lib: propagate aborted state to dependent signals before firing events

lib/internal/abort_controller.js

@@ -4,6 +4,7 @@
 // in https://github.com/mysticatea/abort-controller (MIT license)
 
 const {
+  ArrayPrototypePush,
   ObjectAssign,
   ObjectDefineProperties,
   ObjectDefineProperty,
@@ -373,17 +374,36 @@ ObjectDefineProperty(AbortSignal.prototype, SymbolToStringTag, {
 defineEventHandler(AbortSignal.prototype, 'abort');
 
 function abortSignal(signal, reason) {
+  // 1. If signal is aborted, then return.
   if (signal[kAborted]) return;
   signal[kAborted] = true;
+  // 2. Set signal's abort reason to reason if it is given;
+  //    otherwise to a new "AbortError" DOMException.
   signal[kReason] = reason;
+  // 3. Let dependentSignalsToAbort be a new list.
+  const dependentSignalsToAbort = [];
+  // 4. For each dependentSignal of signal's dependent signals:
+  signal[kDependantSignals]?.forEach((s) => {
+    let 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;
+      // 2. Append dependentSignal to dependentSignalsToAbort.
+      ArrayPrototypePush(dependentSignalsToAbort, dependentSignal);
+    }
+  });
+  // 5. Run the abort steps for signal
   const event = new Event('abort', {
     [kTrustEvent]: true,
   });
   signal.dispatchEvent(event);
-  signal[kDependantSignals]?.forEach((s) => {
-    const signalRef = s.deref();
-    if (signalRef) abortSignal(signalRef, reason);
-  });
+  // 6. For each dependentSignal of dependentSignalsToAbort,
+  //    run the abort steps for dependentSignal.
+  for (let i = 0; i < dependentSignalsToAbort.length; i++) {
+    const dependentSignal = dependentSignalsToAbort[i];
+    if (dependentSignal) abortSignal(dependentSignal, reason);
+  };
 }
 
 class AbortController {