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lib: add aborted() utility function #46494

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merged 26 commits into from Feb 7, 2023
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18 changes: 18 additions & 0 deletions lib/internal/abort_controller.js
Expand Up @@ -13,6 +13,7 @@ const {
Symbol,
SymbolToStringTag,
WeakRef,
PromiseResolve,
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} = primordials;

const {
Expand All @@ -22,11 +23,13 @@ const {
kTrustEvent,
kNewListener,
kRemoveListener,
kWeakHandler,
} = require('internal/event_target');
const {
customInspectSymbol,
kEnumerableProperty,
kEmptyObject,
createDeferredPromise,
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} = require('internal/util');
const { inspect } = require('internal/util/inspect');
const {
Expand Down Expand Up @@ -357,6 +360,20 @@ function transferableAbortController() {
return AbortController[kMakeTransferable]();
}

/**
* @param {AbortSignal} signal
* @param {any} resource
* @returns {Promise<void>}
*/
function aborted(signal, resource = null) {
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validateAbortSignal(signal, 'signal');
if (signal.aborted)
return PromiseResolve();
const abortPromise = createDeferredPromise();
signal.addEventListener('abort', abortPromise.resolve, { [kWeakHandler]: resource, once: true });
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return abortPromise.promise;
}

ObjectDefineProperties(AbortController.prototype, {
signal: kEnumerableProperty,
abort: kEnumerableProperty,
Expand All @@ -377,4 +394,5 @@ module.exports = {
ClonedAbortSignal,
transferableAbortSignal,
transferableAbortController,
aborted,
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};
3 changes: 3 additions & 0 deletions lib/util.js
Expand Up @@ -393,6 +393,9 @@ module.exports = {
get transferableAbortController() {
return lazyAbortController().transferableAbortController;
},
get aborted() {
return lazyAbortController().aborted;
},
types
};

Expand Down
37 changes: 37 additions & 0 deletions test/parallel/test-aborted-util.js
@@ -0,0 +1,37 @@
// Flags: --expose-gc
'use strict';

const common = require('../common');
const { aborted } = require('util');
const assert = require('assert');
const { getEventListeners } = require('events');

{
// Test aborted works
const ac = new AbortController();
aborted(ac.signal).then(common.mustCall());
ac.abort();
assert.strictEqual(ac.signal.aborted, true);
assert.strictEqual(getEventListeners(ac.signal, 'abort').length, 0);
}

{
// Test aborted works when provided a resource
const ac = new AbortController();
aborted(ac.signal, {}).then(common.mustCall());
ac.abort();
assert.strictEqual(ac.signal.aborted, true);
assert.strictEqual(getEventListeners(ac.signal, 'abort').length, 0);
}

{
// Test aborted with gc cleanup
const ac = new AbortController();
aborted(ac.signal, {}).then(common.mustNotCall());
setImmediate(() => {
global.gc();
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What does GC accomplish here? That the aborted() promise is collected before abort() is called?

I don't know if that kind of GC observability is a good thing. Maybe it works now but GC changes can break such patterns. Looks fragile.

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@debadree25 debadree25 Feb 4, 2023

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basically want to cleanup the empty object to check if the listener is removed when the resource is cleaned by the gc, unsure of any other ways to test this

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If it's just for testing, then it's probably fine. I mean, it could still break in the future but we can revisit if and when that happens.

I'd advise against documenting that behavior though. It's simply not very robust.

ac.abort();
assert.strictEqual(ac.signal.aborted, true);
assert.strictEqual(getEventListeners(ac.signal, 'abort').length, 0);
});
}