lib: propagate aborted state to dependent signals before firing events

lib/internal/abort_controller.js

@@ -4,12 +4,14 @@
 // in https://github.com/mysticatea/abort-controller (MIT license)
 
 const {
+  ArrayPrototypePush,
   ObjectAssign,
   ObjectDefineProperties,
   ObjectDefineProperty,
   PromiseResolve,
   SafeFinalizationRegistry,
   SafeSet,
+  SetPrototypeForEach,
   Symbol,
   SymbolToStringTag,
   WeakRef,
@@ -372,18 +374,48 @@ ObjectDefineProperty(AbortSignal.prototype, SymbolToStringTag, {
 
 defineEventHandler(AbortSignal.prototype, 'abort');
 
+// https://dom.spec.whatwg.org/#dom-abortsignal-abort
 function abortSignal(signal, reason) {
+  // 1. If signal is aborted, then return.
   if (signal[kAborted]) return;
+
+  // 2. Set signal's abort reason to reason if it is given;
+  //    otherwise to a new "AbortError" DOMException.
   signal[kAborted] = true;
   signal[kReason] = reason;
+  // 3. Let dependentSignalsToAbort be a new list.
+  const dependentSignalsToAbort = [];
+  // 4. For each dependentSignal of signal's dependent signals:
+  if (signal[kDependantSignals]) {
+    // Equivalent to Set.prototype.forEach
+    SetPrototypeForEach(signal[kDependantSignals], (s) => {
+      const dependentSignal = s.deref();
+      // 1. If dependentSignal is not aborted, then:
+      if (dependentSignal && !dependentSignal[kAborted]) {
+        // 1. Set dependentSignal's abort reason to signal's abort reason.
+        dependentSignal[kReason] = reason;
+        dependentSignal[kAborted] = true;
+        // 2. Append dependentSignal to dependentSignalsToAbort.
+        ArrayPrototypePush(dependentSignalsToAbort, dependentSignal);
+      }
+    });
+  }
+  // 5. Run the abort steps for signal
+  runAbort(signal);
+  // 6. For each dependentSignal of dependentSignalsToAbort,
+  //    run the abort steps for dependentSignal.
+  for (let i = 0; i < dependentSignalsToAbort.length; i++) {
+    const dependentSignal = dependentSignalsToAbort[i];
+    runAbort(dependentSignal);
+  };
+}
+
+// To run the abort steps for an AbortSignal signal
+function runAbort(signal) {
   const event = new Event('abort', {
     [kTrustEvent]: true,
   });
   signal.dispatchEvent(event);
-  signal[kDependantSignals]?.forEach((s) => {
-    const signalRef = s.deref();
-    if (signalRef) abortSignal(signalRef, reason);
-  });
 }
 
 class AbortController {

test/parallel/test-abortsignal-any.mjs

@@ -118,4 +118,45 @@ describe('AbortSignal.any()', { concurrency: !process.env.TEST_PARALLEL }, () =>
     controller.abort();
     assert.strictEqual(result, 1);
   });
+
+  // Refs: https://github.com/web-platform-tests/wpt/pull/47653
+  it('marks dependent signals aborted before abort events fire', () => {
+    const controller = new AbortController();
+    const signal1 = AbortSignal.any([controller.signal]);
+    const signal2 = AbortSignal.any([signal1]);
+    let eventFired = false;
+
+    controller.signal.addEventListener('abort', () => {
+      const signal3 = AbortSignal.any([signal2]);
+      assert(controller.signal.aborted);
+      assert(signal1.aborted);
+      assert(signal2.aborted);
+      assert(signal3.aborted);
+      eventFired = true;
+    });
+
+    controller.abort();
+    assert(eventFired, 'event fired');
+  });
+
+  // Refs: https://github.com/web-platform-tests/wpt/pull/47653
+  it('aborts dependent signals correctly for reentrant aborts', () => {
+    const controller1 = new AbortController();
+    const controller2 = new AbortController();
+    const signal = AbortSignal.any([controller1.signal, controller2.signal]);
+    let count = 0;
+
+    controller1.signal.addEventListener('abort', () => {
+      controller2.abort('reason 2');
+    });
+
+    signal.addEventListener('abort', () => {
+      count++;
+    });
+
+    controller1.abort('reason 1');
+    assert.strictEqual(count, 1);
+    assert(signal.aborted);
+    assert.strictEqual(signal.reason, 'reason 1');
+  });
 });