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events: make abort_controller event trusted #35811

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events: make abort_controller event trusted #35811

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5 changes: 3 additions & 2 deletions doc/api/events.md
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Expand Up @@ -1282,9 +1282,10 @@ This is not used in Node.js and is provided purely for completeness.
added: v14.5.0
-->

* Type: {boolean} Always returns `false`.
* Type: {boolean} True for Node.js internal events, false otherwise.

This is not used in Node.js and is provided purely for completeness.
Currently only `AbortSignal`s' `"abort"` event is fired with `isTrusted`
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set to `true`.

#### `event.preventDefault()`
<!-- YAML
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7 changes: 5 additions & 2 deletions lib/internal/abort_controller.js
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Expand Up @@ -11,7 +11,8 @@ const {

const {
EventTarget,
Event
Event,
kTrustEvent
} = require('internal/event_target');
const {
customInspectSymbol,
Expand Down Expand Up @@ -49,7 +50,9 @@ ObjectDefineProperties(AbortSignal.prototype, {
function abortSignal(signal) {
if (signal[kAborted]) return;
signal[kAborted] = true;
const event = new Event('abort');
const event = new Event('abort', {
[kTrustEvent]: true
});
if (typeof signal.onabort === 'function') {
signal.onabort(event);
}
Expand Down
15 changes: 14 additions & 1 deletion lib/internal/event_target.js
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Expand Up @@ -9,10 +9,12 @@ const {
ObjectAssign,
ObjectDefineProperties,
ObjectDefineProperty,
ObjectGetOwnPropertyDescriptor,
String,
Symbol,
SymbolFor,
SymbolToStringTag,
SafeWeakSet,
} = primordials;

const {
Expand Down Expand Up @@ -41,6 +43,7 @@ const kRemoveListener = Symbol('kRemoveListener');
const kIsNodeStyleListener = Symbol('kIsNodeStyleListener');
const kMaxListeners = Symbol('kMaxListeners');
const kMaxListenersWarned = Symbol('kMaxListenersWarned');
const kTrustEvent = Symbol('kTrustEvent');

// Lazy load perf_hooks to avoid the additional overhead on startup
let perf_hooks;
Expand All @@ -61,7 +64,12 @@ const kBubbles = Symbol('bubbles');
const kComposed = Symbol('composed');
const kPropagationStopped = Symbol('propagationStopped');

const isTrusted = () => false;
const isTrustedSet = new SafeWeakSet();
const isTrusted = ObjectGetOwnPropertyDescriptor({
get isTrusted() {
return isTrustedSet.has(this);
}
}, 'isTrusted').get;
Comment on lines +68 to +72
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Suggested change
const isTrusted = ObjectGetOwnPropertyDescriptor({
get isTrusted() {
return isTrustedSet.has(this);
}
}, 'isTrusted').get;
function isTrusted() {
return isTrustedSet.has(this);
}

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@ExE-Boss ExE-Boss Oct 26, 2020 •
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That will make the isTrusted getter function incorrectly have an own prototype property and the [[Construct]] internal method.

It will also cause it to have the wrong name.

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@ExE-Boss would you mind explaining why this doesn't work?

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@ExE-Boss ExE-Boss Oct 26, 2020 •
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Because the following will no longer throw a TypeError:

new (Object.getOwnPropertyDescriptor(new Event('foo'), "isTrusted").get)();

And the following will return "object" instead of "undefined":

typeof Object.getOwnPropertyDescriptor(new Event('foo'), "isTrusted").get.prototype;

And the following will return true instead of false:

Object.getOwnPropertyDescriptor(new Event('foo'), "isTrusted").get.hasOwnProperty("prototype");

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We should add a test for this across the EventTarget properties :]


class Event {
constructor(type, options) {
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To ensure that the Event constructor has the correct length, options should be initialised to null:

Suggested change
constructor(type, options) {
constructor(type, options = null) {

This also makes it possible to use strict equality comparison when checking options !== null.

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This sounds like a separate change from this one - @jasnell given past experience - would you prefer it if I made it here or if we opened an issue and it went on a separate PR?

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Either works I think. If you do it here make it a separate Commit but a separate pr also works

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Actually, I don't understand this - IIUC length is determined by the number of arguments - so Event.length should be 2 anyway.

I can add a test for that though - I'll push it in #35806

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Added in https://github.com/nodejs/node/pull/35806/files#diff-7177d219f295c5297f8e5d119cea177fc0b50c1df33161729ec0e1213f6c3b24R412

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@ExE-Boss ExE-Boss Oct 26, 2020 •
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@benjamingr

The length property defaults to the number of leading parameters without an initializer, and options = null makes the parameter have an initializer, thus the length will be 1:

https://tc39.es/ecma262/#sec-function-definitions-static-semantics-expectedargumentcount

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I fixed it in the other PR :]

Expand All @@ -77,6 +85,10 @@ class Event {
this[kDefaultPrevented] = false;
this[kTimestamp] = lazyNow();
this[kPropagationStopped] = false;
if (options != null && options[kTrustEvent]) {
isTrustedSet.add(this);
}

// isTrusted is special (LegacyUnforgeable)
ObjectDefineProperty(this, 'isTrusted', {
get: isTrusted,
Expand Down Expand Up @@ -571,5 +583,6 @@ module.exports = {
initNodeEventTarget,
kCreateEvent,
kNewListener,
kTrustEvent,
kRemoveListener,
};
4 changes: 4 additions & 0 deletions lib/internal/per_context/primordials.js
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Expand Up @@ -101,6 +101,10 @@ primordials.SafeSet = makeSafe(
Set,
class SafeSet extends Set {}
);
primordials.SafeWeakSet = makeSafe(
WeakSet,
class SafeWeakSet extends WeakSet {}
);
primordials.SafePromise = makeSafe(
Promise,
class SafePromise extends Promise {}
Expand Down
34 changes: 33 additions & 1 deletion test/parallel/test-abortcontroller.js
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@@ -1,11 +1,13 @@
// Flags: --no-warnings
// Flags: --no-warnings --expose-internals
'use strict';

const common = require('../common');

const { ok, strictEqual } = require('assert');
const { Event } = require('internal/event_target');
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@ExE-Boss ExE-Boss Oct 26, 2020 •
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This line is unnecessary, as the Event constructor is available as a global property.

Suggested change
const { Event } = require('internal/event_target');

It also causes the test to fail without the ‑‑expose‑internals flag.

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Event is currently not exposed globally as far as I know. Good catch on the flag - I'll add that.

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(Event is not exposed at all at the moment because as you can tell - there are still a bunch of rough edges we need to iron out - I intended to work on this a lot more a few months ago and am only getting to it now)

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@ExE-Boss ExE-Boss Oct 26, 2020 •
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Event is exposed since #35496, which shipped in v15.0.0:

node/lib/internal/bootstrap/node.js

Lines 143 to 148 in 9ff25b1

const {
EventTarget,
Event,
} = require('internal/event_target');
exposeInterface(global, 'EventTarget', EventTarget);
exposeInterface(global, 'Event', Event);

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/ping @benjamingr Good to make this change or not so much?

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I have no strong feelings regarding this - I didn't realize that we expose event globally and totally missed it.

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@ExE-Boss very cool I missed this!


{
// Tests that abort is fired with the correct event type on AbortControllers
const ac = new AbortController();
ok(ac.signal);
ac.signal.onabort = common.mustCall((event) => {
Expand All @@ -20,3 +22,33 @@ const { ok, strictEqual } = require('assert');
ac.abort();
ok(ac.signal.aborted);
}

{
// Tests that abort events are trusted
const ac = new AbortController();
ac.signal.addEventListener('abort', common.mustCall((event) => {
ok(event.isTrusted);
}));
ac.abort();
}

{
// Tests that abort events have the same `isTrusted` reference
const first = new AbortController();
const second = new AbortController();
let ev1, ev2;
const ev3 = new Event('abort');
first.signal.addEventListener('abort', common.mustCall((event) => {
ev1 = event;
}));
second.signal.addEventListener('abort', common.mustCall((event) => {
ev2 = event;
}));
first.abort();
second.abort();
const firstTrusted = Reflect.getOwnPropertyDescriptor(ev1, 'isTrusted').get;
const secondTrusted = Reflect.getOwnPropertyDescriptor(ev2, 'isTrusted').get;
const untrusted = Reflect.getOwnPropertyDescriptor(ev3, 'isTrusted').get;
strictEqual(firstTrusted, secondTrusted);
strictEqual(untrusted, firstTrusted);
}