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events: support signal in EventTarget · nodejs/node@855a85c · GitHub

/ node Public

Commit 855a85c

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benjamingr
authored and
danielleadams
committed
events: support signal in EventTarget
PR-URL: #36258 Fixes: #36073 Reviewed-By: James M Snell <jasnell@gmail.com>
1 parent f317bba commit 855a85c

3 files changed

Lines changed: 186 additions & 0 deletions

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‎lib/internal/event_target.js‎

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Original file line numberDiff line numberDiff line change
@@ -200,10 +200,12 @@ class Listener {
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previous.next = this;
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this.previous = previous;
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this.listener = listener;
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// TODO(benjamingr) these 4 can be 'flags' to save 3 slots
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this.once = once;
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this.capture = capture;
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this.passive = passive;
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this.isNodeStyleListener = isNodeStyleListener;
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this.removed = false;
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208210
this.callback =
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typeof listener === 'function' ?
@@ -220,6 +222,7 @@ class Listener {
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this.previous.next = this.next;
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if (this.next !== undefined)
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this.next.previous = this.previous;
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this.removed = true;
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}
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}
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@@ -269,6 +272,7 @@ class EventTarget {
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once,
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capture,
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passive,
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signal,
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isNodeStyleListener
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} = validateEventListenerOptions(options);
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@@ -286,6 +290,17 @@ class EventTarget {
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}
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type = String(type);
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if (signal) {
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if (signal.aborted) {
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return false;
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}
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// TODO(benjamingr) make this weak somehow? ideally the signal would
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// not prevent the event target from GC.
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signal.addEventListener('abort', () => {
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this.removeEventListener(type, listener, options);
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}, { once: true });
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}
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let root = this[kEvents].get(type);
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291306
if (root === undefined) {
@@ -382,6 +397,12 @@ class EventTarget {
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// Cache the next item in case this iteration removes the current one
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next = handler.next;
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400+
if (handler.removed) {
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// Deal with the case an event is removed while event handlers are
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// Being processed (removeEventListener called from a listener)
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handler = next;
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continue;
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}
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if (handler.once) {
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handler.remove();
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root.size--;
@@ -550,6 +571,7 @@ function validateEventListenerOptions(options) {
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once: Boolean(options.once),
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capture: Boolean(options.capture),
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passive: Boolean(options.passive),
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signal: options.signal,
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isNodeStyleListener: Boolean(options[kIsNodeStyleListener])
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};
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}

‎test/parallel/test-eventtarget-whatwg-signal.js‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,155 @@
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'use strict';
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require('../common');
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const {
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strictEqual,
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} = require('assert');
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// Manually ported from: wpt@dom/events/AddEventListenerOptions-signal.any.js
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{
12+
// Passing an AbortSignal to addEventListener does not prevent
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// removeEventListener
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let count = 0;
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function handler() {
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count++;
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}
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const et = new EventTarget();
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const controller = new AbortController();
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et.addEventListener('test', handler, { signal: controller.signal });
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et.dispatchEvent(new Event('test'));
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strictEqual(count, 1, 'Adding a signal still adds a listener');
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et.dispatchEvent(new Event('test'));
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strictEqual(count, 2, 'The listener was not added with the once flag');
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controller.abort();
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et.dispatchEvent(new Event('test'));
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strictEqual(count, 2, 'Aborting on the controller removes the listener');
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et.addEventListener('test', handler, { signal: controller.signal });
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et.dispatchEvent(new Event('test'));
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strictEqual(count, 2, 'Passing an aborted signal never adds the handler');
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}
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{
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// Passing an AbortSignal to addEventListener works with the once flag
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let count = 0;
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function handler() {
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count++;
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}
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const et = new EventTarget();
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const controller = new AbortController();
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et.addEventListener('test', handler, { signal: controller.signal });
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et.removeEventListener('test', handler);
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et.dispatchEvent(new Event('test'));
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strictEqual(count, 0, 'The listener was still removed');
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}
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{
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// Removing a once listener works with a passed signal
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let count = 0;
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function handler() {
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count++;
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}
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const et = new EventTarget();
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const controller = new AbortController();
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const options = { signal: controller.signal, once: true };
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et.addEventListener('test', handler, options);
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controller.abort();
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et.dispatchEvent(new Event('test'));
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strictEqual(count, 0, 'The listener was still removed');
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}
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{
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let count = 0;
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function handler() {
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count++;
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}
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const et = new EventTarget();
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const controller = new AbortController();
69+
const options = { signal: controller.signal, once: true };
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et.addEventListener('test', handler, options);
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et.removeEventListener('test', handler);
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et.dispatchEvent(new Event('test'));
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strictEqual(count, 0, 'The listener was still removed');
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}
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{
77+
// Passing an AbortSignal to multiple listeners
78+
let count = 0;
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function handler() {
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count++;
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}
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const et = new EventTarget();
83+
const controller = new AbortController();
84+
const options = { signal: controller.signal, once: true };
85+
et.addEventListener('first', handler, options);
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et.addEventListener('second', handler, options);
87+
controller.abort();
88+
et.dispatchEvent(new Event('first'));
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et.dispatchEvent(new Event('second'));
90+
strictEqual(count, 0, 'The listener was still removed');
91+
}
92+
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{
94+
// Passing an AbortSignal to addEventListener works with the capture flag
95+
let count = 0;
96+
function handler() {
97+
count++;
98+
}
99+
const et = new EventTarget();
100+
const controller = new AbortController();
101+
const options = { signal: controller.signal, capture: true };
102+
et.addEventListener('test', handler, options);
103+
controller.abort();
104+
et.dispatchEvent(new Event('test'));
105+
strictEqual(count, 0, 'The listener was still removed');
106+
}
107+
108+
{
109+
// Aborting from a listener does not call future listeners
110+
let count = 0;
111+
function handler() {
112+
count++;
113+
}
114+
const et = new EventTarget();
115+
const controller = new AbortController();
116+
const options = { signal: controller.signal };
117+
et.addEventListener('test', () => {
118+
controller.abort();
119+
}, options);
120+
et.addEventListener('test', handler, options);
121+
et.dispatchEvent(new Event('test'));
122+
strictEqual(count, 0, 'The listener was still removed');
123+
}
124+
125+
{
126+
// Adding then aborting a listener in another listener does not call it
127+
let count = 0;
128+
function handler() {
129+
count++;
130+
}
131+
const et = new EventTarget();
132+
const controller = new AbortController();
133+
et.addEventListener('test', () => {
134+
et.addEventListener('test', handler, { signal: controller.signal });
135+
controller.abort();
136+
}, { signal: controller.signal });
137+
et.dispatchEvent(new Event('test'));
138+
strictEqual(count, 0, 'The listener was still removed');
139+
}
140+
141+
{
142+
// Aborting from a nested listener should remove it
143+
const et = new EventTarget();
144+
const ac = new AbortController();
145+
let count = 0;
146+
et.addEventListener('foo', () => {
147+
et.addEventListener('foo', () => {
148+
count++;
149+
if (count > 5) ac.abort();
150+
et.dispatchEvent(new Event('foo'));
151+
}, { signal: ac.signal });
152+
et.dispatchEvent(new Event('foo'));
153+
}, { once: true });
154+
et.dispatchEvent(new Event('foo'));
155+
}

‎test/parallel/test-eventtarget.js‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -532,3 +532,12 @@ let asyncTest = Promise.resolve();
532532
target.dispatchEvent(new Event('foo'));
533533
deepStrictEqual(output, [1, 2, 3, 4]);
534534
}
535+
{
536+
const et = new EventTarget();
537+
const listener = common.mustNotCall();
538+
et.addEventListener('foo', common.mustCall((e) => {
539+
et.removeEventListener('foo', listener);
540+
}));
541+
et.addEventListener('foo', listener);
542+
et.dispatchEvent(new Event('foo'));
543+
}

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