fix(core): poll async ops eagerly (denoland#12385)

Currently all async ops are polled lazily, which means that op
initialization code is postponed until control is yielded to the event
loop. This has some weird consequences, e.g.

```js
let listener = Deno.listen(...);
let conn_promise = listener.accept();
listener.close();
// `BadResource` is thrown. A reasonable error would be `Interrupted`.
let conn = await conn_promise;
```

JavaScript promises are expected to be eagerly evaluated. This patch
makes ops actually do that.

cli/tests/unit/http_test.ts

@@ -892,15 +892,13 @@ unitTest(
  respondPromise,
  ]);
 
+ httpConn.close();
  listener.close();
 
  assert(errors.length >= 1);
  for (const error of errors) {
  assertEquals(error.name, "Http");
- assertEquals(
- error.message,
- "connection closed before message completed",
- );
+ assert(error.message.includes("connection"));
  }
  },
 );
@@ -975,44 +973,29 @@ unitTest(
 unitTest(
  { permissions: { net: true } },
  async function droppedConnSenderNoPanic() {
- async function server(listener: Deno.Listener) {
+ async function server() {
+ const listener = Deno.listen({ port: 8000 });
  const conn = await listener.accept();
  const http = Deno.serveHttp(conn);
-
- for (;;) {
- const req = await http.nextRequest();
- if (req == null) break;
-
- nextloop()
- .then(() => {
- http.close();
- return req.respondWith(new Response("boom"));
- })
- .catch(() => {});
- }
-
+ const evt = await http.nextRequest();
+ http.close();
  try {
- http.close();
+ await evt!.respondWith(new Response("boom"));
  } catch {
- "nop";
+ // Ignore error.
  }
-
  listener.close();
  }
 
  async function client() {
- const resp = await fetch("http:https://127.0.0.1:8000/");
- await resp.body?.cancel();
- }
-
- function nextloop() {
- return new Promise((resolve) => setTimeout(resolve, 0));
+ try {
+  const resp = await fetch("http:https://127.0.0.1:8000/");
+  await resp.body?.cancel();
+ } catch {
+  // Ignore error
+ }
  }
 
- async function main() {
- const listener = Deno.listen({ port: 8000 });
- await Promise.all([server(listener), client()]);
- }
- await main();
+ await Promise.all([server(), client()]);
  },
 );

cli/tests/unit/net_test.ts

@@ -117,10 +117,10 @@ unitTest(
  const listener = Deno.listen({ port: 4501 });
  const p = listener.accept();
  listener.close();
+ // TODO(piscisaureus): the error type should be `Interrupted` here, which
+ // gets thrown, but then ext/net catches it and rethrows `BadResource`.
  await assertRejects(
- async () => {
- await p;
- },
+ () => p,
  Deno.errors.BadResource,
  "Listener has been closed",
  );
@@ -141,11 +141,8 @@ unitTest(
  const p = listener.accept();
  listener.close();
  await assertRejects(
- async () => {
- await p;
- },
- Deno.errors.BadResource,
- "Listener has been closed",
+ () => p,
+ Deno.errors.Interrupted,
  );
  },
 );
@@ -173,27 +170,29 @@ unitTest(
  },
 );
 
-// TODO(jsouto): Enable when tokio updates mio to v0.7!
 unitTest(
- { ignore: true, permissions: { read: true, write: true } },
+ {
+ ignore: Deno.build.os === "windows",
+ permissions: { read: true, write: true },
+ },
  async function netUnixConcurrentAccept() {
  const filePath = await Deno.makeTempFile();
  const listener = Deno.listen({ transport: "unix", path: filePath });
  let acceptErrCount = 0;
  const checkErr = (e: Error) => {
- if (e.message === "Listener has been closed") {
+ if (e instanceof Deno.errors.Interrupted) { // "operation canceled"
  assertEquals(acceptErrCount, 1);
- } else if (e.message === "Another accept task is ongoing") {
+ } else if (e instanceof Deno.errors.Busy) { // "Listener already in use"
  acceptErrCount++;
  } else {
- throw new Error("Unexpected error message");
+ throw e;
  }
  };
  const p = listener.accept().catch(checkErr);
  const p1 = listener.accept().catch(checkErr);
  await Promise.race([p, p1]);
  listener.close();
- await [p, p1];
+ await Promise.all([p, p1]);
  assertEquals(acceptErrCount, 1);
  },
 );
@@ -500,11 +499,7 @@ unitTest(
 );
 
 unitTest(
- {
- // FIXME(bartlomieju)
- ignore: true,
- permissions: { net: true },
- },
+ { permissions: { net: true } },
  async function netListenAsyncIterator() {
  const addr = { hostname: "127.0.0.1", port: 3500 };
  const listener = Deno.listen(addr);
@@ -590,8 +585,8 @@ unitTest(
  await conn.write(new Uint8Array([1, 2, 3]));
  }
  } catch (err) {
- assert(!!err);
- assert(err instanceof Deno.errors.BadResource);
+ assert(err);
+ assert(err instanceof Deno.errors.Interrupted);
  }
  }
 

core/lib.rs

@@ -68,6 +68,7 @@ pub use crate::normalize_path::normalize_path;
 pub use crate::ops::serialize_op_result;
 pub use crate::ops::Op;
 pub use crate::ops::OpAsyncFuture;
+pub use crate::ops::OpCall;
 pub use crate::ops::OpFn;
 pub use crate::ops::OpId;
 pub use crate::ops::OpPayload;

core/modules.rs

@@ -722,6 +722,7 @@ impl ModuleMap {
 #[cfg(test)]
 mod tests {
  use super::*;
+ use crate::ops::OpCall;
  use crate::serialize_op_result;
  use crate::JsRuntime;
  use crate::Op;
@@ -1009,7 +1010,7 @@ mod tests {
  let (control, _): (u8, ()) = payload.deserialize().unwrap();
  assert_eq!(control, 42);
  let resp = (0, 1, serialize_op_result(Ok(43), state));
- Op::Async(Box::pin(futures::future::ready(resp)))
+ Op::Async(OpCall::ready(resp))
  };
 
  let mut runtime = JsRuntime::new(RuntimeOptions {

core/ops.rs

@@ -6,6 +6,11 @@ use crate::gotham_state::GothamState;
 use crate::ops_metrics::OpsTracker;
 use crate::resources::ResourceTable;
 use crate::runtime::GetErrorClassFn;
+use futures::future::maybe_done;
+use futures::future::FusedFuture;
+use futures::future::MaybeDone;
+use futures::ready;
+use futures::task::noop_waker;
 use futures::Future;
 use indexmap::IndexMap;
 use rusty_v8 as v8;
@@ -17,10 +22,67 @@ use std::ops::Deref;
 use std::ops::DerefMut;
 use std::pin::Pin;
 use std::rc::Rc;
+use std::task::Context;
+use std::task::Poll;
+
+/// Wrapper around a Future, which causes that Future to be polled immediately.
+/// (Background: ops are stored in a `FuturesUnordered` structure which polls
+/// them, but without the `OpCall` wrapper this doesn't happen until the next
+/// turn of the event loop, which is too late for certain ops.)
+pub struct OpCall<T>(MaybeDone<Pin<Box<dyn Future<Output = T>>>>);
+
+impl<T> OpCall<T> {
+ /// Wraps a future, and polls the inner future immediately.
+ /// This should be the default choice for ops.
+ pub fn eager(fut: impl Future<Output = T> + 'static) -> Self {
+ let boxed = Box::pin(fut) as Pin<Box<dyn Future<Output = T>>>;
+ let mut inner = maybe_done(boxed);
+ let waker = noop_waker();
+ let mut cx = Context::from_waker(&waker);
+ let mut pinned = Pin::new(&mut inner);
+ let _ = pinned.as_mut().poll(&mut cx);
+ Self(inner)
+ }
+
+ /// Wraps a future; the inner future is polled the usual way (lazily).
+ pub fn lazy(fut: impl Future<Output = T> + 'static) -> Self {
+ let boxed = Box::pin(fut) as Pin<Box<dyn Future<Output = T>>>;
+ let inner = maybe_done(boxed);
+ Self(inner)
+ }
+
+ /// Create a future by specifying its output. This is basically the same as
+ /// `async { value }` or `futures::future::ready(value)`.
+ pub fn ready(value: T) -> Self {
+ Self(MaybeDone::Done(value))
+ }
+}
+
+impl<T> Future for OpCall<T> {
+ type Output = T;
+
+ fn poll(
+ self: std::pin::Pin<&mut Self>,
+ cx: &mut std::task::Context<'_>,
+ ) -> std::task::Poll<Self::Output> {
+ let inner = unsafe { &mut self.get_unchecked_mut().0 };
+ let mut pinned = Pin::new(inner);
+ ready!(pinned.as_mut().poll(cx));
+ Poll::Ready(pinned.as_mut().take_output().unwrap())
+ }
+}
+
+impl<F> FusedFuture for OpCall<F>
+where
+ F: Future,
+{
+ fn is_terminated(&self) -> bool {
+ self.0.is_terminated()
+ }
+}
 
 pub type PromiseId = u64;
-pub type OpAsyncFuture =
- Pin<Box<dyn Future<Output = (PromiseId, OpId, OpResult)>>>;
+pub type OpAsyncFuture = OpCall<(PromiseId, OpId, OpResult)>;
 pub type OpFn = dyn Fn(Rc<RefCell<OpState>>, OpPayload) -> Op + 'static;
 pub type OpId = usize;
 

core/ops_json.rs

@@ -1,6 +1,7 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 
 use crate::error::AnyError;
+use crate::ops::OpCall;
 use crate::serialize_op_result;
 use crate::Op;
 use crate::OpFn;
@@ -35,7 +36,7 @@ pub fn void_op_async() -> Box<OpFn> {
  let op_id = payload.op_id;
  let pid = payload.promise_id;
  let op_result = serialize_op_result(Ok(()), state);
- Op::Async(Box::pin(futures::future::ready((pid, op_id, op_result))))
+ Op::Async(OpCall::ready((pid, op_id, op_result)))
  })
 }
 
@@ -127,7 +128,7 @@ where
  use crate::futures::FutureExt;
  let fut = op_fn(state.clone(), a, b)
  .map(move |result| (pid, op_id, serialize_op_result(result, state)));
- Op::Async(Box::pin(fut))
+ Op::Async(OpCall::eager(fut))
  })
 }
 
@@ -159,7 +160,7 @@ where
  use crate::futures::FutureExt;
  let fut = op_fn(state.clone(), a, b)
  .map(move |result| (pid, op_id, serialize_op_result(result, state)));
- Op::AsyncUnref(Box::pin(fut))
+ Op::AsyncUnref(OpCall::eager(fut))
  })
 }
 

core/runtime.rs

@@ -28,24 +28,21 @@ use futures::future::FutureExt;
 use futures::stream::FuturesUnordered;
 use futures::stream::StreamExt;
 use futures::task::AtomicWaker;
-use futures::Future;
 use std::any::Any;
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::convert::TryFrom;
 use std::ffi::c_void;
 use std::mem::forget;
 use std::option::Option;
-use std::pin::Pin;
 use std::rc::Rc;
 use std::sync::Arc;
 use std::sync::Mutex;
 use std::sync::Once;
 use std::task::Context;
 use std::task::Poll;
 
-type PendingOpFuture =
- Pin<Box<dyn Future<Output = (PromiseId, OpId, OpResult)>>>;
+type PendingOpFuture = OpCall<(PromiseId, OpId, OpResult)>;
 
 pub enum Snapshot {
  Static(&'static [u8]),
@@ -1613,6 +1610,7 @@ pub mod tests {
  use crate::ZeroCopyBuf;
  use futures::future::lazy;
  use std::ops::FnOnce;
+ use std::pin::Pin;
  use std::rc::Rc;
  use std::sync::atomic::{AtomicUsize, Ordering};
  use std::sync::Arc;
@@ -1645,16 +1643,15 @@ pub mod tests {
  Mode::Async => {
  assert_eq!(control, 42);
  let resp = (0, 1, serialize_op_result(Ok(43), rc_op_state));
- Op::Async(Box::pin(futures::future::ready(resp)))
+ Op::Async(OpCall::ready(resp))
  }
  Mode::AsyncZeroCopy(has_buffer) => {
  assert_eq!(buf.is_some(), has_buffer);
  if let Some(buf) = buf {
  assert_eq!(buf.len(), 1);
  }
-
- let resp = serialize_op_result(Ok(43), rc_op_state);
- Op::Async(Box::pin(futures::future::ready((0, 1, resp))))
+ let resp = (0, 1, serialize_op_result(Ok(43), rc_op_state));
+ Op::Async(OpCall::ready(resp))
  }
  }
  }

ext/net/01_net.js

@@ -3,7 +3,7 @@
 
 ((window) => {
  const core = window.Deno.core;
- const { BadResource } = core;
+ const { BadResource, Interrupted } = core;
  const {
  PromiseResolve,
  SymbolAsyncIterator,
@@ -124,7 +124,7 @@
  try {
  conn = await this.accept();
  } catch (error) {
- if (error instanceof BadResource) {
+ if (error instanceof BadResource || error instanceof Interrupted) {
  return { value: undefined, done: true };
  }
  throw error;
@@ -191,7 +191,7 @@
  try {
  yield await this.receive();
  } catch (err) {
- if (err instanceof BadResource) {
+ if (err instanceof BadResource || err instanceof Interrupted) {
  break;
  }
  throw err;