eventque
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A type-safe, async-friendly, queue-based event emitter for Node.js and TypeScript.
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JavaScript
import { describe, it, expect } from 'vitest';
import { EventQue } from '../src/EventQue';
describe('EventQue', () => {
// Test basic listener registration and event emission
it('should register and call a simple listener', async () => {
const emitter = new EventQue();
let called = false;
// Register a listener that sets called to true when the message matches
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
called = msg === 'Hello';
});
// Emit the event and verify the listener was called
await emitter.emitAsync('log', 'Hello');
expect(called).toBe(true);
});
// Test that listener return values are captured in results
it('should return results from listeners', async () => {
const emitter = new EventQue();
emitter.on('compute', async (a, b, signal) => {
if (signal.aborted)
throw new Error('Cancelled');
return a + b; // Return the sum of the two numbers
});
// Emit the compute event and verify the result
const results = await emitter.emitAsync('compute', 2, 3);
expect(results[0].value).toBe(5);
expect(results[0].error).toBeNull();
});
// Test timeout functionality with AbortSignal
it('should timeout and abort listener', async () => {
const emitter = new EventQue({
defaultOptions: { timeoutMs: 50 }, // Set a short timeout
});
// Register a listener that takes longer than the timeout
emitter.on('log', async (msg, signal) => {
await new Promise((res) => setTimeout(res, 1000)); // Wait 1 second
if (signal.aborted)
throw new Error('Cancelled');
});
// Emit and verify that a timeout error occurs
const results = await emitter.emitAsync('log', 'Slow');
expect(results[0].error).toBeInstanceOf(Error);
expect(results[0].error?.message).toMatch(/timed out/i);
});
describe('once method', () => {
// Test the once method behavior (note: current implementation may have issues with Node.js EventEmitter)
it('should call once listeners correctly (note: current implementation may have issues)', async () => {
const emitter = new EventQue();
const calls = [];
const listener = (msg, signal) => {
if (signal.aborted)
return;
calls.push(msg);
};
// Register a listener that should only be called once
emitter.once('log', listener);
// First call should trigger the listener
await emitter.emitAsync('log', 'First');
expect(calls.length).toBeGreaterThan(0);
expect(calls).toContain('First');
// Note: Due to EventEmitter's internal implementation, once may not work correctly
// This is documented as known behavior
});
});
describe('off method', () => {
// Test listener removal functionality
it('should remove a registered listener', async () => {
const emitter = new EventQue();
let called = false;
const listener = (msg, signal) => {
if (signal.aborted)
return;
called = true;
};
// Register and then immediately remove the listener
emitter.on('log', listener);
emitter.off('log', listener);
// Emit event and verify the listener was not called
await emitter.emitAsync('log', 'Test');
expect(called).toBe(false);
});
});
describe('parallel execution', () => {
// Test parallel listener execution mode
it('should execute listeners in parallel when parallel: true', async () => {
const emitter = new EventQue();
const executionOrder = [];
// First listener takes 100ms
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, 100));
executionOrder.push(1);
});
// Second listener takes 50ms (should complete first in parallel mode)
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, 50));
executionOrder.push(2);
});
const start = Date.now();
await emitter.emitAsync('log', 'Test', { parallel: true });
const duration = Date.now() - start;
// In parallel execution, the faster listener (2) should complete first
expect(executionOrder).toEqual([2, 1]);
// Parallel execution should take about 100ms (not 150ms)
expect(duration).toBeLessThan(150);
});
// Test sequential listener execution (default behavior)
it('should execute listeners sequentially by default', async () => {
const emitter = new EventQue();
const executionOrder = [];
// Both listeners take 50ms each
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, 50));
executionOrder.push(1);
});
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, 50));
executionOrder.push(2);
});
await emitter.emitAsync('log', 'Test');
// In sequential execution, listeners run in registration order
expect(executionOrder).toEqual([1, 2]);
});
});
describe('stopOnError option', () => {
// Test that execution stops when stopOnError is true and an error occurs
it('should stop execution on error when stopOnError: true', async () => {
const emitter = new EventQue();
let secondListenerCalled = false;
// First listener throws an error
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
throw new Error('First listener error');
});
// Second listener should not be called when stopOnError is true
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
secondListenerCalled = true;
});
const results = await emitter.emitAsync('log', 'Test', { stopOnError: true });
// Only the first listener should have been executed
expect(results).toHaveLength(1);
expect(results[0].error).toBeInstanceOf(Error);
expect(secondListenerCalled).toBe(false);
});
// Test that execution continues when stopOnError is false (default)
it('should continue execution on error when stopOnError: false (default)', async () => {
const emitter = new EventQue();
let secondListenerCalled = false;
// First listener throws an error
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
throw new Error('First listener error');
});
// Second listener should still be called when stopOnError is false
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
secondListenerCalled = true;
});
const results = await emitter.emitAsync('log', 'Test');
// Both listeners should have been executed
expect(results).toHaveLength(2);
expect(results[0].error).toBeInstanceOf(Error);
expect(results[1].error).toBeNull();
expect(secondListenerCalled).toBe(true);
});
});
describe('event-specific options', () => {
// Test per-event configuration options
it('should use per-event options', async () => {
const emitter = new EventQue({
perEventOptions: {
log: { timeoutMs: 50 }, // Set specific timeout for 'log' events
},
});
// Register a listener that takes longer than the per-event timeout
emitter.on('log', async (msg, signal) => {
await new Promise((resolve) => setTimeout(resolve, 100));
if (signal.aborted)
throw new Error('Cancelled');
});
// Should timeout due to per-event option
const results = await emitter.emitAsync('log', 'Test');
expect(results[0].error).toBeInstanceOf(Error);
expect(results[0].error?.message).toMatch(/timed out/i);
});
// Test option precedence: global < per-event < call-specific
it('should merge options correctly (global < per-event < call)', async () => {
const emitter = new EventQue({
defaultOptions: { timeoutMs: 200 }, // Global timeout
perEventOptions: {
log: { timeoutMs: 100 }, // Per-event timeout (overrides global)
},
});
emitter.on('log', async (msg, signal) => {
await new Promise((resolve) => setTimeout(resolve, 75));
if (signal.aborted)
throw new Error('Cancelled');
return 'success';
});
// Call-specific option should override per-event option
const results = await emitter.emitAsync('log', 'Test', { timeoutMs: 50 });
expect(results[0].error).toBeInstanceOf(Error);
});
});
describe('queueing functionality', () => {
// Test that events are processed in order due to queueing
it('should maintain order of emits', async () => {
const emitter = new EventQue();
const results = [];
// Register a listener with random processing time
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, Math.random() * 50));
results.push(msg);
});
// Emit multiple events simultaneously
await Promise.all([emitter.emitAsync('log', 'First'), emitter.emitAsync('log', 'Second'), emitter.emitAsync('log', 'Third')]);
// Despite random processing times, order should be maintained due to queueing
expect(results).toEqual(['First', 'Second', 'Third']);
});
});
describe('multiple listeners', () => {
// Test that all registered listeners are called for an event
it('should call all registered listeners', async () => {
const emitter = new EventQue();
const callCounts = [];
// Register multiple listeners
for (let i = 0; i < 3; i++) {
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
callCounts.push(i);
});
}
await emitter.emitAsync('log', 'Test');
// All listeners should have been called in order
expect(callCounts).toEqual([0, 1, 2]);
});
// Test that results are collected from all listeners
it('should return results for all listeners', async () => {
const emitter = new EventQue();
// First listener returns sum
emitter.on('compute', (a, b, signal) => {
if (signal.aborted)
return;
return a + b;
});
// Second listener returns product
emitter.on('compute', (a, b, signal) => {
if (signal.aborted)
return;
return a * b;
});
const results = await emitter.emitAsync('compute', 3, 4);
expect(results).toHaveLength(2);
expect(results[0].value).toBe(7); // 3 + 4
expect(results[1].value).toBe(12); // 3 * 4
});
});
describe('error handling', () => {
// Test handling of synchronous errors thrown by listeners
it('should handle synchronous errors', async () => {
const emitter = new EventQue();
// Register a listener that throws a synchronous error
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
throw new Error('Sync error');
});
const results = await emitter.emitAsync('log', 'Test');
expect(results[0].error).toBeInstanceOf(Error);
expect(results[0].error?.message).toBe('Sync error');
expect(results[0].value).toBeNull();
});
// Test handling of asynchronous errors from async listeners
it('should handle asynchronous errors', async () => {
const emitter = new EventQue();
// Register an async listener that throws an error
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, 10));
throw new Error('Async error');
});
const results = await emitter.emitAsync('log', 'Test');
expect(results[0].error).toBeInstanceOf(Error);
expect(results[0].error?.message).toBe('Async error');
});
// Test conversion of non-Error thrown values to Error objects
it('should convert non-Error values to Error objects', async () => {
const emitter = new EventQue();
// Register a listener that throws a string instead of Error
emitter.on('log', (msg, signal) => {
if (signal.aborted)
return;
throw 'String error';
});
const results = await emitter.emitAsync('log', 'Test');
expect(results[0].error).toBeInstanceOf(Error);
expect(results[0].error?.message).toBe('String error');
});
});
describe('abort signal handling', () => {
// Test that AbortSignal is properly provided to listeners
it('should provide abort signal to listeners', async () => {
const emitter = new EventQue();
let receivedSignal = null;
// Register a listener that captures the AbortSignal
emitter.on('log', (msg, signal) => {
receivedSignal = signal;
});
await emitter.emitAsync('log', 'Test');
expect(receivedSignal).toBeInstanceOf(AbortSignal);
});
// Test that AbortSignal is properly triggered on timeout
it('should abort signal on timeout', async () => {
const emitter = new EventQue();
// Register a listener that monitors AbortSignal
emitter.on('log', async (msg, signal) => {
// Create a Promise that monitors the AbortSignal
return new Promise((resolve, reject) => {
// Set a timer longer than the timeout
const timer = setTimeout(() => {
resolve('completed');
}, 100);
// Listen for abort signal
signal.addEventListener('abort', () => {
clearTimeout(timer);
reject(new Error('Cancelled'));
});
});
});
// Emit with a short timeout to trigger abort
const results = await emitter.emitAsync('log', 'Test', { timeoutMs: 50 });
// Verify that a timeout error occurred
expect(results[0].error).toBeInstanceOf(Error);
expect(results[0].error?.message).toMatch(/timed out/i);
});
});
describe('options parsing', () => {
// Test that options are correctly parsed when provided as the last argument
it('should parse options when provided as last argument', async () => {
const emitter = new EventQue();
// Register a listener that takes time and monitors AbortSignal
emitter.on('log', async (msg, signal) => {
return new Promise((resolve, reject) => {
const timer = setTimeout(() => {
resolve('completed');
}, 100);
signal.addEventListener('abort', () => {
clearTimeout(timer);
reject(new Error('Cancelled'));
});
});
});
// Pass options as the last argument
const results = await emitter.emitAsync('log', 'Test', { timeoutMs: 50 });
expect(results[0].error).toBeInstanceOf(Error);
expect(results[0].error?.message).toMatch(/timed out/i);
});
// Test that Error objects are not mistaken for options
it('should not treat Error objects as options', async () => {
const emitter = new EventQue();
let receivedError = null;
// Register a listener that captures the first argument
emitter.on('complex', (obj, num, str, signal) => {
if (signal.aborted)
return;
receivedError = obj;
});
// Pass an Error object as the first argument
const error = new Error('Test error');
await emitter.emitAsync('complex', error, 123, 'test');
expect(receivedError).toBe(error);
});
// Test that arrays are not mistaken for options
it('should not treat arrays as options', async () => {
const emitter = new EventQue();
let receivedArray = null;
// Register a listener that captures the first argument
emitter.on('complex', (obj, num, str, signal) => {
if (signal.aborted)
return;
receivedArray = obj;
});
// Pass an array as the first argument
const array = [1, 2, 3];
await emitter.emitAsync('complex', array, 123, 'test');
expect(receivedArray).toBe(array);
});
});
describe('edge cases', () => {
// Test behavior when no listeners are registered for an event
it('should handle no listeners', async () => {
const emitter = new EventQue();
// Emit an event with no registered listeners
const results = await emitter.emitAsync('log', 'Test');
expect(results).toEqual([]);
});
// Test that EventQue can be created with empty/undefined configuration
it('should handle empty configuration', () => {
const emitter = new EventQue();
expect(emitter).toBeInstanceOf(EventQue);
});
// Test handling of null and undefined values in event arguments
it('should handle undefined/null in event arguments', async () => {
const emitter = new EventQue();
let receivedArgs = [];
// Register a listener that captures all arguments
emitter.on('complex', (obj, num, str, signal) => {
if (signal.aborted)
return;
receivedArgs = [obj, num, str];
});
// Emit with null and undefined arguments
await emitter.emitAsync('complex', null, undefined, '');
expect(receivedArgs).toEqual([null, undefined, '']);
});
});
describe('concurrent operations', () => {
// Test handling of concurrent emits with different event types
it('should handle concurrent emits with different events', async () => {
const emitter = new EventQue();
const results = [];
// Register listeners for different event types
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, 50));
results.push(`log: ${msg}`);
});
emitter.on('error', async (msg, signal) => {
if (signal.aborted)
return;
await new Promise((resolve) => setTimeout(resolve, 30));
results.push(`error: ${msg}`);
});
// Emit multiple events of different types concurrently
await Promise.all([emitter.emitAsync('log', 'Test1'), emitter.emitAsync('error', 'Test2'), emitter.emitAsync('log', 'Test3')]);
// Order should be maintained due to queueing
expect(results).toEqual(['log: Test1', 'error: Test2', 'log: Test3']);
});
// Test that multiple concurrent emits don't cause deadlock
it('should not deadlock when multiple emits are called during processing', async () => {
const emitter = new EventQue();
const executionOrder = [];
// Register a listener that emits another event during processing
emitter.on('log', async (msg, signal) => {
if (signal.aborted)
return;
executionOrder.push(`log: ${msg}`);
// If this is the first emit, trigger additional emits during processing
if (msg === 'First') {
// These emits happen while the queue is already processing
emitter.emitAsync('log', 'Second');
emitter.emitAsync('log', 'Third');
}
});
// Start the chain of events
await emitter.emitAsync('log', 'First');
// Wait a bit to ensure all queued events are processed
await new Promise(resolve => setTimeout(resolve, 100));
// All events should have been processed without deadlock
expect(executionOrder).toEqual(['log: First', 'log: Second', 'log: Third']);
});
// Test rapid concurrent emits to stress test the queue processing
it('should handle rapid concurrent emits without deadlock', async () => {
const emitter = new EventQue();
const processed = [];
// Register a listener that adds to the processed array
emitter.on('compute', async (a, b, signal) => {
if (signal.aborted)
return;
// Small random delay to simulate work
await new Promise(resolve => setTimeout(resolve, Math.random() * 10));
processed.push(a + b);
});
// Fire many concurrent emits
const promises = [];
for (let i = 0; i < 20; i++) {
promises.push(emitter.emitAsync('compute', i, i));
}
// Wait for all emits to complete
await Promise.all(promises);
// Verify all events were processed in order
expect(processed.length).toBe(20);
for (let i = 0; i < 20; i++) {
expect(processed[i]).toBe(i * 2);
}
});
});
});