Implement thread creation deletion event callback.

src/lib.rs

@@ -113,7 +113,7 @@ pub use crate::traits::{
     FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, LuaNativeFn, LuaNativeFnMut, ObjectLike,
 };
 pub use crate::types::{
-    AppDataRef, AppDataRefMut, Either, Integer, LightUserData, MaybeSend, Number, RegistryKey, VmState,
+    AppDataRef, AppDataRefMut, Either, Integer, LightUserData, MaybeSend, Number, RegistryKey, VmState, ThreadEventInfo
 };
 pub use crate::userdata::{
     AnyUserData, MetaMethod, UserData, UserDataFields, UserDataMetatable, UserDataMethods, UserDataRef,

src/prelude.rs

@@ -14,6 +14,7 @@ pub use crate::{
     UserDataMethods as LuaUserDataMethods, UserDataRef as LuaUserDataRef,
     UserDataRefMut as LuaUserDataRefMut, UserDataRegistry as LuaUserDataRegistry, Value as LuaValue,
     VmState as LuaVmState,
+    ThreadEventInfo as LuaThreadEventInfo
 };
 
 #[cfg(not(feature = "luau"))]

src/state.rs

@@ -21,7 +21,7 @@ use crate::thread::Thread;
 use crate::traits::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti};
 use crate::types::{
     AppDataRef, AppDataRefMut, ArcReentrantMutexGuard, Integer, LuaType, MaybeSend, Number, ReentrantMutex,
-    ReentrantMutexGuard, RegistryKey, VmState, XRc, XWeak,
+    ReentrantMutexGuard, RegistryKey, VmState, XRc, XWeak, ThreadEventInfo
 };
 use crate::userdata::{AnyUserData, UserData, UserDataProxy, UserDataRegistry, UserDataStorage};
 use crate::util::{
@@ -671,6 +671,55 @@ impl Lua {
         }
     }
 
+    /// Sets a callback that will be called by Luau whenever a thread is created/destroyed.
+    /// 
+    /// Often used for keeping track of threads.
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub fn set_thread_event_callback<F>(&self, callback: F)
+    where
+        F: Fn(&Lua, ThreadEventInfo) -> Result<()> + MaybeSend + 'static,
+    {
+        use std::rc::Rc;
+
+        unsafe extern "C-unwind" fn userthread_proc(parent: *mut ffi::lua_State, state: *mut ffi::lua_State) {
+            let extra = ExtraData::get(state);
+            let _guard = StateGuard::new((*extra).raw_lua(), state);
+            let raw_lua: &RawLua = (*extra).raw_lua();
+            raw_lua.push_ref_thread(parent).unwrap();
+            callback_error_ext(state, ptr::null_mut(), move |extra, _| {
+                let userthread_cb = (*extra).userthread_callback.clone();
+                let userthread_cb = mlua_expect!(userthread_cb, "no userthread callback set in userthread_proc");
+                let event_info = match (*extra).raw_lua().pop_value() {
+                    Value::Thread(thr) => ThreadEventInfo::Created(thr),
+                    Value::Nil => ThreadEventInfo::Destroying,
+                    _ => unreachable!()
+                };
+                userthread_cb((*extra).lua(), event_info)
+            });
+        }
+
+        // Set interrupt callback
+        let lua = self.lock();
+        unsafe {
+            (*lua.extra.get()).userthread_callback = Some(Rc::new(callback));
+            (*ffi::lua_callbacks(lua.main_state())).userthread = Some(userthread_proc);
+        }
+    }
+
+    /// Removes any thread event function previously set by `set_thread_event_callback`.
+    ///
+    /// This function has no effect if a callback was not previously set.
+    #[cfg(any(feature = "luau", doc))]
+    #[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
+    pub fn remove_thread_event_callback(&self) {
+        let lua = self.lock();
+        unsafe {
+            (*lua.extra.get()).userthread_callback = None;
+            (*ffi::lua_callbacks(lua.main_state())).userthread = None;
+        }
+    }
+
     /// Sets the warning function to be used by Lua to emit warnings.
     ///
     /// Requires `feature = "lua54"`

src/state/extra.rs

@@ -80,6 +80,8 @@ pub(crate) struct ExtraData {
     pub(super) warn_callback: Option<crate::types::WarnCallback>,
     #[cfg(feature = "luau")]
     pub(super) interrupt_callback: Option<crate::types::InterruptCallback>,
+    #[cfg(feature = "luau")]
+    pub(super) userthread_callback: Option<crate::types::ThreadEventCallback>,
 
     #[cfg(feature = "luau")]
     pub(super) sandboxed: bool,
@@ -177,6 +179,8 @@ impl ExtraData {
             #[cfg(feature = "luau")]
             interrupt_callback: None,
             #[cfg(feature = "luau")]
+            userthread_callback: None,
+            #[cfg(feature = "luau")]
             sandboxed: false,
             #[cfg(feature = "luau")]
             compiler: None,

src/state/raw.rs

@@ -64,7 +64,8 @@ impl Drop for RawLua {
             }
 
             let mem_state = MemoryState::get(self.main_state());
-
+            #[cfg(feature = "luau")] // Fixes a crash during shutdown
+            { (*ffi::lua_callbacks(self.main_state())).userthread = None; }
             ffi::lua_close(self.main_state());
 
             // Deallocate `MemoryState`
@@ -556,6 +557,22 @@ impl RawLua {
         value.push_into_stack(self)
     }
 
+    pub(crate) unsafe fn push_ref_thread(&self, ref_thread: *mut ffi::lua_State) -> Result<()> {
+        let state = self.state();
+        let _sg = StackGuard::new(state);
+        check_stack(state, 2)?;
+        let _sg = StackGuard::new(ref_thread);
+        check_stack(ref_thread, 1)?;
+
+        if self.unlikely_memory_error() {
+            ffi::lua_pushthread(ref_thread)
+        } else {
+            protect_lua!(ref_thread, 0, 1, |ref_thread| ffi::lua_pushthread(ref_thread))?
+        };
+        ffi::lua_xmove(ref_thread, self.ref_thread(), 1);
+        Ok(())
+    }
+
     /// Pushes a `Value` (by reference) onto the Lua stack.
     ///
     /// Uses 2 stack spaces, does not call `checkstack`.

src/types.rs

@@ -6,6 +6,7 @@ use crate::error::Result;
 #[cfg(not(feature = "luau"))]
 use crate::hook::Debug;
 use crate::state::{ExtraData, Lua, RawLua};
+use crate::thread::Thread;
 
 // Re-export mutex wrappers
 pub(crate) use sync::{ArcReentrantMutexGuard, ReentrantMutex, ReentrantMutexGuard, XRc, XWeak};
@@ -73,6 +74,17 @@ pub enum VmState {
     Yield,
 }
 
+/// Information about a thread event.
+/// 
+/// For creating a thread, it contains the thread that created it.
+/// 
+/// This is useful when it is required for tracking all threads and where they come from.
+#[cfg(feature = "luau")]
+pub enum ThreadEventInfo {
+    Created(Thread),
+    Destroying
+}
+
 #[cfg(all(feature = "send", not(feature = "luau")))]
 pub(crate) type HookCallback = Rc<dyn Fn(&Lua, Debug) -> Result<VmState> + Send>;
 
@@ -85,6 +97,13 @@ pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState> + Send>;
 #[cfg(all(not(feature = "send"), feature = "luau"))]
 pub(crate) type InterruptCallback = Rc<dyn Fn(&Lua) -> Result<VmState>>;
 
+#[cfg(all(feature = "send", feature = "luau"))]
+pub(crate) type ThreadEventCallback = Rc<dyn Fn(&Lua, ThreadEventInfo) -> Result<()> + Send>;
+
+#[cfg(all(not(feature = "send"), feature = "luau"))]
+pub(crate) type ThreadEventCallback = Rc<dyn Fn(&Lua, ThreadEventInfo) -> Result<()>>;
+
+
 #[cfg(all(feature = "send", feature = "lua54"))]
 pub(crate) type WarnCallback = Box<dyn Fn(&Lua, &str, bool) -> Result<()> + Send>;