add function to tick local executors

Author: hymm

crates/bevy_tasks/src/task_pool.rs

@@ -317,6 +317,24 @@ impl TaskPool {
     {
         Task::new(TaskPool::LOCAL_EXECUTOR.with(|executor| executor.spawn(future)))
     }
+
+    /// Runs a function with the local executor. Typically used to tick
+    /// the local executor on the main thread as it needs to share time with
+    /// other things.
+    ///
+    /// ```rust
+    /// use bevy_tasks::TaskPool;
+    ///
+    /// TaskPool::new().with_local_executor(|local_executor| {
+    ///     local_executor.try_tick();
+    /// });
+    /// ```
+    pub fn with_local_executor<F, R>(&self, f: F) -> R
+    where
+        F: FnOnce(&async_executor::LocalExecutor) -> R,
+    {
+        Self::LOCAL_EXECUTOR.with(f)
+    }
 }
 
 impl Default for TaskPool {

crates/bevy_tasks/src/usages.rs

@@ -109,3 +109,27 @@ impl Deref for IoTaskPool {
         &self.0
     }
 }
+
+/// Used by `bevy_app` to tick the global tasks pools on the main thread.
+pub fn tick_global_task_pools_on_main_thread() {
+    COMPUTE_TASK_POOL
+        .get()
+        .unwrap()
+        .with_local_executor(|compute_local_executor| {
+            ASYNC_COMPUTE_TASK_POOL
+                .get()
+                .unwrap()
+                .with_local_executor(|async_local_executor| {
+                    IO_TASK_POOL
+                        .get()
+                        .unwrap()
+                        .with_local_executor(|io_local_executor| {
+                            for _ in 0..20 {
+                                compute_local_executor.try_tick();
+                                async_local_executor.try_tick();
+                                io_local_executor.try_tick();
+                            }
+                        });
+                });
+        });
+}