Add Thread::reset() for luajit/lua54

src/ffi/lua.rs

@@ -156,8 +156,13 @@ 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;
+
     #[cfg(feature = "lua54")]
-    pub fn lua_resetthread(L: *mut lua_State) -> c_int;
+    #[link_name = "lua_resetthread"]
+    pub fn lua_resetthread_54(L: *mut lua_State) -> c_int;
+    #[cfg(all(feature = "luajit", feature = "vendored"))]
+    #[link_name = "lua_resetthread"]
+    pub fn lua_resetthread_jit(L: *mut lua_State, th: *mut lua_State);
 
     pub fn lua_atpanic(L: *mut lua_State, panicf: lua_CFunction) -> lua_CFunction;
 
@@ -216,6 +221,17 @@ extern "C" {
     pub fn lua_topointer(L: *mut lua_State, idx: c_int) -> *const c_void;
 }
 
+#[cfg(any(feature = "lua54", all(feature = "luajit", feature = "vendored")))]
+pub unsafe fn lua_resetthread(_L: *mut lua_State, th: *mut lua_State) -> c_int {
+    #[cfg(all(feature = "luajit", feature = "vendored"))]
+    {
+        lua_resetthread_jit(_L, th);
+        LUA_OK
+    }
+    #[cfg(feature = "lua54")]
+    lua_resetthread_54(th)
+}
+
 // Comparison and arithmetic functions
 pub const LUA_OPADD: c_int = 0;
 pub const LUA_OPSUB: c_int = 1;

src/ffi/mod.rs

@@ -160,8 +160,8 @@ pub use self::lua::{
 
 #[cfg(feature = "lua54")]
 pub use self::lua::{
-    lua_getiuservalue, lua_newuserdatauv, lua_resetthread, lua_setcstacklimit, lua_setiuservalue,
-    lua_setwarnf, lua_toclose, lua_warning,
+    lua_getiuservalue, lua_newuserdatauv, lua_setcstacklimit, lua_setiuservalue, lua_setwarnf,
+    lua_toclose, lua_warning,
 };
 
 #[cfg(any(feature = "lua54", feature = "lua53"))]
@@ -170,6 +170,9 @@ pub use self::lua::{lua_isyieldable, lua_version};
 #[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
 pub use self::lua::{lua_callk, lua_pcallk, lua_upvalueid, lua_upvaluejoin, lua_yieldk};
 
+#[cfg(any(feature = "lua54", all(feature = "luajit", feature = "vendored")))]
+pub use self::lua::lua_resetthread;
+
 // auxiliary library types
 pub use self::lauxlib::luaL_Reg;
 

src/thread.rs

@@ -7,6 +7,9 @@ use crate::types::LuaRef;
 use crate::util::{assert_stack, check_stack, pop_error, StackGuard};
 use crate::value::{FromLuaMulti, MultiValue, ToLuaMulti};
 
+#[cfg(any(feature = "lua54", all(feature = "luajit", feature = "vendored"), doc))]
+use crate::function::Function;
+
 #[cfg(feature = "async")]
 use {
     crate::{
@@ -170,6 +173,43 @@ impl<'lua> Thread<'lua> {
         }
     }
 
+    /// Resets a thread
+    ///
+    /// In [Lua 5.4]: cleans its call stack and closes all pending to-be-closed variables.
+    /// Returns a error in case of either the original error that stopped the thread or errors
+    /// in closing methods.
+    ///
+    /// In [LuaJIT]: resets to the initial state of a newly created Lua thread.
+    /// Lua threads in arbitrary states (like yielded or errored) can be reset properly.
+    ///
+    /// Sets a Lua function for the thread afterwards.
+    ///
+    /// Requires `feature = "lua54"` OR `feature = "luajit,vendored"`
+    ///
+    /// [Lua 5.4]: https://www.lua.org/manual/5.4/manual.html#lua_resetthread
+    /// [LuaJIT]: https://github.com/openresty/luajit2#lua_resetthread
+    #[cfg(any(feature = "lua54", all(feature = "luajit", feature = "vendored"), doc))]
+    pub fn reset(&self, func: Function<'lua>) -> Result<()> {
+        let lua = self.0.lua;
+        unsafe {
+            let _sg = StackGuard::new(lua.state);
+            check_stack(lua.state, 2)?;
+
+            lua.push_ref(&self.0);
+            let thread_state = ffi::lua_tothread(lua.state, -1);
+
+            let ret = ffi::lua_resetthread(lua.state, thread_state);
+            if ret != ffi::LUA_OK {
+                return Err(pop_error(thread_state, ret));
+            }
+
+            lua.push_ref(&func.0);
+            ffi::lua_xmove(lua.state, thread_state, 1);
+
+            Ok(())
+        }
+    }
+
     /// Converts Thread to an AsyncThread which implements Future and Stream traits.
     ///
     /// `args` are passed as arguments to the thread function for first call.

src/userdata.rs

@@ -21,7 +21,10 @@ use crate::lua::Lua;
 use crate::table::{Table, TablePairs};
 use crate::types::{LuaRef, MaybeSend};
 use crate::util::{check_stack, get_destructed_userdata_metatable, get_userdata, StackGuard};
-use crate::value::{FromLua, FromLuaMulti, ToLua, ToLuaMulti, Value};
+use crate::value::{FromLua, FromLuaMulti, ToLua, ToLuaMulti};
+
+#[cfg(any(feature = "lua52", feature = "lua51", feature = "luajit"))]
+use crate::value::Value;
 
 /// Kinds of metamethods that can be overridden.
 ///

tests/thread.rs

@@ -93,6 +93,49 @@ fn test_thread() -> Result<()> {
     Ok(())
 }
 
+#[cfg(any(feature = "lua54", all(feature = "luajit", feature = "vendored")))]
+#[test]
+fn test_thread_reset() -> Result<()> {
+    use mlua::{AnyUserData, UserData};
+    use std::sync::Arc;
+
+    let lua = Lua::new();
+
+    struct MyUserData(Arc<()>);
+    impl UserData for MyUserData {}
+
+    let arc = Arc::new(());
+
+    let func: Function = lua.load(r#"function(ud) coroutine.yield(ud) end"#).eval()?;
+    let thread = lua.create_thread(func.clone())?;
+
+    for _ in 0..2 {
+        assert_eq!(thread.status(), ThreadStatus::Resumable);
+        let _ = thread.resume::<_, AnyUserData>(MyUserData(arc.clone()))?;
+        assert_eq!(thread.status(), ThreadStatus::Resumable);
+        assert_eq!(Arc::strong_count(&arc), 2);
+        thread.resume::<_, ()>(())?;
+        assert_eq!(thread.status(), ThreadStatus::Unresumable);
+        thread.reset(func.clone())?;
+        lua.gc_collect()?;
+        assert_eq!(Arc::strong_count(&arc), 1);
+    }
+
+    // Check for errors (Lua 5.4 only)
+    #[cfg(feature = "lua54")]
+    {
+        let func: Function = lua.load(r#"function(ud) error("test error") end"#).eval()?;
+        let thread = lua.create_thread(func.clone())?;
+        let _ = thread.resume::<_, AnyUserData>(MyUserData(arc.clone()));
+        assert_eq!(thread.status(), ThreadStatus::Error);
+        assert_eq!(Arc::strong_count(&arc), 2);
+        assert!(thread.reset(func.clone()).is_err());
+        assert_eq!(thread.status(), ThreadStatus::Error);
+    }
+
+    Ok(())
+}
+
 #[test]
 fn coroutine_from_closure() -> Result<()> {
     let lua = Lua::new();