fix(core): poll async ops eagerly (#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://127.0.0.1:8000/");
-      await resp.body?.cancel();
+      try {
+        const resp = await fetch("http://127.0.0.1:8000/");
+        await resp.body?.cancel();
+      } catch {
+        // Ignore error
+      }
     }
 
-    function nextloop() {
-      return new Promise((resolve) => setTimeout(resolve, 0));
-    }
-
-    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

@@ -28,7 +28,6 @@ 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;
@@ -36,7 +35,6 @@ 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;
@@ -44,8 +42,7 @@ 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;

ext/web/13_message_port.js

@@ -10,6 +10,7 @@
 
 ((window) => {
   const core = window.Deno.core;
+  const { Interrupted } = core;
   const webidl = window.__bootstrap.webidl;
   const { setEventTargetData } = window.__bootstrap.eventTarget;
   const { defineEventHandler } = window.__bootstrap.event;
@@ -134,10 +135,16 @@
         this[_enabled] = true;
         while (true) {
           if (this[_id] === null) break;
-          const data = await core.opAsync(
-            "op_message_port_recv_message",
-            this[_id],
-          );
+          let data;
+          try {
+            data = await core.opAsync(
+              "op_message_port_recv_message",
+              this[_id],
+            );
+          } catch (err) {
+            if (err instanceof Interrupted) break;
+            throw err;
+          }
           if (data === null) break;
           let message, transferables;
           try {