feat(ext/http): abort event when request is cancelled (#26781)

```js
Deno.serve(async (req) => {
  const { promise, resolve } = Promise.withResolvers<void>();

  req.signal.addEventListener("abort", () => {
    resolve();
  });

  await promise;

  return new Response("Ok");
});
```

ext/fetch/23_request.js

@@ -281,11 +281,11 @@ class Request {
     if (signal === undefined) {
       const signal = newSignal();
       this[_signalCache] = signal;
-      return signal;
-    }
-
-    if (!signal.aborted && this[_request].isCancelled) {
+      this[_request].onCancel?.(() => {
         signal[signalAbort](signalAbortError);
+      });
+
+      return signal;
     }
 
     return signal;

ext/http/00_serve.ts

@@ -11,10 +11,10 @@ import {
   op_http_cancel,
   op_http_close,
   op_http_close_after_finish,
-  op_http_get_request_cancelled,
   op_http_get_request_headers,
   op_http_get_request_method_and_url,
   op_http_read_request_body,
+  op_http_request_on_cancel,
   op_http_serve,
   op_http_serve_on,
   op_http_set_promise_complete,
@@ -375,11 +375,16 @@ class InnerRequest {
     return this.#external;
   }
 
-  get isCancelled() {
+  onCancel(callback) {
     if (this.#external === null) {
-      return true;
+      callback();
+      return;
     }
-    return op_http_get_request_cancelled(this.#external);
+
+    PromisePrototypeThen(
+      op_http_request_on_cancel(this.#external),
+      callback,
+    );
   }
 }
 

ext/http/http_next.rs

@@ -708,6 +708,19 @@ pub fn op_http_get_request_cancelled(external: *const c_void) -> bool {
   http.cancelled()
 }
 
+#[op2(async)]
+pub async fn op_http_request_on_cancel(external: *const c_void) {
+  let http =
+    // SAFETY: op is called with external.
+    unsafe { clone_external!(external, "op_http_request_on_cancel") };
+  let (tx, rx) = tokio::sync::oneshot::channel();
+
+  http.on_cancel(tx);
+  drop(http);
+
+  rx.await.ok();
+}
+
 /// Returned promise resolves when body streaming finishes.
 /// Call [`op_http_close_after_finish`] when done with the external.
 #[op2(async)]

ext/http/lib.rs

@@ -112,6 +112,7 @@ deno_core::extension!(
     http_next::op_http_close_after_finish,
     http_next::op_http_get_request_header,
     http_next::op_http_get_request_headers,
+    http_next::op_http_request_on_cancel,
     http_next::op_http_get_request_method_and_url<HTTP>,
     http_next::op_http_get_request_cancelled,
     http_next::op_http_read_request_body,

ext/http/service.rs

@@ -27,6 +27,7 @@ use std::rc::Rc;
 use std::task::Context;
 use std::task::Poll;
 use std::task::Waker;
+use tokio::sync::oneshot;
 
 pub type Request = hyper::Request<Incoming>;
 pub type Response = hyper::Response<HttpRecordResponse>;
@@ -211,6 +212,7 @@ pub struct UpgradeUnavailableError;
 
 struct HttpRecordInner {
   server_state: SignallingRc<HttpServerState>,
+  closed_channel: Option<oneshot::Sender<()>>,
   request_info: HttpConnectionProperties,
   request_parts: http::request::Parts,
   request_body: Option<RequestBodyState>,
@@ -276,6 +278,7 @@ impl HttpRecord {
       response_body_finished: false,
       response_body_waker: None,
       trailers: None,
+      closed_channel: None,
       been_dropped: false,
       finished: false,
       needs_close_after_finish: false,
@@ -312,6 +315,10 @@ impl HttpRecord {
     RefMut::map(self.self_mut(), |inner| &mut inner.needs_close_after_finish)
   }
 
+  pub fn on_cancel(&self, sender: oneshot::Sender<()>) {
+    self.self_mut().closed_channel = Some(sender);
+  }
+
   fn recycle(self: Rc<Self>) {
     assert!(
       Rc::strong_count(&self) == 1,
@@ -390,6 +397,9 @@ impl HttpRecord {
     inner.been_dropped = true;
     // The request body might include actual resources.
     inner.request_body.take();
+    if let Some(closed_channel) = inner.closed_channel.take() {
+      let _ = closed_channel.send(());
+    }
   }
 
   /// Complete this record, potentially expunging it if it is fully complete (ie: cancelled as well).

tests/unit/serve_test.ts

@@ -4299,3 +4299,31 @@ Deno.test({
 
   assert(cancelled);
 });
+
+Deno.test({
+  name: "AbortSignal event aborted when request is cancelled",
+}, async () => {
+  const { promise, resolve } = Promise.withResolvers<void>();
+
+  const server = Deno.serve({
+    hostname: "0.0.0.0",
+    port: servePort,
+    onListen: () => resolve(),
+  }, async (request) => {
+    const { promise: promiseAbort, resolve: resolveAbort } = Promise
+      .withResolvers<void>();
+    request.signal.addEventListener("abort", () => resolveAbort());
+    assert(!request.signal.aborted);
+
+    await promiseAbort;
+
+    return new Response("Ok");
+  });
+
+  await promise;
+  await fetch(`http://localhost:${servePort}/`, {
+    signal: AbortSignal.timeout(100),
+  }).catch(() => {});
+
+  await server.shutdown();
+});