Fix scheduler loop causing infinitely running process

crates/mlua-luau-scheduler/src/scheduler.rs

@@ -8,7 +8,7 @@ use std::{
     thread::panicking,
 };
 
-use futures_lite::prelude::*;
+use futures_lite::{future::yield_now, prelude::*};
 use mlua::prelude::*;
 
 use async_executor::{Executor, LocalExecutor};
@@ -369,23 +369,28 @@ impl<'lua> Scheduler<'lua> {
 
                 // 5
                 let mut num_processed = 0;
-                let span_tick = trace_span!("Scheduler::tick");
-                let fut_tick = async {
-                    local_exec.tick().await;
-                    // NOTE: Try to do as much work as possible instead of just a single tick()
-                    num_processed += 1;
-                    while local_exec.try_tick() {
-                        num_processed += 1;
-                    }
-                };
+                // let span_tick = trace_span!("Scheduler::tick");
+                // let fut_tick = async {
+                //     local_exec.tick().await;
+                //     // NOTE: Try to do as much work as possible instead of just a single tick()
+                //     num_processed += 1;
+                //     while local_exec.try_tick() {
+                //         num_processed += 1;
+                //     }
+                // };
+                local_exec
+                    .run(
+                        fut_exit.or(fut_spawn).or(fut_defer).or(fut_futs).or(async {
+                            local_exec.tick().await; // weird but is required to preserve scheduler ordering
+
+                            if !local_exec.is_empty() {
+                                yield_now().await;
+                            }
+                        }), // .or(fut_tick.instrument(span_tick.or_current())),
+                    )
+                    .await;
 
                 // 1 + 2 + 3 + 4 + 5
-                fut_exit
-                    .or(fut_spawn)
-                    .or(fut_defer)
-                    .or(fut_futs)
-                    .or(fut_tick.instrument(span_tick.or_current()))
-                    .await;
 
                 // Check if we should exit
                 if self.exit.get().is_some() {

tests/task/defer.luau

@@ -41,21 +41,29 @@ end)
 task.wait()
 assert(flag3 == 3, "Defer should run after spawned threads")
 
--- Delay should be able to be nested
+-- Defer should be able to be nested
 
 local flag4: boolean = false
-task.delay(0.05, function()
+task.defer(function()
 	local function nested3()
-		task.delay(0.05, function()
+		task.defer(function()
+			task.wait(0.05)
 			flag4 = true
 		end)
 	end
 	local function nested2()
-		task.delay(0.05, nested3)
+		task.defer(function()
+			task.wait(0.05)
+			nested3()
+		end)
 	end
 	local function nested1()
-		task.delay(0.05, nested2)
+		task.defer(function()
+			task.wait(0.05)
+			nested2()
+		end)
 	end
+	task.wait(0.05)
 	nested1()
 end)
 task.wait(0.25)

tests/task/delay.luau

@@ -28,33 +28,25 @@ assert(flag, "Delay should work with yielding (1)")
 task.wait(0.1)
 assert(not flag2, "Delay should work with yielding (2)")
 
--- Defer should be able to be nested
+-- Delay should be able to be nested
 
 local flag4: boolean = false
-task.defer(function()
+task.delay(0.05, function()
 	local function nested3()
-		task.defer(function()
-			task.wait(0.05)
+		task.delay(0.05, function()
 			flag4 = true
 		end)
 	end
 	local function nested2()
-		task.defer(function()
-			task.wait(0.05)
-			nested3()
-		end)
+		task.delay(0.05, nested3)
 	end
 	local function nested1()
-		task.defer(function()
-			task.wait(0.05)
-			nested2()
-		end)
+		task.delay(0.05, nested2)
 	end
-	task.wait(0.05)
 	nested1()
 end)
 task.wait(0.25)
-assert(flag4, "Defer should work with nesting")
+assert(flag4, "Delay should work with nesting")
 
 -- Varargs should get passed correctly