lib: settle signals when abortcontroller is GCed

lib/internal/abort_controller.js

@@ -84,6 +84,32 @@ function lazyMessageChannel() {
 }
 
 const clearTimeoutRegistry = new SafeFinalizationRegistry(clearTimeout);
+const abortControllerSignalFinalizer = new SafeFinalizationRegistry(({ signalWeakRef }) => {
+  // WIP on https://docs.google.com/document/d/1LvmsBLV85p-PhSGvTH-YwgD6onuhh1VXLg8jPlH32H4/edit?pli=1&tab=t.0#heading=h.7ut6obnf9fz0
+  // Remove ac.signal from composed signals
+  // If not source signal remains in the composed signal, let it be GCed
+  console.log('ac was collected', signalWeakRef.deref());
+
+  const signal = signalWeakRef.deref();
+  if (signal === undefined) {
+    return;
+  }
+
+  signal[kDependantSignals]?.forEach((ref) => {
+    const dependantSignal = ref.deref();
+
+    if (dependantSignal === undefined) {
+      return;
+    }
+
+    dependantSignal[kSourceSignals]?.delete(signalWeakRef);
+
+    if (dependantSignal[kSourceSignals]?.size === 0) {
+      gcPersistentSignals.delete(dependantSignal);
+    }
+  });
+});
+
 const dependantSignalsCleanupRegistry = new SafeFinalizationRegistry((signalWeakRef) => {
   const signal = signalWeakRef.deref();
   if (signal === undefined) {
@@ -434,6 +460,9 @@ class AbortController {
    */
   get signal() {
     this.#signal ??= new AbortSignal(kDontThrowSymbol);
+
+    abortControllerSignalFinalizer.register(this, { signal: new SafeWeakRef(this.#signal) });
+
     return this.#signal;
   }