Merge branch 'event-emitter' into 'development'

Add Event Emitter

See merge request GeneralProtocols/xo/utils!13
This commit is contained in:
Kuldeep
2026-08-12 18:48:51 +00:00
8 changed files with 1144 additions and 7 deletions
+1 -1
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@@ -1,6 +1,6 @@
{
"version": "0.1",
"import": ["@generalprotocols/cspell-dictionary/cspell.json"],
"words": ["nonfungible", "lockscript", "cashassembly", "checksigverify", "inputindex", "utxovalue"],
"words": ["nonfungible", "lockscript", "cashassembly", "checksigverify", "inputindex", "utxovalue", "bivariance"],
"ignorePaths": ["source/template/xo-template.schema.json"]
}
+6 -6
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@@ -7034,9 +7034,9 @@
"license": "MIT"
},
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"version": "4.3.0",
"resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.3.0.tgz",
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"version": "4.3.1",
"resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.3.1.tgz",
"integrity": "sha512-CY6crGq313MX8GkwvB7tzgp99vjQxY1++5y10/BKN/GUfHqWaOGQMNZkBvqSzsZKWk/ijwHlWzzkLulsGHhjWQ==",
"dev": true,
"funding": [
{
@@ -7715,9 +7715,9 @@
"license": "MIT"
},
"node_modules/nanoid": {
"version": "3.3.16",
"resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.16.tgz",
"integrity": "sha512-bzlKTyNJ7+LdGIIwy8ijFpIqEQIvafahV7eYykJ8Cvh42EdJeODoJ6gUJXpQJvej1BddH8OqTXZNE/KfbWAu8Q==",
"version": "3.3.18",
"resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.18.tgz",
"integrity": "sha512-DTg4MJbGMWkfi6VZFdNt2/caMbQy4Ou+Op/hJQvGEWcnVfoA1QA+xzRKAzw9jD6+GVOOeYr/mIcuDSdug6F6+w==",
"dev": true,
"funding": [
{
+9
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@@ -0,0 +1,9 @@
/**
* Error thrown when a waitFor timeout is reached
*/
export class WaitForTimeoutError extends Error {
constructor(type: string) {
super(`Timeout waiting for event "${type}"`);
this.name = 'WaitForTimeoutError';
}
}
+278
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@@ -0,0 +1,278 @@
import type { DeeplyReadonly } from './types.ts';
import type { deepFreeze } from './misc.ts';
import { WaitForTimeoutError } from './errors.ts';
export type EventMap = Record<string, unknown>;
type Listener<T> = (detail: T) => void;
/**
* Internally permits listeners for individual event payloads to be stored
* in a collection typed with the union of all event payloads.
*/
type StoredListener<T> = {
bivarianceHack(detail: T): void;
}['bivarianceHack'];
/**
* A listener entry.
* @template T - The event payload type.
*/
interface ListenerEntry<T> {
listener: StoredListener<T>;
wrappedListener: StoredListener<T>;
cancel: () => void;
}
/**
* Callback returned by {@link on} and {@link once} for removing a listener.
*/
export type OffCallback = () => void;
/**
* A simple event emitter implementation.
* @template T - The event map type.
*/
export class EventEmitter<T extends EventMap> {
/**
* The listeners map.
* @private
*/
#listeners: Map<keyof T, Set<ListenerEntry<T[keyof T]>>> = new Map();
/**
* Add a listener for an event.
* @param type - The event type.
* @param listener - The listener function.
* @param debounceMilliseconds - The debounce time in milliseconds.
* @returns An off callback that can be called to stop listening for events.
*/
on<K extends keyof T>(type: K, listener: Listener<T[K]>, debounceMilliseconds: number = 0): OffCallback {
const { cancel, listener: cancellableListener } = this.cancellable(listener);
// Create a wrapped listener so that the debounce can be applied.
const wrappedListener = debounceMilliseconds > 0 ? this.debounce(cancellableListener, debounceMilliseconds) : cancellableListener;
// If the listeners map does not have the event type, create a new set.
if (!this.#listeners.has(type)) {
this.#listeners.set(type, new Set());
}
// Create a listener entry.
const listenerEntry: ListenerEntry<T[K]> = {
listener,
wrappedListener,
cancel,
};
// Add the listener entry to the listeners map.
this.#listeners.get(type)?.add(listenerEntry);
// Return an "off" callback that can be called to stop listening for events.
return () => this.off(type, listener);
}
/**
* Add a one-time listener for an event.
* @param type - The event type.
* @param listener - The listener function.
* @param debounceMilliseconds - The debounce time in milliseconds.
* @returns An off callback that can be called to stop listening for events.
*/
once<K extends keyof T>(type: K, listener: Listener<T[K]>, debounceMilliseconds: number = 0): OffCallback {
const wrappedListener: Listener<T[K]> = (detail: T[K]) => {
this.off(type, listener);
listener(detail);
};
// Create a cancellable listener.
const { cancel, listener: cancellableListener } = this.cancellable(wrappedListener);
// Create a debounced listener.
const debouncedListener = debounceMilliseconds > 0 ? this.debounce(cancellableListener, debounceMilliseconds) : cancellableListener;
// If the listeners map does not have the event type, create a new set.
if (!this.#listeners.has(type)) {
this.#listeners.set(type, new Set());
}
// Create a listener entry.
const listenerEntry: ListenerEntry<T[K]> = {
listener,
wrappedListener: debouncedListener,
cancel,
};
// Add the listener entry to the listeners map.
this.#listeners.get(type)?.add(listenerEntry);
// Return an "off" callback that can be called to stop listening for events.
return () => this.off(type, listener);
}
/**
* Remove a listener for an event.
* @param type - The event type.
* @param listener - The listener function.
*/
off<K extends keyof T>(type: K, listener?: Listener<T[K]>): void {
// Get the listeners for the event type.
const listeners = this.#listeners.get(type);
if (!listeners) return;
// Find the listener entries (If a listener was provided, only 1 entry will be returned. Otherwise, all entries will be returned).
const listenerEntries = Array.from(listeners).filter((entry) => !listener || entry.listener === listener || entry.wrappedListener === listener);
// Remove the listener entries from the listeners set.
listenerEntries.forEach((entry) => {
// Set the wrapped listener to a no-op function to prevent it from being called by debounced events after it's been removed.
entry.cancel();
// Remove the listener entry from the listeners set.
listeners.delete(entry);
});
// If no listener was provided and no listeners are left for the event type, remove the listeners set from the listeners map.
if (!listener || this.#listeners.get(type)?.size === 0) {
this.#listeners.delete(type);
}
}
/**
* Emit an event.
*
* @remarks The caller is responsible for ensuring the payload suits the intended mutability requirements.
* By default, the payload will be mutable, so listeners may mutate the payload, effecting both
* the original object and the other listeners.
* To prevent this, the caller can use the {@link Object.freeze} or {@link deepFreeze} function to freeze the payload.
* This will need to be defined in the EventMap using the built-in {@link Readonly} type or the provided {@link DeeplyReadonly} type.
*
* @param type - The event type.
* @param payload - The event payload.
* @returns True if there are listeners for the event, false otherwise.
*/
emit<K extends keyof T>(type: K, payload: T[K]): boolean {
// Get the listeners for the event type.
const listeners = this.#listeners.get(type);
if (!listeners) return false;
// Emit the event to all listeners.
listeners.forEach((entry) => {
try {
entry.wrappedListener(payload);
} catch (error) {
console.error(error);
}
});
// Return true if there are listeners for the event, false otherwise.
return listeners.size > 0;
}
/**
* Remove all listeners.
*/
removeAllListeners(): void {
for (const [ type, listeners ] of this.#listeners.entries()) {
listeners.forEach((entry) => {
this.off(type, entry.listener);
});
}
}
/**
* Wait for an event to be emitted that matches the provided predicate function's criteria.
* @param type - The event type.
* @param predicate - Predicate function to filter for whether the event payload matches the criteria.
* @param timeoutMs - The timeout in milliseconds.
* @returns The event payload.
*/
async waitFor<K extends keyof T>(type: K, predicate: (payload: T[K]) => boolean, timeoutMs?: number): Promise<T[K]> {
// Create a promise to wait for the event to be emitted.
return new Promise((resolve, reject) => {
let timeoutId: ReturnType<typeof setTimeout> | undefined;
// Create a cleanup function to remove the listener and clear the timeout if it is still pending.
const cleanup = (listener: Listener<T[K]>): void => {
// Remove the listener from the listeners map.
this.off(type, listener);
// Clear the timeout if it is still pending.
if (timeoutId !== undefined) {
clearTimeout(timeoutId);
}
};
// Create a listener function.
const listener = (payload: T[K]): void => {
try {
// If the event payload does not match the predicate condition, return.
if (!predicate(payload)) {
return;
}
cleanup(listener);
resolve(payload);
} catch (error) {
cleanup(listener);
reject(error);
}
};
// Set up timeout if specified
if (timeoutMs !== undefined) {
timeoutId = setTimeout(() => {
this.off(type, listener);
reject(new WaitForTimeoutError(String(type)));
}, timeoutMs);
}
// Add the listener to the listeners map.
this.on(type, listener);
});
}
/**
* Debounce a function.
*
* @remarks If {@link off} is called on a listener while it is debounced, the timeout is not cleared with clearTimeout.
* Instead, the function is no-oped.
*
* @param func - The function to debounce.
* @param wait - The wait time in milliseconds.
* @returns The debounced function.
*/
private debounce<K extends keyof T>(func: Listener<T[K]>, wait: number): Listener<T[K]> {
// Create a timeout variable.
let timeout: ReturnType<typeof setTimeout>;
return (detail: T[K]) => {
// If a debounce timer is already pending, clear it before scheduling the next one.
if (timeout !== undefined) {
clearTimeout(timeout);
}
timeout = setTimeout(() => {
func(detail);
}, wait);
};
}
/**
* Make a function cancellable.
* @param func - The function to make cancelable.
* @returns The cancellable function with a cancel method.
*/
private cancellable<K extends keyof T>(func: Listener<T[K]>): { cancel: () => void; listener: Listener<T[K]> } {
let cancelled = false;
return {
cancel: (): boolean => (cancelled = true),
listener: (detail: T[K]): void => {
if (cancelled) return;
func(detail);
},
};
}
}
+1
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@@ -1,3 +1,4 @@
export * from './event-emitter.ts';
export * from './extended-json.ts';
export * from './script.ts';
export * from './sse-session/index.ts';
+22
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@@ -0,0 +1,22 @@
import type { DeeplyReadonly } from './types';
/**
* Recursively freezes an object by iterating over all properties and freezing them.
* @param obj - The object to freeze.
* @returns The frozen object.
*/
export const deepFreeze = <T>(value: T): DeeplyReadonly<T> => {
if (value !== null && (typeof value === 'object' || typeof value === 'function')) {
for (const key of Reflect.ownKeys(value)) {
const descriptor = Reflect.getOwnPropertyDescriptor(value, key);
if (descriptor && 'value' in descriptor) {
deepFreeze(descriptor.value);
}
}
Object.freeze(value);
}
return value;
};
+8
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@@ -0,0 +1,8 @@
/**
* A deeply readonly type.
* @template T - The type to make deeply readonly.
* @returns The deeply readonly type.
*/
export type DeeplyReadonly<T> = {
readonly [K in keyof T]: T[K] extends (...args: never[]) => unknown ? T[K] : DeeplyReadonly<T[K]>;
};
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@@ -0,0 +1,819 @@
import { expect, test, vi } from 'vitest';
import { EventEmitter } from '../source/event-emitter.ts';
import type { DeeplyReadonly } from '../source/types.ts';
import { deepFreeze } from '../source/misc.ts';
/** Simple event map used across these tests. */
type TestEvents = {
message: string;
count: number;
readonly: Readonly<{ value: number }>;
deeplyReadonly: DeeplyReadonly<{ nested: { value: number } }>;
};
/**
* Tests that EventEmitter invokes listeners when an event is emitted.
*/
const testEventEmitterCallsListeners = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
// Register the listener and emit an event.
emitter.on('message', listener);
emitter.emit('message', 'hello');
// Expect the listener to have been called with the emitted payload.
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith('hello');
};
/**
* Tests that EventEmitter invokes all listeners registered for the same event.
*/
const testEventEmitterCallsMultipleListeners = (): void => {
const emitter = new EventEmitter<TestEvents>();
const firstListener = vi.fn();
const secondListener = vi.fn();
// Register two listeners for the same event type.
emitter.on('count', firstListener);
emitter.on('count', secondListener);
emitter.emit('count', 42);
// Expect both listeners to receive the same payload.
expect(firstListener).toHaveBeenCalledOnce();
expect(firstListener).toHaveBeenCalledWith(42);
expect(secondListener).toHaveBeenCalledOnce();
expect(secondListener).toHaveBeenCalledWith(42);
};
/**
* Tests that EventEmitter only invokes listeners registered for the emitted event type.
*/
const testEventEmitterCallsOnlyMatchingListeners = (): void => {
const emitter = new EventEmitter<TestEvents>();
const messageListener = vi.fn();
const countListener = vi.fn();
// Register listeners on different event types.
emitter.on('message', messageListener);
emitter.on('count', countListener);
// Emit only the message event.
emitter.emit('message', 'hello');
// Expect only the matching listener to have been called.
expect(messageListener).toHaveBeenCalledOnce();
expect(countListener).not.toHaveBeenCalled();
};
/**
* Tests that EventEmitter.emit returns false when no listeners are registered.
*/
const testEventEmitterEmitReturnsFalseWithNoListeners = (): void => {
const emitter = new EventEmitter<TestEvents>();
const hasListeners = emitter.emit('message', 'hello');
// Expect emit to report that nobody was listening.
expect(hasListeners).toBe(false);
};
/**
* Tests that EventEmitter.emit returns true when listeners are registered.
*/
const testEventEmitterEmitReturnsTrueWithListeners = (): void => {
const emitter = new EventEmitter<TestEvents>();
emitter.on('message', vi.fn());
const hasListeners = emitter.emit('message', 'hello');
// Expect emit to report that at least one listener was invoked.
expect(hasListeners).toBe(true);
};
/**
* Tests that EventEmitter.emit continues after a listener throws an error.
*/
const testEventEmitterEmitContinuesAfterListenerThrows = (): void => {
const emitter = new EventEmitter<TestEvents>();
const secondListener = vi.fn();
emitter.on('message', (): void => {
throw new Error('listener failure');
});
emitter.on('message', secondListener);
emitter.emit('message', 'hello');
expect(secondListener).toHaveBeenCalledOnce();
expect(secondListener).toHaveBeenCalledWith('hello');
};
/**
* Tests that it supports Object.freeze() frozen payloads.
*/
const testEventEmitterSupportsObjectFreezeFrozenPayloads = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
const payload = Object.freeze({ value: 42 });
emitter.on('readonly', listener, 100);
emitter.emit('readonly', payload);
// @ts-expect-error - We are trying to mutate a frozen payload.
expect(() => (payload.value = 43)).toThrow();
// Advance the timer to ensure the debounce timer goes off
await vi.advanceTimersByTimeAsync(100);
// Expect the listener to have been called with the frozen payload.
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith(payload);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that it supports deepFreeze() frozen payloads.
*/
const testEventEmitterSupportsDeepFreezeFrozenPayloads = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
const payload = deepFreeze({ nested: { value: 42 } });
emitter.on('deeplyReadonly', listener, 100);
emitter.emit('deeplyReadonly', payload);
// @ts-expect-error - We are trying to mutate a frozen payload.
expect(() => (payload.nested.value = 43)).toThrow();
// Advance the timer to ensure the debounce timer goes off
await vi.advanceTimersByTimeAsync(100);
// Expect the listener to have been called with the frozen payload.
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith(payload);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that the off callback returned by on() removes the listener.
*/
const testEventEmitterOffCallbackRemovesListener = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
// on() returns an off callback that removes the listener.
const off = emitter.on('message', listener);
emitter.emit('message', 'first');
// Unsubscribe before emitting again.
off();
emitter.emit('message', 'second');
// Expect the listener to have only received the first event.
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith('first');
};
/**
* Tests that off() removes a listener when given the same function reference.
*/
const testEventEmitterOffRemovesListenerByReference = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.on('message', listener);
emitter.off('message', listener);
emitter.emit('message', 'hello');
// Expect the listener to have been removed before the emit.
expect(listener).not.toHaveBeenCalled();
};
/**
* Tests that off() removes all listeners for an event type when no listener is provided.
*/
const testEventEmitterOffRemovesAllListenersForEventType = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.on('message', listener);
emitter.off('message');
expect(listener).not.toHaveBeenCalled();
expect(emitter.emit('message', 'hello')).toBe(false);
expect(emitter.emit('count', 42)).toBe(false);
};
/**
* Tests that off() does nothing when given an unknown listener reference.
*/
const testEventEmitterOffIgnoresUnknownListener = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.on('message', listener);
// Try to remove a different function reference.
emitter.off('message', vi.fn());
emitter.emit('message', 'hello');
// Expect the original listener to still receive the event.
expect(listener).toHaveBeenCalledOnce();
};
/**
* Tests that off() does nothing when called for an event type with no listeners.
*/
const testEventEmitterOffIgnoresUnregisteredEventType = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
// Call off without ever registering this listener.
emitter.off('message', listener);
expect(listener).not.toHaveBeenCalled();
};
/**
* Tests that once() listeners are invoked only one time.
*/
const testEventEmitterOnceListenerFiresOnce = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.once('message', listener);
emitter.emit('message', 'first');
emitter.emit('message', 'second');
// Expect the listener to auto-unsubscribe after the first emit.
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith('first');
};
/**
* Tests that once() can be added when regular listeners already exist for the event type.
*/
const testEventEmitterOnceWorksWithExistingListeners = (): void => {
const emitter = new EventEmitter<TestEvents>();
const existingListener = vi.fn();
const onceListener = vi.fn();
// Register a regular listener first so the event type already exists in the map.
emitter.on('message', existingListener);
emitter.once('message', onceListener);
emitter.emit('message', 'hello');
expect(existingListener).toHaveBeenCalledOnce();
expect(onceListener).toHaveBeenCalledOnce();
};
/**
* Tests that the off callback returned by once() removes the listener before it fires.
*/
const testEventEmitterOnceOffCallbackRemovesListener = (): void => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
const off = emitter.once('message', listener);
// Unsubscribe before the event is ever emitted.
off();
emitter.emit('message', 'hello');
expect(listener).not.toHaveBeenCalled();
};
/**
* Tests that debounced listeners do not receive the debounced event if the listener is removed.
*/
const testEventEmitterOffCancelsPendingDebouncedCallback = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
const off = emitter.on('message', listener, 100);
emitter.emit('message', 'first');
off();
emitter.emit('message', 'second');
await vi.advanceTimersByTimeAsync(100);
expect(listener).not.toHaveBeenCalled();
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that removeAllListeners() clears every registered listener.
*/
const testEventEmitterRemoveAllListeners = (): void => {
const emitter = new EventEmitter<TestEvents>();
const messageListener = vi.fn();
const countListener = vi.fn();
emitter.on('message', messageListener);
emitter.on('count', countListener);
emitter.removeAllListeners();
// Emit on both event types after clearing all listeners.
emitter.emit('message', 'hello');
emitter.emit('count', 1);
expect(messageListener).not.toHaveBeenCalled();
expect(countListener).not.toHaveBeenCalled();
};
/**
* Tests that removeAllListeners() cancels a pending debounced callback.
*/
const testEventEmitterRemoveAllListenersCancelsPendingDebouncedCallback = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
// Arm a debounce timer, then clear every listener before it expires.
emitter.on('message', listener, 100);
emitter.emit('message', 'should not arrive');
emitter.removeAllListeners();
await vi.advanceTimersByTimeAsync(100);
// Cleared listeners must not receive delayed debounced delivery.
expect(listener).not.toHaveBeenCalled();
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that timeouts are eventually cleared when removeAllListeners is called.
*/
const testEventEmitterTimeoutsAreClearedAfterTheyRunWhenRemoveAllListenersIsCalled = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.on('message', listener, 100);
emitter.emit('message', 'pending');
// We expect there to be a timer since we emitted a debounced event
expect(vi.getTimerCount()).toBe(1);
// Remove all listeners
emitter.removeAllListeners();
// Advance the timer to ensure the debounce timer is cleared.
await vi.advanceTimersByTimeAsync(100);
// Make sure the listener was not called
expect(listener).not.toHaveBeenCalled();
// Make sure the timer was cleared
expect(vi.getTimerCount()).toBe(0);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that timeouts are eventually cleared when off is called.
*/
const testEventEmitterTimeoutsAreClearedWhenOffIsCalled = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
const off = emitter.on('message', listener, 100);
emitter.emit('message', 'pending');
// We expect there to be a timer since we emitted a debounced event
expect(vi.getTimerCount()).toBe(1);
// Cancel the listener
off();
// Advance the timer to ensure the debounce timer is cleared.
await vi.advanceTimersByTimeAsync(100);
// Make sure the listener was not called
expect(listener).not.toHaveBeenCalled();
// Make sure the timer was cleared
expect(vi.getTimerCount()).toBe(0);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that waitFor() resolves when a matching event is emitted.
*/
const testEventEmitterWaitForResolvesOnMatch = async (): Promise<void> => {
const emitter = new EventEmitter<TestEvents>();
// Wait until an event matches the predicate.
const waitPromise = emitter.waitFor('count', (payload) => payload === 42);
// Emit a non-matching event first, then the matching one.
emitter.emit('count', 41);
emitter.emit('count', 42);
await expect(waitPromise).resolves.toBe(42);
};
/**
* Tests that waitFor() ignores non-matching events while other listeners still receive them.
*/
const testEventEmitterWaitForIgnoresNonMatchingEvents = async (): Promise<void> => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
const waitPromise = emitter.waitFor('message', (payload) => payload === 'done');
// A regular listener should still receive every emit while waitFor filters.
emitter.on('message', listener);
emitter.emit('message', 'pending');
emitter.emit('message', 'done');
await expect(waitPromise).resolves.toBe('done');
expect(listener).toHaveBeenCalledTimes(2);
};
/**
* Tests that waitFor() rejects when the timeout expires.
*/
const testEventEmitterWaitForRejectsOnTimeout = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const waitPromise = emitter.waitFor('message', () => true, 100);
// Attach the rejection handler before advancing timers so the rejection is handled.
const assertion = expect(waitPromise).rejects.toThrow('Timeout waiting for event "message"');
await vi.advanceTimersByTimeAsync(100);
await assertion;
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that waitFor() clears its timeout when it resolves before expiry.
*/
const testEventEmitterWaitForClearsTimeoutOnResolve = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
// Register waitFor with a timeout, then resolve it before the timer fires.
const waitPromise = emitter.waitFor('message', (payload) => payload === 'done', 100);
emitter.emit('message', 'done');
await expect(waitPromise).resolves.toBe('done');
// If clearTimeout was not called, advancing past the timeout would reject the promise.
await vi.advanceTimersByTimeAsync(100);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that waitFor() removes its listener after resolving.
*/
const testEventEmitterWaitForRemovesListenerAfterResolve = async (): Promise<void> => {
const emitter = new EventEmitter<TestEvents>();
const waitPromise = emitter.waitFor('message', () => true);
emitter.emit('message', 'first');
await expect(waitPromise).resolves.toBe('first');
// Register a second waitFor so we can verify the first listener was cleaned up.
const secondWaitPromise = emitter.waitFor('message', (payload) => payload === 'second');
// Emit a payload that only the second waitFor should accept.
emitter.emit('message', 'ignored');
// Track whether the second waitFor resolves too early.
let resolvedEarly = false;
/* eslint-disable-next-line */
secondWaitPromise.then(() => {
resolvedEarly = true;
});
// Yield so any premature resolution would have a chance to run.
await Promise.resolve();
expect(resolvedEarly).toBe(false);
emitter.emit('message', 'second');
await expect(secondWaitPromise).resolves.toBe('second');
};
/**
* Tests that the first debounced emit does not call clearTimeout.
*/
const testEventEmitterDebouncedFirstEmitDoesNotClearTimeout = (): void => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const clearTimeoutSpy = vi.spyOn(globalThis, 'clearTimeout');
const listener = vi.fn();
emitter.on('message', listener, 100);
emitter.emit('message', 'first');
// The first emit starts the debounce timer; there is nothing to clear yet.
expect(clearTimeoutSpy).not.toHaveBeenCalled();
expect(listener).not.toHaveBeenCalled();
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that debounced on() listeners receive only the last payload after the debounce window.
*/
const testEventEmitterDebouncedOnListener = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.on('message', listener, 100);
// Emit several events in quick succession.
emitter.emit('message', 'first');
emitter.emit('message', 'second');
emitter.emit('message', 'third');
// Expect the listener to not have fired yet.
expect(listener).not.toHaveBeenCalled();
// Advance past the debounce window.
await vi.advanceTimersByTimeAsync(100);
// Expect only the last payload to have been delivered.
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith('third');
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that repeated debounced emits reset the debounce timer.
*/
const testEventEmitterDebouncedTimerResetsOnRepeatedEmits = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.on('count', listener, 100);
emitter.emit('count', 1);
// Advance halfway through the debounce window and emit again.
await vi.advanceTimersByTimeAsync(50);
emitter.emit('count', 2);
await vi.advanceTimersByTimeAsync(50);
// The timer was reset, so the listener should not have fired yet.
expect(listener).not.toHaveBeenCalled();
// Advance the remaining time for the reset timer to expire.
await vi.advanceTimersByTimeAsync(50);
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith(2);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that a debounce time of zero behaves like a normal listener.
*/
const testEventEmitterZeroDebounceDoesNotDebounce = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
// A debounce time of zero should behave like a normal listener.
emitter.on('message', listener, 0);
emitter.emit('message', 'first');
emitter.emit('message', 'second');
expect(listener).toHaveBeenCalledTimes(2);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that debounced once() listeners fire once with the last payload.
*/
const testEventEmitterDebouncedOnceListener = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
emitter.once('message', listener, 100);
emitter.emit('message', 'first');
emitter.emit('message', 'second');
await vi.advanceTimersByTimeAsync(100);
// Expect the debounced once listener to fire once with the last payload.
expect(listener).toHaveBeenCalledOnce();
expect(listener).toHaveBeenCalledWith('second');
// Emit again after the debounce window; the once listener should stay removed.
emitter.emit('message', 'third');
await vi.advanceTimersByTimeAsync(100);
expect(listener).toHaveBeenCalledOnce();
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
/**
* Tests that the `waitFor` method rejects if the predicate function throws
*/
const testEventEmitterWaitForRejectsOnPredicateError = async (): Promise<void> => {
const emitter = new EventEmitter<TestEvents>();
const listener = vi.fn();
const waitPromise = emitter.waitFor('message', () => {
throw new Error('predicate error');
});
emitter.emit('message', 'hello');
await expect(waitPromise).rejects.toThrow('predicate error');
expect(listener).not.toHaveBeenCalled();
};
/**
* Tests that waitFor() removes its listener after the predicate function throws an error.
*/
const testEventEmitterWaitForRemovesListenerAfterPredicateError = async (): Promise<void> => {
const emitter = new EventEmitter<TestEvents>();
// Create a predicate function that throws an error.
const predicate = vi.fn().mockImplementation(() => {
throw new Error('predicate error');
});
// Wait for the predicate function to throw an error.
const waitPromise = emitter.waitFor('message', predicate);
// Emit an event, expecting the predicate function to throw an error.
emitter.emit('message', 'hello');
await expect(waitPromise).rejects.toThrow('predicate error');
// Expect the predicate function to have been called once.
expect(predicate).toHaveBeenCalledTimes(1);
// A later emit must not invoke the failed waitFor predicate again.
emitter.emit('message', 'again');
// Expect the predicate function to still have been called once.
expect(predicate).toHaveBeenCalledTimes(1);
};
/**
* Tests that waitFor() clears its timeout when the predicate function throws an error.
*/
const testEventEmitterWaitForClearsTimeoutAfterPredicateError = async (): Promise<void> => {
vi.useFakeTimers();
try {
const emitter = new EventEmitter<TestEvents>();
const clearTimeoutSpy = vi.spyOn(globalThis, 'clearTimeout');
const waitPromise = emitter.waitFor(
'message',
(): boolean => {
throw new Error('predicate error');
},
100,
);
emitter.emit('message', 'hello');
await expect(waitPromise).rejects.toThrow('predicate error');
// The timeout scheduled for waitFor must be cleared on predicate failure.
expect(clearTimeoutSpy).toHaveBeenCalled();
// Advancing past the original timeout must not produce a second rejection path.
await vi.advanceTimersByTimeAsync(100);
} finally {
vi.useRealTimers();
vi.restoreAllMocks();
}
};
const runTests = async (): Promise<void> => {
test('EventEmitter: calls listeners when an event is emitted', testEventEmitterCallsListeners);
test('EventEmitter: calls multiple listeners for the same event', testEventEmitterCallsMultipleListeners);
test('EventEmitter: only calls listeners for the emitted event type', testEventEmitterCallsOnlyMatchingListeners);
test('EventEmitter: returns false when emitting with no listeners', testEventEmitterEmitReturnsFalseWithNoListeners);
test('EventEmitter: returns true when emitting with listeners', testEventEmitterEmitReturnsTrueWithListeners);
test('EventEmitter: continues after a listener throws an error', testEventEmitterEmitContinuesAfterListenerThrows);
test('EventEmitter: supports Object.freeze() frozen payloads', testEventEmitterSupportsObjectFreezeFrozenPayloads);
test('EventEmitter: supports deepFreeze() frozen payloads', testEventEmitterSupportsDeepFreezeFrozenPayloads);
test('EventEmitter: stops calling a listener after its off callback is invoked', testEventEmitterOffCallbackRemovesListener);
test('EventEmitter: removes a listener when off is called with the same reference', testEventEmitterOffRemovesListenerByReference);
test(
'EventEmitter: removes all listeners for an event type when off is called with no listener',
testEventEmitterOffRemovesAllListenersForEventType,
);
test('EventEmitter: ignores off when the listener reference is unknown', testEventEmitterOffIgnoresUnknownListener);
test('EventEmitter: ignores off for an event type with no listeners', testEventEmitterOffIgnoresUnregisteredEventType);
test('EventEmitter: calls a once listener only one time', testEventEmitterOnceListenerFiresOnce);
test('EventEmitter: registers once when listeners already exist', testEventEmitterOnceWorksWithExistingListeners);
test('EventEmitter: stops a once listener after its off callback is invoked', testEventEmitterOnceOffCallbackRemovesListener);
test(
'EventEmitter: debounced listeners do not receive the debounced event if the listener is removed',
testEventEmitterOffCancelsPendingDebouncedCallback,
);
test('EventEmitter: removes all listeners when removeAllListeners is called', testEventEmitterRemoveAllListeners);
test(
'EventEmitter: cancels a pending debounced callback when removeAllListeners is called',
testEventEmitterRemoveAllListenersCancelsPendingDebouncedCallback,
);
test(
'EventEmitter: timeouts are cleared after they run when removeAllListeners is called',
testEventEmitterTimeoutsAreClearedAfterTheyRunWhenRemoveAllListenersIsCalled,
);
test('EventEmitter: timeouts are cleared when off is called', testEventEmitterTimeoutsAreClearedWhenOffIsCalled);
test('EventEmitter: resolves waitFor when a matching event is emitted', testEventEmitterWaitForResolvesOnMatch);
test('EventEmitter: ignores non-matching events while waiting with waitFor', testEventEmitterWaitForIgnoresNonMatchingEvents);
test('EventEmitter: rejects waitFor when the timeout is reached', testEventEmitterWaitForRejectsOnTimeout);
test('EventEmitter: clears the timeout when waitFor resolves before expiry', testEventEmitterWaitForClearsTimeoutOnResolve);
test('EventEmitter: removes the waitFor listener after it resolves', testEventEmitterWaitForRemovesListenerAfterResolve);
test('EventEmitter: does not clear a timeout on the first debounced emit', testEventEmitterDebouncedFirstEmitDoesNotClearTimeout);
test('EventEmitter: debounces on listeners', testEventEmitterDebouncedOnListener);
test('EventEmitter: resets the debounce timer on repeated emits', testEventEmitterDebouncedTimerResetsOnRepeatedEmits);
test('EventEmitter: does not debounce when debounceMilliseconds is zero', testEventEmitterZeroDebounceDoesNotDebounce);
test('EventEmitter: debounces once listeners and invokes them only once', testEventEmitterDebouncedOnceListener);
test('EventEmitter: rejects waitFor when the predicate function throws', testEventEmitterWaitForRejectsOnPredicateError);
test(
'EventEmitter: removes the waitFor listener after it rejects due to predicate error',
testEventEmitterWaitForRemovesListenerAfterPredicateError,
);
test('EventEmitter: clears the timeout when waitFor rejects due to predicate error', testEventEmitterWaitForClearsTimeoutAfterPredicateError);
};
await runTests();