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events.js
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1218 lines (1074 loc) · 34.6 KB
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// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.
'use strict';
const {
ArrayPrototypeJoin,
ArrayPrototypePop,
ArrayPrototypePush,
ArrayPrototypeSlice,
ArrayPrototypeSplice,
ArrayPrototypeUnshift,
AsyncIteratorPrototype,
Boolean,
Error,
ErrorCaptureStackTrace,
FunctionPrototypeBind,
NumberMAX_SAFE_INTEGER,
ObjectDefineProperties,
ObjectDefineProperty,
ObjectGetPrototypeOf,
ObjectSetPrototypeOf,
Promise,
PromiseReject,
PromiseResolve,
ReflectApply,
ReflectOwnKeys,
String,
StringPrototypeSplit,
Symbol,
SymbolAsyncIterator,
SymbolDispose,
SymbolFor,
} = primordials;
const kRejection = SymbolFor('nodejs.rejection');
const { kEmptyObject, spliceOne } = require('internal/util');
const {
inspect,
identicalSequenceRange,
} = require('internal/util/inspect');
let FixedQueue;
let kFirstEventParam;
let kResistStopPropagation;
const {
AbortError,
codes: {
ERR_INVALID_ARG_TYPE,
ERR_UNHANDLED_ERROR,
},
genericNodeError,
kEnhanceStackBeforeInspector,
} = require('internal/errors');
const {
validateInteger,
validateAbortSignal,
validateBoolean,
validateFunction,
validateNumber,
validateObject,
validateString,
} = require('internal/validators');
const { addAbortListener } = require('internal/events/abort_listener');
const kCapture = Symbol('kCapture');
const kErrorMonitor = Symbol('events.errorMonitor');
const kShapeMode = Symbol('shapeMode');
const kMaxEventTargetListeners = Symbol('events.maxEventTargetListeners');
const kMaxEventTargetListenersWarned =
Symbol('events.maxEventTargetListenersWarned');
const kWatermarkData = SymbolFor('nodejs.watermarkData');
let EventEmitterAsyncResource;
// The EventEmitterAsyncResource has to be initialized lazily because event.js
// is loaded so early in the bootstrap process, before async_hooks is available.
//
// This implementation was adapted straight from addaleax's
// eventemitter-asyncresource MIT-licensed userland module.
// https://github.com/addaleax/eventemitter-asyncresource
function lazyEventEmitterAsyncResource() {
if (EventEmitterAsyncResource === undefined) {
const {
AsyncResource,
} = require('async_hooks');
class EventEmitterReferencingAsyncResource extends AsyncResource {
#eventEmitter;
/**
* @param {EventEmitter} ee
* @param {string} [type]
* @param {{
* triggerAsyncId?: number,
* requireManualDestroy?: boolean,
* }} [options]
*/
constructor(ee, type, options) {
super(type, options);
this.#eventEmitter = ee;
}
/**
* @type {EventEmitter}
*/
get eventEmitter() {
return this.#eventEmitter;
}
}
EventEmitterAsyncResource =
class EventEmitterAsyncResource extends EventEmitter {
#asyncResource;
/**
* @param {{
* name?: string,
* triggerAsyncId?: number,
* requireManualDestroy?: boolean,
* }} [options]
*/
constructor(options = undefined) {
let name;
if (typeof options === 'string') {
name = options;
options = undefined;
} else {
if (new.target === EventEmitterAsyncResource) {
validateString(options?.name, 'options.name');
}
name = options?.name || new.target.name;
}
super(options);
this.#asyncResource = new EventEmitterReferencingAsyncResource(this, name, options);
}
/**
* @param {symbol|string} event
* @param {any[]} args
* @returns {boolean}
*/
emit(event, ...args) {
const asyncResource = this.#asyncResource;
ArrayPrototypeUnshift(args, super.emit, this, event);
return ReflectApply(asyncResource.runInAsyncScope, asyncResource,
args);
}
/**
* @returns {void}
*/
emitDestroy() {
this.#asyncResource.emitDestroy();
}
/**
* @type {number}
*/
get asyncId() {
return this.#asyncResource.asyncId();
}
/**
* @type {number}
*/
get triggerAsyncId() {
return this.#asyncResource.triggerAsyncId();
}
/**
* @type {EventEmitterReferencingAsyncResource}
*/
get asyncResource() {
return this.#asyncResource;
}
};
}
return EventEmitterAsyncResource;
}
/**
* Creates a new `EventEmitter` instance.
* @param {{ captureRejections?: boolean; }} [opts]
* @constructs EventEmitter
*/
function EventEmitter(opts) {
EventEmitter.init.call(this, opts);
}
module.exports = EventEmitter;
module.exports.addAbortListener = addAbortListener;
module.exports.once = once;
module.exports.on = on;
module.exports.getEventListeners = getEventListeners;
module.exports.getMaxListeners = getMaxListeners;
module.exports.listenerCount = listenerCount;
// Backwards-compat with node 0.10.x
EventEmitter.EventEmitter = EventEmitter;
EventEmitter.usingDomains = false;
EventEmitter.captureRejectionSymbol = kRejection;
ObjectDefineProperty(EventEmitter, 'captureRejections', {
__proto__: null,
get() {
return EventEmitter.prototype[kCapture];
},
set(value) {
validateBoolean(value, 'EventEmitter.captureRejections');
EventEmitter.prototype[kCapture] = value;
},
enumerable: true,
});
ObjectDefineProperty(EventEmitter, 'EventEmitterAsyncResource', {
__proto__: null,
enumerable: true,
get: lazyEventEmitterAsyncResource,
set: undefined,
configurable: true,
});
EventEmitter.errorMonitor = kErrorMonitor;
// The default for captureRejections is false
ObjectDefineProperty(EventEmitter.prototype, kCapture, {
__proto__: null,
value: false,
writable: true,
enumerable: false,
});
EventEmitter.prototype._events = undefined;
EventEmitter.prototype._eventsCount = 0;
EventEmitter.prototype._maxListeners = undefined;
// By default EventEmitters will print a warning if more than 10 listeners are
// added to it. This is a useful default which helps finding memory leaks.
let defaultMaxListeners = 10;
let isEventTarget;
function checkListener(listener) {
validateFunction(listener, 'listener');
}
ObjectDefineProperty(EventEmitter, 'defaultMaxListeners', {
__proto__: null,
enumerable: true,
get: function() {
return defaultMaxListeners;
},
set: function(arg) {
validateNumber(arg, 'defaultMaxListeners', 0);
defaultMaxListeners = arg;
},
});
ObjectDefineProperties(EventEmitter, {
kMaxEventTargetListeners: {
__proto__: null,
value: kMaxEventTargetListeners,
enumerable: false,
configurable: false,
writable: false,
},
kMaxEventTargetListenersWarned: {
__proto__: null,
value: kMaxEventTargetListenersWarned,
enumerable: false,
configurable: false,
writable: false,
},
});
/**
* Sets the max listeners.
* @param {number} n
* @param {EventTarget[] | EventEmitter[]} [eventTargets]
* @returns {void}
*/
EventEmitter.setMaxListeners =
function(n = defaultMaxListeners, ...eventTargets) {
validateNumber(n, 'setMaxListeners', 0);
if (eventTargets.length === 0) {
defaultMaxListeners = n;
} else {
if (isEventTarget === undefined)
isEventTarget = require('internal/event_target').isEventTarget;
for (let i = 0; i < eventTargets.length; i++) {
const target = eventTargets[i];
if (isEventTarget(target)) {
target[kMaxEventTargetListeners] = n;
target[kMaxEventTargetListenersWarned] = false;
} else if (typeof target.setMaxListeners === 'function') {
target.setMaxListeners(n);
} else {
throw new ERR_INVALID_ARG_TYPE(
CE9B
'eventTargets',
['EventEmitter', 'EventTarget'],
target);
}
}
}
};
// If you're updating this function definition, please also update any
// re-definitions, such as the one in the Domain module (lib/domain.js).
EventEmitter.init = function(opts) {
if (this._events === undefined ||
this._events === ObjectGetPrototypeOf(this)._events) {
this._events = { __proto__: null };
this._eventsCount = 0;
this[kShapeMode] = false;
} else {
this[kShapeMode] = true;
}
this._maxListeners ||= undefined;
if (opts?.captureRejections) {
validateBoolean(opts.captureRejections, 'options.captureRejections');
this[kCapture] = Boolean(opts.captureRejections);
} else {
// Assigning the kCapture property directly saves an expensive
// prototype lookup in a very sensitive hot path.
this[kCapture] = EventEmitter.prototype[kCapture];
}
};
function addCatch(that, promise, type, args) {
if (!that[kCapture]) {
return;
}
// Handle Promises/A+ spec, then could be a getter
// that throws on second use.
try {
const then = promise.then;
if (typeof then === 'function') {
then.call(promise, undefined, function(err) {
// The callback is called with nextTick to avoid a follow-up
// rejection from this promise.
process.nextTick(emitUnhandledRejectionOrErr, that, err, type, args);
});
}
} catch (err) {
that.emit('error', err);
}
}
function emitUnhandledRejectionOrErr(ee, err, type, args) {
if (typeof ee[kRejection] === 'function') {
ee[kRejection](err, type, ...args);
} else {
// We have to disable the capture rejections mechanism, otherwise
// we might end up in an infinite loop.
const prev = ee[kCapture];
// If the error handler throws, it is not catchable and it
// will end up in 'uncaughtException'. We restore the previous
// value of kCapture in case the uncaughtException is present
// and the exception is handled.
try {
ee[kCapture] = false;
ee.emit('error', err);
} finally {
ee[kCapture] = prev;
}
}
}
/**
* Increases the max listeners of the event emitter.
* @param {number} n
* @returns {EventEmitter}
*/
EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
validateNumber(n, 'setMaxListeners', 0);
this._maxListeners = n;
return this;
};
function _getMaxListeners(that) {
if (that._maxListeners === undefined)
return EventEmitter.defaultMaxListeners;
return that._maxListeners;
}
/**
* Returns the current max listener value for the event emitter.
* @returns {number}
*/
EventEmitter.prototype.getMaxListeners = function getMaxListeners() {
return _getMaxListeners(this);
};
function enhanceStackTrace(err, own) {
let ctorInfo = '';
try {
const { name } = this.constructor;
if (name !== 'EventEmitter')
ctorInfo = ` on ${name} instance`;
} catch {
// Continue regardless of error.
}
const sep = `\nEmitted 'error' event${ctorInfo} at:\n`;
const errStack = ArrayPrototypeSlice(
StringPrototypeSplit(err.stack, '\n'), 1);
const ownStack = ArrayPrototypeSlice(
StringPrototypeSplit(own.stack, '\n'), 1);
const { len, offset } = identicalSequenceRange(ownStack, errStack);
if (len > 0) {
ArrayPrototypeSplice(ownStack, offset + 1, len - 2,
' [... lines matching original stack trace ...]');
}
return err.stack + sep + ArrayPrototypeJoin(ownStack, '\n');
}
/**
* Synchronously calls each of the listeners registered
* for the event.
* @param {string | symbol} type
* @param {...any} [args]
* @returns {boolean}
*/
EventEmitter.prototype.emit = function emit(type, ...args) {
let doError = (type === 'error');
const events = this._events;
if (events !== undefined) {
if (doError && events[kErrorMonitor] !== undefined)
this.emit(kErrorMonitor, ...args);
doError &&= events.error === undefined;
} else if (!doError)
return false;
// If there is no 'error' event listener then throw.
if (doError) {
let er;
if (args.length > 0)
er = args[0];
if (er instanceof Error) {
try {
const capture = {};
ErrorCaptureStackTrace(capture, EventEmitter.prototype.emit);
ObjectDefineProperty(er, kEnhanceStackBeforeInspector, {
__proto__: null,
value: FunctionPrototypeBind(enhanceStackTrace, this, er, capture),
configurable: true,
});
} catch {
// Continue regardless of error.
}
// Note: The comments on the `throw` lines are intentional, they show
// up in Node's output if this results in an unhandled exception.
throw er; // Unhandled 'error' event
}
let stringifiedEr;
try {
stringifiedEr = inspect(er);
} catch {
stringifiedEr = er;
}
// At least give some kind of context to the user
const err = new ERR_UNHANDLED_ERROR(stringifiedEr);
err.context = er;
throw err; // Unhandled 'error' event
}
const handler = events[type];
if (handler === undefined)
return false;
if (typeof handler === 'function') {
const result = ReflectApply(handler, this, args);
// We check if result is undefined first because that
// is the most common case so we do not pay any perf
// penalty
if (result !== undefined && result !== null) {
addCatch(this, result, type, args);
}
} else {
const len = handler.length;
const listeners = arrayClone(handler);
for (let i = 0; i < len; ++i) {
const result = ReflectApply(listeners[i], this, args);
// We check if result is undefined first because that
// is the most common case so we do not pay any perf
// penalty.
// This code is duplicated because extracting it away
// would make it non-inlineable.
if (result !== undefined && result !== null) {
addCatch(this, result, type, args);
}
}
}
return true;
};
function _addListener(target, type, listener, prepend) {
let m;
let events;
let existing;
checkListener(listener);
events = target._events;
if (events === undefined) {
events = target._events = { __proto__: null };
target._eventsCount = 0;
} else {
// To avoid recursion in the case that type === "newListener"! Before
// adding it to the listeners, first emit "newListener".
if (events.newListener !== undefined) {
target.emit('newListener', type,
listener.listener ?? listener);
// Re-assign `events` because a newListener handler could have caused the
// this._events to be assigned to a new object
events = target._events;
}
existing = events[type];
}
if (existing === undefined) {
// Optimize the case of one listener. Don't need the extra array object.
events[type] = listener;
++target._eventsCount;
} else {
if (typeof existing === 'function') {
// Adding the second element, need to change to array.
existing = events[type] =
prepend ? [listener, existing] : [existing, listener];
// If we've already got an array, just append.
} else if (prepend) {
existing.unshift(listener);
} else {
existing.push(listener);
}
// Check for listener leak
m = _getMaxListeners(target);
if (m > 0 && existing.length > m && !existing.warned) {
existing.warned = true;
// No error code for this since it is a Warning
const w = genericNodeError(
`Possible EventEmitter memory leak detected. ${existing.length} ${String(type)} listeners ` +
`added to ${inspect(target, { depth: -1 })}. MaxListeners is ${m}. Use emitter.setMaxListeners() to increase limit`,
{ name: 'MaxListenersExceededWarning', emitter: target, type: type, count: existing.length });
process.emitWarning(w);
}
}
return target;
}
/**
* Adds a listener to the event emitter.
* @param {string | symbol} type
* @param {Function} listener
* @returns {EventEmitter}
*/
EventEmitter.prototype.addListener = function addListener(type, listener) {
return _addListener(this, type, listener, false);
};
EventEmitter.prototype.on = EventEmitter.prototype.addListener;
/**
* Adds the `listener` function to the beginning of
* the listeners array.
* @param {string | symbol} type
* @param {Function} listener
* @returns {EventEmitter}
*/
EventEmitter.prototype.prependListener =
function prependListener(type, listener) {
return _addListener(this, type, listener, true);
};
function onceWrapper() {
if (!this.fired) {
this.target.removeListener(this.type, this.wrapFn);
this.fired = true;
if (arguments.length === 0)
return this.listener.call(this.target);
return ReflectApply(this.listener, this.target, arguments);
}
}
function _onceWrap(target, type, listener) {
const state = { fired: false, wrapFn: undefined, target, type, listener };
const wrapped = onceWrapper.bind(state);
wrapped.listener = listener;
state.wrapFn = wrapped;
return wrapped;
}
/**
* Adds a one-time `listener` function to the event emitter.
* @param {string | symbol} type
* @param {Function} listener
* @returns {EventEmitter}
*/
EventEmitter.prototype.once = function once(type, listener) {
checkListener(listener);
this.on(type, _onceWrap(this, type, listener));
return this;
};
/**
* Adds a one-time `listener` function to the beginning of
* the listeners array.
* @param {string | symbol} type
* @param {Function} listener
* @returns {EventEmitter}
*/
EventEmitter.prototype.prependOnceListener =
function prependOnceListener(type, listener) {
checkListener(listener);
this.prependListener(type, _onceWrap(this, type, listener));
return this;
};
/**
* Removes the specified `listener` from the listeners array.
* @param {string | symbol} type
* @param {Function} listener
* @returns {EventEmitter}
*/
EventEmitter.prototype.removeListener =
function removeListener(type, listener) {
checkListener(listener);
const events = this._events;
if (events === undefined)
return this;
const list = events[type];
if (list === undefined)
return this;
if (list === listener || list.listener === listener) {
this._eventsCount -= 1;
if (this[kShapeMode]) {
events[type] = undefined;
} else if (this._eventsCount === 0) {
this._events = { __proto__: null };
} else {
delete events[type];
}
if (events.removeListener !== undefined)
this.emit('removeListener', type, list.listener || listener);
} else if (typeof list !== 'function') {
let position = -1;
for (let i = list.length - 1; i >= 0; i--) {
if (list[i] === listener || list[i].listener === listener) {
position = i;
break;
}
}
if (position < 0)
return this;
if (position === 0)
list.shift();
else {
spliceOne(list, position);
}
if (list.length === 1)
events[type] = list[0];
if (events.removeListener !== undefined)
this.emit('removeListener', type, listener);
}
return this;
};
EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
/**
* Removes all listeners from the event emitter. (Only
* removes listeners for a specific event name if specified
* as `type`).
* @param {string | symbol} [type]
* @returns {EventEmitter}
*/
EventEmitter.prototype.removeAllListeners =
function removeAllListeners(type) {
const events = this._events;
if (events === undefined)
return this;
// Not listening for removeListener, no need to emit
if (events.removeListener === undefined) {
if (arguments.length === 0) {
this._events = { __proto__: null };
this._eventsCount = 0;
} else if (events[type] !== undefined) {
if (--this._eventsCount === 0)
this._events = { __proto__: null };
else
delete events[type];
}
this[kShapeMode] = false;
return this;
}
// Emit removeListener for all listeners on all events
if (arguments.length === 0) {
for (const key of ReflectOwnKeys(events)) {
if (key === 'removeListener') continue;
this.removeAllListeners(key);
}
this.removeAllListeners('removeListener');
this._events = { __proto__: null };
this._eventsCount = 0;
this[kShapeMode] = false;
return this;
}
const listeners = events[type];
if (typeof listeners === 'function') {
this.removeListener(type, listeners);
} else if (listeners !== undefined) {
// LIFO order
for (let i = listeners.length - 1; i >= 0; i--) {
this.removeListener(type, listeners[i]);
}
}
return this;
};
function _listeners(target, type, unwrap) {
const events = target._events;
if (events === undefined)
return [];
const evlistener = events[type];
if (evlistener === undefined)
return [];
if (typeof evlistener === 'function')
return unwrap ? [evlistener.listener || evlistener] : [evlistener];
return unwrap ?
unwrapListeners(evlistener) : arrayClone(evlistener);
}
/**
* Returns a copy of the array of listeners for the event name
* specified as `type`.
* @param {string | symbol} type
* @returns {Function[]}
*/
EventEmitter.prototype.listeners = function listeners(type) {
3D25
return _listeners(this, type, true);
};
/**
* Returns a copy of the array of listeners and wrappers for
* the event name specified as `type`.
* @param {string | symbol} type
* @returns {Function[]}
*/
EventEmitter.prototype.rawListeners = function rawListeners(type) {
return _listeners(this, type, false);
};
/**
* Returns the number of listeners listening to event name
* specified as `type`.
* @param {string | symbol} type
* @param {Function} [listener]
* @returns {number}
*/
EventEmitter.prototype.listenerCount = function listenerCount(type, listener) {
const events = this._events;
if (events !== undefined) {
const evlistener = events[type];
if (typeof evlistener === 'function') {
if (listener != null) {
return listener === evlistener || listener === evlistener.listener ? 1 : 0;
}
return 1;
} else if (evlistener !== undefined) {
if (listener != null) {
let matching = 0;
for (let i = 0, l = evlistener.length; i < l; i++) {
if (evlistener[i] === listener || evlistener[i].listener === listener) {
matching++;
}
}
return matching;
}
return evlistener.length;
}
}
return 0;
};
/**
* Returns an array listing the events for which
* the emitter has registered listeners.
* @returns {(string | symbol)[]}
*/
EventEmitter.prototype.eventNames = function eventNames() {
return this._eventsCount > 0 ? ReflectOwnKeys(this._events) : [];
};
function arrayClone(arr) {
// At least since V8 8.3, this implementation is faster than the previous
// which always used a sim
B57A
ple for-loop
switch (arr.length) {
case 2: return [arr[0], arr[1]];
case 3: return [arr[0], arr[1], arr[2]];
case 4: return [arr[0], arr[1], arr[2], arr[3]];
case 5: return [arr[0], arr[1], arr[2], arr[3], arr[4]];
case 6: return [arr[0], arr[1], arr[2], arr[3], arr[4], arr[5]];
}
return ArrayPrototypeSlice(arr);
}
function unwrapListeners(arr) {
const ret = arrayClone(arr);
for (let i = 0; i < ret.length; ++i) {
const orig = ret[i].listener;
if (typeof orig === 'function')
ret[i] = orig;
}
return ret;
}
/**
* Returns a copy of the array of listeners for the event name
* specified as `type`.
* @param {EventEmitter | EventTarget} emitterOrTarget
* @param {string | symbol} type
* @returns {Function[]}
*/
function getEventListeners(emitterOrTarget, type) {
// First check if EventEmitter
if (typeof emitterOrTarget.listeners === 'function') {
return emitterOrTarget.listeners(type);
}
// Require event target lazily to avoid always loading it
const { isEventTarget, kEvents } = require('internal/event_target');
if (isEventTarget(emitterOrTarget)) {
const root = emitterOrTarget[kEvents].get(type);
const listeners = [];
let handler = root?.next;
while (handler?.listener !== undefined) {
const listener = handler.listener?.deref ?
handler.listener.deref() : handler.listener;
listeners.push(listener);
handler = handler.next;
}
return listeners;
}
throw new ERR_INVALID_ARG_TYPE('emitter',
['EventEmitter', 'EventTarget'],
emitterOrTarget);
}
/**
* Returns the max listeners set.
* @param {EventEmitter | EventTarget} emitterOrTarget
* @returns {number}
*/
function getMaxListeners(emitterOrTarget) {
if (typeof emitterOrTarget?.getMaxListeners === 'function') {
return _getMaxListeners(emitterOrTarget);
} else if (typeof emitterOrTarget?.[kMaxEventTargetListeners] === 'number') {
return emitterOrTarget[kMaxEventTargetListeners];
}
throw new ERR_INVALID_ARG_TYPE('emitter',
['EventEmitter', 'EventTarget'],
emitterOrTarget);
}
/**
* Returns the number of registered listeners for `type`.
* @param {EventEmitter | EventTarget} emitterOrTarget
* @param {string | symbol} type
* @returns {number}
*/
function listenerCount(emitterOrTarget, type) {
if (typeof emitterOrTarget.listenerCount === 'function') {
return emitterOrTarget.listenerCount(type);
}
const { isEventTarget, kEvents } = require('internal/event_target');
if (isEventTarget(emitterOrTarget)) {
return emitterOrTarget[kEvents].get(type)?.size ?? 0;
}
throw new ERR_INVALID_ARG_TYPE('emitter',
['EventEmitter', 'EventTarget'],
emitterOrTarget);
}
/**
* Creates a `Promise` that is fulfilled when the emitter
* emits the given event.
* @param {EventEmitter} emitter
* @param {string | symbol} name
* @param {{ signal: AbortSignal; }} [options]
* @returns {Promise}
*/
async function once(emitter, name, options = kEmptyObject) {
validateObject(options, 'options');
const { signal } = options;
validateAbortSignal(signal, 'options.signal');
if (signal?.aborted)
throw new AbortError(undefined, { cause: signal.reason });
return new Promise((resolve, reject) => {
const errorListener = (err) => {
emitter.removeListener(name, resolver);
if (signal != null) {
eventTargetAgnosticRemoveListener(signal, 'abort', abortListener);
}
reject(err);
};
const resolver = (...args) => {
if (typeof emitter.removeListener === 'function') {
emitter.removeListener('error', errorListener);
}
if (signal != null) {
eventTargetAgnosticRemoveListener(signal, 'abort', abortListener);
}
resolve(args);
};
kResistStopPropagation ??= require('internal/event_target').kResistStopPropagation;
const opts = { __proto__: null, once: true, [kResistStopPropagation]: true };
eventTargetAgnosticAddListener(emitter, name, resolver, opts);
if (name !== 'error' && typeof emitter.once === 'function') {
// EventTarget does not have `error` event semantics like Node
// EventEmitters, we listen to `error` events only on EventEmitters.
emitter.once('error', errorListener);
}
function abortListener() {
eventTargetAgnosticRemoveListener(emitter, name, resolver);
eventTargetAgnosticRemoveListener(emitter, 'error', errorListener);
reject(new AbortError(undefined, { cause: signal?.reason }));
}
if (signal != null) {