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lib: fix AbortSignal.any() observed-composite leak #64481

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lib: fix AbortSignal.any() observed-composite leak #64481

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7 changes: 7 additions & 0 deletions lib/internal/abort_controller.js
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Original file line number Diff line number Diff line change
Expand Up @@ -522,6 +522,13 @@ function abortSignal(signal, reason) {
for (let i = 0; i < dependentSignalsToAbort.length; i++) {
const dependentSignal = dependentSignalsToAbort[i];
runAbort(dependentSignal);
// A transitively-aborted dependent signal can never abort again, so there
// is no longer any reason to keep it alive. Dropping it from
// gcPersistentSignals lets it be collected, which in turn prunes its
// WeakRef from its sources' kDependantSignals sets. Otherwise, an observed
// composite that follows a long-lived source stays retained forever and
// its entry accumulates in that source's kDependantSignals.
gcPersistentSignals.delete(dependentSignal);
}

// Clean up the signal from gcPersistentSignals
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31 changes: 31 additions & 0 deletions test/parallel/test-abortsignal-drop-settled-signals.mjs
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Expand Up @@ -142,6 +142,37 @@ describe('when there is a long-lived signal', () => {

run(1);
});

it('drops observed dependent signals once they are transitively aborted', async () => {
const longLived = new AbortController();
const handler = () => {};
const size = () => {
const sym = Object.getOwnPropertySymbols(longLived.signal).find(
(s) => s.toString() === 'Symbol(kDependantSignals)'
);
return sym ? longLived.signal[sym].size : 0;
};

// Each composite observes the long-lived source and a per-request source,
// then is aborted through the per-request source without ever removing its
// listener. The aborted composites can never fire again, so the long-lived
// source's dependant set must not accumulate them. Using a helper keeps the
// last iteration's signals from lingering on the stack for the assertion.
const createObservedAbortedComposite = () => {
const perReq = new AbortController();
const composite = AbortSignal.any([perReq.signal, longLived.signal]);
composite.addEventListener('abort', handler);
perReq.abort();
};
for (let i = 0; i < limit; i++) {
createObservedAbortedComposite();
}

await gcUntil(
'observed dependents are dropped after transitive abort',
() => size() === 0,
);
});
});

it('does not prevent source signal from being GCed if it is short-lived', (t, done) => {
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