     Ok(())
 }
 
@@ -146,6 +159,21 @@ fn test_thread_reset() -> Result<()> {
         assert_eq!(thread.status(), ThreadStatus::Resumable);
     }
 
+    // Try reset running thread
+    let thread = lua.create_thread(lua.create_function(|lua, ()| {
+        let this = lua.current_thread();
+        this.reset(lua.create_function(|_, ()| Ok(()))?)?;
+        Ok(())
+    })?)?;
+    let result = thread.resume::<_, ()>(());
+    assert!(
+        matches!(result, Err(Error::CallbackError{ ref cause, ..})
+            if matches!(cause.as_ref(), Error::RuntimeError(ref err)
+                if err == "cannot reset a running thread")
+        ),
+        "unexpected result: {result:?}",
+    );
+
     Ok(())
 }