goofy ahh once cell function storage code

src/runner/script_signal.rs

@@ -44,6 +44,7 @@ pub struct ScriptSignal{
 	callbacks:RcFunctionList,
 	once:RcFunctionList,
 	wait:Rc<RefCell<Vec<mlua::Thread>>>,
+	wait_function:std::cell::OnceCell<mlua::Function>,
 }
 pub struct ScriptConnection{
 	connection:RcFunctionList,
@@ -55,6 +56,7 @@ impl ScriptSignal{
 			callbacks:RcFunctionList::new(),
 			once:RcFunctionList::new(),
 			wait:Rc::new(RefCell::new(Vec::new())),
+			wait_function:std::cell::OnceCell::new(),
 		}
 	}
 	pub fn fire(&self,args:&mlua::MultiValue){
@@ -94,7 +96,45 @@ impl ScriptConnection{
 	}
 }
 
+fn wait_thread(lua:&mlua::Lua,this:ScriptSignal)->Result<(),mlua::Error>{
+	Ok(this.wait(lua.current_thread()))
+}
+
+// This is used to avoid calling coroutine.yield from the rust side.
+const LUA_WAIT:&str=
+"local coroutine_yield=coroutine.yield
+local wait_thread=wait_thread
+return function()
+	wait_thread()
+	return coroutine_yield()
+end";
+
 impl mlua::UserData for ScriptSignal{
+	fn add_fields<F:mlua::UserDataFields<Self>>(fields:&mut F){
+		fields.add_field_method_get("Wait",|lua,this|{
+			Ok(match this.wait_function.get(){
+				Some(f)=>f.clone(),
+				None=>{
+					let coroutine_table=lua.globals().get::<mlua::Table>("coroutine")?;
+					let wait_thread=lua.create_function(wait_thread)?;
+
+					//create wait function environment
+					let wait_env=lua.create_table()?;
+					wait_env.raw_set("coroutine",coroutine_table)?;
+					wait_env.raw_set("wait_thread",wait_thread)?;
+
+					//construct wait function from Lua code
+					let wait=lua.load(LUA_WAIT)
+					.set_name("wait")
+					.set_environment(wait_env)
+					.call::<mlua::Function>(())?;
+
+					this.wait_function.set(wait.clone()).unwrap();
+					wait
+				}
+			})
+		});
+	}
 	fn add_methods<M:mlua::UserDataMethods<Self>>(methods:&mut M){
 		methods.add_method("Connect",|_lua,this,f:mlua::Function|
 			Ok(this.connect(f))
@@ -102,10 +142,6 @@ impl mlua::UserData for ScriptSignal{
 		methods.add_method("Once",|_lua,this,f:mlua::Function|
 			Ok(this.once(f))
 		);
-		methods.add_method("Wait",|lua,this,()|
-			Ok(this.wait(lua.current_thread()))
-			todo!("coroutine.yield");
-		);
 		// Fire is not allowed to be called from Lua
 		// methods.add_method("Fire",|_lua,this,args:mlua::MultiValue|
 		// 	Ok(this.fire(args))