1use crate::{App, PlatformDispatcher};
2use async_task::Runnable;
3use futures::channel::mpsc;
4use smol::prelude::*;
5use std::mem::ManuallyDrop;
6use std::panic::Location;
7use std::thread::{self, ThreadId};
8use std::{
9 fmt::Debug,
10 marker::PhantomData,
11 mem,
12 num::NonZeroUsize,
13 pin::Pin,
14 rc::Rc,
15 sync::{
16 Arc,
17 atomic::{AtomicUsize, Ordering::SeqCst},
18 },
19 task::{Context, Poll},
20 time::{Duration, Instant},
21};
22use util::TryFutureExt;
23use waker_fn::waker_fn;
24
25#[cfg(any(test, feature = "test-support"))]
26use rand::rngs::StdRng;
27
28/// A pointer to the executor that is currently running,
29/// for spawning background tasks.
30#[derive(Clone)]
31pub struct BackgroundExecutor {
32 #[doc(hidden)]
33 pub dispatcher: Arc<dyn PlatformDispatcher>,
34}
35
36/// A pointer to the executor that is currently running,
37/// for spawning tasks on the main thread.
38///
39/// This is intentionally `!Send` via the `not_send` marker field. This is because
40/// `ForegroundExecutor::spawn` does not require `Send` but checks at runtime that the future is
41/// only polled from the same thread it was spawned from. These checks would fail when spawning
42/// foreground tasks from from background threads.
43#[derive(Clone)]
44pub struct ForegroundExecutor {
45 #[doc(hidden)]
46 pub dispatcher: Arc<dyn PlatformDispatcher>,
47 not_send: PhantomData<Rc<()>>,
48}
49
50/// Task is a primitive that allows work to happen in the background.
51///
52/// It implements [`Future`] so you can `.await` on it.
53///
54/// If you drop a task it will be cancelled immediately. Calling [`Task::detach`] allows
55/// the task to continue running, but with no way to return a value.
56#[must_use]
57#[derive(Debug)]
58pub struct Task<T>(TaskState<T>);
59
60#[derive(Debug)]
61enum TaskState<T> {
62 /// A task that is ready to return a value
63 Ready(Option<T>),
64
65 /// A task that is currently running.
66 Spawned(async_task::Task<T>),
67}
68
69impl<T> Task<T> {
70 /// Creates a new task that will resolve with the value
71 pub fn ready(val: T) -> Self {
72 Task(TaskState::Ready(Some(val)))
73 }
74
75 /// Detaching a task runs it to completion in the background
76 pub fn detach(self) {
77 match self {
78 Task(TaskState::Ready(_)) => {}
79 Task(TaskState::Spawned(task)) => task.detach(),
80 }
81 }
82}
83
84impl<E, T> Task<Result<T, E>>
85where
86 T: 'static,
87 E: 'static + Debug,
88{
89 /// Run the task to completion in the background and log any
90 /// errors that occur.
91 #[track_caller]
92 pub fn detach_and_log_err(self, cx: &App) {
93 let location = core::panic::Location::caller();
94 cx.foreground_executor()
95 .spawn(self.log_tracked_err(*location))
96 .detach();
97 }
98}
99
100impl<T> Future for Task<T> {
101 type Output = T;
102
103 fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
104 match unsafe { self.get_unchecked_mut() } {
105 Task(TaskState::Ready(val)) => Poll::Ready(val.take().unwrap()),
106 Task(TaskState::Spawned(task)) => task.poll(cx),
107 }
108 }
109}
110
111/// A task label is an opaque identifier that you can use to
112/// refer to a task in tests.
113#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
114pub struct TaskLabel(NonZeroUsize);
115
116impl Default for TaskLabel {
117 fn default() -> Self {
118 Self::new()
119 }
120}
121
122impl TaskLabel {
123 /// Construct a new task label.
124 pub fn new() -> Self {
125 static NEXT_TASK_LABEL: AtomicUsize = AtomicUsize::new(1);
126 Self(NEXT_TASK_LABEL.fetch_add(1, SeqCst).try_into().unwrap())
127 }
128}
129
130type AnyLocalFuture<R> = Pin<Box<dyn 'static + Future<Output = R>>>;
131
132type AnyFuture<R> = Pin<Box<dyn 'static + Send + Future<Output = R>>>;
133
134/// BackgroundExecutor lets you run things on background threads.
135/// In production this is a thread pool with no ordering guarantees.
136/// In tests this is simulated by running tasks one by one in a deterministic
137/// (but arbitrary) order controlled by the `SEED` environment variable.
138impl BackgroundExecutor {
139 #[doc(hidden)]
140 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
141 Self { dispatcher }
142 }
143
144 /// Enqueues the given future to be run to completion on a background thread.
145 pub fn spawn<R>(&self, future: impl Future<Output = R> + Send + 'static) -> Task<R>
146 where
147 R: Send + 'static,
148 {
149 self.spawn_internal::<R>(Box::pin(future), None)
150 }
151
152 /// Enqueues the given future to be run to completion on a background thread.
153 /// The given label can be used to control the priority of the task in tests.
154 pub fn spawn_labeled<R>(
155 &self,
156 label: TaskLabel,
157 future: impl Future<Output = R> + Send + 'static,
158 ) -> Task<R>
159 where
160 R: Send + 'static,
161 {
162 self.spawn_internal::<R>(Box::pin(future), Some(label))
163 }
164
165 fn spawn_internal<R: Send + 'static>(
166 &self,
167 future: AnyFuture<R>,
168 label: Option<TaskLabel>,
169 ) -> Task<R> {
170 let dispatcher = self.dispatcher.clone();
171 let (runnable, task) =
172 async_task::spawn(future, move |runnable| dispatcher.dispatch(runnable, label));
173 runnable.schedule();
174 Task(TaskState::Spawned(task))
175 }
176
177 /// Used by the test harness to run an async test in a synchronous fashion.
178 #[cfg(any(test, feature = "test-support"))]
179 #[track_caller]
180 pub fn block_test<R>(&self, future: impl Future<Output = R>) -> R {
181 if let Ok(value) = self.block_internal(false, future, None) {
182 value
183 } else {
184 unreachable!()
185 }
186 }
187
188 /// Block the current thread until the given future resolves.
189 /// Consider using `block_with_timeout` instead.
190 pub fn block<R>(&self, future: impl Future<Output = R>) -> R {
191 if let Ok(value) = self.block_internal(true, future, None) {
192 value
193 } else {
194 unreachable!()
195 }
196 }
197
198 #[cfg(not(any(test, feature = "test-support")))]
199 pub(crate) fn block_internal<Fut: Future>(
200 &self,
201 _background_only: bool,
202 future: Fut,
203 timeout: Option<Duration>,
204 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
205 use std::time::Instant;
206
207 let mut future = Box::pin(future);
208 if timeout == Some(Duration::ZERO) {
209 return Err(future);
210 }
211 let deadline = timeout.map(|timeout| Instant::now() + timeout);
212
213 let unparker = self.dispatcher.unparker();
214 let waker = waker_fn(move || {
215 unparker.unpark();
216 });
217 let mut cx = std::task::Context::from_waker(&waker);
218
219 loop {
220 match future.as_mut().poll(&mut cx) {
221 Poll::Ready(result) => return Ok(result),
222 Poll::Pending => {
223 let timeout =
224 deadline.map(|deadline| deadline.saturating_duration_since(Instant::now()));
225 if !self.dispatcher.park(timeout)
226 && deadline.is_some_and(|deadline| deadline < Instant::now())
227 {
228 return Err(future);
229 }
230 }
231 }
232 }
233 }
234
235 #[cfg(any(test, feature = "test-support"))]
236 #[track_caller]
237 pub(crate) fn block_internal<Fut: Future>(
238 &self,
239 background_only: bool,
240 future: Fut,
241 timeout: Option<Duration>,
242 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
243 use std::sync::atomic::AtomicBool;
244
245 let mut future = Box::pin(future);
246 if timeout == Some(Duration::ZERO) {
247 return Err(future);
248 }
249 let Some(dispatcher) = self.dispatcher.as_test() else {
250 return Err(future);
251 };
252
253 let mut max_ticks = if timeout.is_some() {
254 dispatcher.gen_block_on_ticks()
255 } else {
256 usize::MAX
257 };
258 let unparker = self.dispatcher.unparker();
259 let awoken = Arc::new(AtomicBool::new(false));
260 let waker = waker_fn({
261 let awoken = awoken.clone();
262 move || {
263 awoken.store(true, SeqCst);
264 unparker.unpark();
265 }
266 });
267 let mut cx = std::task::Context::from_waker(&waker);
268
269 loop {
270 match future.as_mut().poll(&mut cx) {
271 Poll::Ready(result) => return Ok(result),
272 Poll::Pending => {
273 if max_ticks == 0 {
274 return Err(future);
275 }
276 max_ticks -= 1;
277
278 if !dispatcher.tick(background_only) {
279 if awoken.swap(false, SeqCst) {
280 continue;
281 }
282
283 if !dispatcher.parking_allowed() {
284 let mut backtrace_message = String::new();
285 let mut waiting_message = String::new();
286 if let Some(backtrace) = dispatcher.waiting_backtrace() {
287 backtrace_message =
288 format!("\nbacktrace of waiting future:\n{:?}", backtrace);
289 }
290 if let Some(waiting_hint) = dispatcher.waiting_hint() {
291 waiting_message = format!("\n waiting on: {}\n", waiting_hint);
292 }
293 panic!(
294 "parked with nothing left to run{waiting_message}{backtrace_message}",
295 )
296 }
297 self.dispatcher.park(None);
298 }
299 }
300 }
301 }
302 }
303
304 /// Block the current thread until the given future resolves
305 /// or `duration` has elapsed.
306 pub fn block_with_timeout<Fut: Future>(
307 &self,
308 duration: Duration,
309 future: Fut,
310 ) -> Result<Fut::Output, impl Future<Output = Fut::Output> + use<Fut>> {
311 self.block_internal(true, future, Some(duration))
312 }
313
314 /// Scoped lets you start a number of tasks and waits
315 /// for all of them to complete before returning.
316 pub async fn scoped<'scope, F>(&self, scheduler: F)
317 where
318 F: FnOnce(&mut Scope<'scope>),
319 {
320 let mut scope = Scope::new(self.clone());
321 (scheduler)(&mut scope);
322 let spawned = mem::take(&mut scope.futures)
323 .into_iter()
324 .map(|f| self.spawn(f))
325 .collect::<Vec<_>>();
326 for task in spawned {
327 task.await;
328 }
329 }
330
331 /// Get the current time.
332 ///
333 /// Calling this instead of `std::time::Instant::now` allows the use
334 /// of fake timers in tests.
335 pub fn now(&self) -> Instant {
336 self.dispatcher.now()
337 }
338
339 /// Returns a task that will complete after the given duration.
340 /// Depending on other concurrent tasks the elapsed duration may be longer
341 /// than requested.
342 pub fn timer(&self, duration: Duration) -> Task<()> {
343 if duration.is_zero() {
344 return Task::ready(());
345 }
346 let (runnable, task) = async_task::spawn(async move {}, {
347 let dispatcher = self.dispatcher.clone();
348 move |runnable| dispatcher.dispatch_after(duration, runnable)
349 });
350 runnable.schedule();
351 Task(TaskState::Spawned(task))
352 }
353
354 /// in tests, start_waiting lets you indicate which task is waiting (for debugging only)
355 #[cfg(any(test, feature = "test-support"))]
356 pub fn start_waiting(&self) {
357 self.dispatcher.as_test().unwrap().start_waiting();
358 }
359
360 /// in tests, removes the debugging data added by start_waiting
361 #[cfg(any(test, feature = "test-support"))]
362 pub fn finish_waiting(&self) {
363 self.dispatcher.as_test().unwrap().finish_waiting();
364 }
365
366 /// in tests, run an arbitrary number of tasks (determined by the SEED environment variable)
367 #[cfg(any(test, feature = "test-support"))]
368 pub fn simulate_random_delay(&self) -> impl Future<Output = ()> + use<> {
369 self.dispatcher.as_test().unwrap().simulate_random_delay()
370 }
371
372 /// in tests, indicate that a given task from `spawn_labeled` should run after everything else
373 #[cfg(any(test, feature = "test-support"))]
374 pub fn deprioritize(&self, task_label: TaskLabel) {
375 self.dispatcher.as_test().unwrap().deprioritize(task_label)
376 }
377
378 /// in tests, move time forward. This does not run any tasks, but does make `timer`s ready.
379 #[cfg(any(test, feature = "test-support"))]
380 pub fn advance_clock(&self, duration: Duration) {
381 self.dispatcher.as_test().unwrap().advance_clock(duration)
382 }
383
384 /// in tests, run one task.
385 #[cfg(any(test, feature = "test-support"))]
386 pub fn tick(&self) -> bool {
387 self.dispatcher.as_test().unwrap().tick(false)
388 }
389
390 /// in tests, run all tasks that are ready to run. If after doing so
391 /// the test still has outstanding tasks, this will panic. (See also `allow_parking`)
392 #[cfg(any(test, feature = "test-support"))]
393 pub fn run_until_parked(&self) {
394 self.dispatcher.as_test().unwrap().run_until_parked()
395 }
396
397 /// in tests, prevents `run_until_parked` from panicking if there are outstanding tasks.
398 /// This is useful when you are integrating other (non-GPUI) futures, like disk access, that
399 /// do take real async time to run.
400 #[cfg(any(test, feature = "test-support"))]
401 pub fn allow_parking(&self) {
402 self.dispatcher.as_test().unwrap().allow_parking();
403 }
404
405 /// undoes the effect of [`allow_parking`].
406 #[cfg(any(test, feature = "test-support"))]
407 pub fn forbid_parking(&self) {
408 self.dispatcher.as_test().unwrap().forbid_parking();
409 }
410
411 /// adds detail to the "parked with nothing let to run" message.
412 #[cfg(any(test, feature = "test-support"))]
413 pub fn set_waiting_hint(&self, msg: Option<String>) {
414 self.dispatcher.as_test().unwrap().set_waiting_hint(msg);
415 }
416
417 /// in tests, returns the rng used by the dispatcher and seeded by the `SEED` environment variable
418 #[cfg(any(test, feature = "test-support"))]
419 pub fn rng(&self) -> StdRng {
420 self.dispatcher.as_test().unwrap().rng()
421 }
422
423 /// How many CPUs are available to the dispatcher.
424 pub fn num_cpus(&self) -> usize {
425 #[cfg(any(test, feature = "test-support"))]
426 return 4;
427
428 #[cfg(not(any(test, feature = "test-support")))]
429 return num_cpus::get();
430 }
431
432 /// Whether we're on the main thread.
433 pub fn is_main_thread(&self) -> bool {
434 self.dispatcher.is_main_thread()
435 }
436
437 #[cfg(any(test, feature = "test-support"))]
438 /// in tests, control the number of ticks that `block_with_timeout` will run before timing out.
439 pub fn set_block_on_ticks(&self, range: std::ops::RangeInclusive<usize>) {
440 self.dispatcher.as_test().unwrap().set_block_on_ticks(range);
441 }
442}
443
444/// ForegroundExecutor runs things on the main thread.
445impl ForegroundExecutor {
446 /// Creates a new ForegroundExecutor from the given PlatformDispatcher.
447 pub fn new(dispatcher: Arc<dyn PlatformDispatcher>) -> Self {
448 Self {
449 dispatcher,
450 not_send: PhantomData,
451 }
452 }
453
454 /// Enqueues the given Task to run on the main thread at some point in the future.
455 #[track_caller]
456 pub fn spawn<R>(&self, future: impl Future<Output = R> + 'static) -> Task<R>
457 where
458 R: 'static,
459 {
460 let dispatcher = self.dispatcher.clone();
461
462 #[track_caller]
463 fn inner<R: 'static>(
464 dispatcher: Arc<dyn PlatformDispatcher>,
465 future: AnyLocalFuture<R>,
466 ) -> Task<R> {
467 let (runnable, task) = spawn_local_with_source_location(future, move |runnable| {
468 dispatcher.dispatch_on_main_thread(runnable)
469 });
470 runnable.schedule();
471 Task(TaskState::Spawned(task))
472 }
473 inner::<R>(dispatcher, Box::pin(future))
474 }
475}
476
477/// Variant of `async_task::spawn_local` that includes the source location of the spawn in panics.
478///
479/// Copy-modified from:
480/// https://github.com/smol-rs/async-task/blob/ca9dbe1db9c422fd765847fa91306e30a6bb58a9/src/runnable.rs#L405
481#[track_caller]
482fn spawn_local_with_source_location<Fut, S>(
483 future: Fut,
484 schedule: S,
485) -> (Runnable<()>, async_task::Task<Fut::Output, ()>)
486where
487 Fut: Future + 'static,
488 Fut::Output: 'static,
489 S: async_task::Schedule<()> + Send + Sync + 'static,
490{
491 #[inline]
492 fn thread_id() -> ThreadId {
493 std::thread_local! {
494 static ID: ThreadId = thread::current().id();
495 }
496 ID.try_with(|id| *id)
497 .unwrap_or_else(|_| thread::current().id())
498 }
499
500 struct Checked<F> {
501 id: ThreadId,
502 inner: ManuallyDrop<F>,
503 location: &'static Location<'static>,
504 }
505
506 impl<F> Drop for Checked<F> {
507 fn drop(&mut self) {
508 assert!(
509 self.id == thread_id(),
510 "local task dropped by a thread that didn't spawn it. Task spawned at {}",
511 self.location
512 );
513 unsafe {
514 ManuallyDrop::drop(&mut self.inner);
515 }
516 }
517 }
518
519 impl<F: Future> Future for Checked<F> {
520 type Output = F::Output;
521
522 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
523 assert!(
524 self.id == thread_id(),
525 "local task polled by a thread that didn't spawn it. Task spawned at {}",
526 self.location
527 );
528 unsafe { self.map_unchecked_mut(|c| &mut *c.inner).poll(cx) }
529 }
530 }
531
532 // Wrap the future into one that checks which thread it's on.
533 let future = Checked {
534 id: thread_id(),
535 inner: ManuallyDrop::new(future),
536 location: Location::caller(),
537 };
538
539 unsafe { async_task::spawn_unchecked(future, schedule) }
540}
541
542/// Scope manages a set of tasks that are enqueued and waited on together. See [`BackgroundExecutor::scoped`].
543pub struct Scope<'a> {
544 executor: BackgroundExecutor,
545 futures: Vec<Pin<Box<dyn Future<Output = ()> + Send + 'static>>>,
546 tx: Option<mpsc::Sender<()>>,
547 rx: mpsc::Receiver<()>,
548 lifetime: PhantomData<&'a ()>,
549}
550
551impl<'a> Scope<'a> {
552 fn new(executor: BackgroundExecutor) -> Self {
553 let (tx, rx) = mpsc::channel(1);
554 Self {
555 executor,
556 tx: Some(tx),
557 rx,
558 futures: Default::default(),
559 lifetime: PhantomData,
560 }
561 }
562
563 /// How many CPUs are available to the dispatcher.
564 pub fn num_cpus(&self) -> usize {
565 self.executor.num_cpus()
566 }
567
568 /// Spawn a future into this scope.
569 pub fn spawn<F>(&mut self, f: F)
570 where
571 F: Future<Output = ()> + Send + 'a,
572 {
573 let tx = self.tx.clone().unwrap();
574
575 // SAFETY: The 'a lifetime is guaranteed to outlive any of these futures because
576 // dropping this `Scope` blocks until all of the futures have resolved.
577 let f = unsafe {
578 mem::transmute::<
579 Pin<Box<dyn Future<Output = ()> + Send + 'a>>,
580 Pin<Box<dyn Future<Output = ()> + Send + 'static>>,
581 >(Box::pin(async move {
582 f.await;
583 drop(tx);
584 }))
585 };
586 self.futures.push(f);
587 }
588}
589
590impl Drop for Scope<'_> {
591 fn drop(&mut self) {
592 self.tx.take().unwrap();
593
594 // Wait until the channel is closed, which means that all of the spawned
595 // futures have resolved.
596 self.executor.block(self.rx.next());
597 }
598}