Avoid memory leaks via beforeExit listeners

src/utils/hookActions.ts

@@ -1,4 +1,3 @@
-import { EventEmitter } from 'node:events';
 import process from 'node:process';
 import type { HookAction, PluginDriver } from './PluginDriver';
 
@@ -25,33 +24,40 @@ function formatAction([pluginName, hookName, parameters]: HookAction): string {
 	return action;
 }
 
-// We do not directly listen on process to avoid max listeners warnings for
-// complicated build processes
-const beforeExitEvent = 'beforeExit';
-// eslint-disable-next-line unicorn/prefer-event-target
-const beforeExitEmitter = new EventEmitter();
-beforeExitEmitter.setMaxListeners(0);
-process.on(beforeExitEvent, () => beforeExitEmitter.emit(beforeExitEvent));
+let handleBeforeExit: null | (() => void) = null;
+const rejectByPluginDriver = new Map<PluginDriver, (reason: Error) => void>();
 
 export async function catchUnfinishedHookActions<T>(
 	pluginDriver: PluginDriver,
 	callback: () => Promise<T>
 ): Promise<T> {
-	let handleEmptyEventLoop: () => void;
 	const emptyEventLoopPromise = new Promise<T>((_, reject) => {
-		handleEmptyEventLoop = () => {
-			const unfulfilledActions = pluginDriver.getUnfulfilledHookActions();
-			reject(
-				new Error(
-					`Unexpected early exit. This happens when Promises returned by plugins cannot resolve. Unfinished hook action(s) on exit:\n` +
-						[...unfulfilledActions].map(formatAction).join('\n')
-				)
-			);
-		};
-		beforeExitEmitter.once(beforeExitEvent, handleEmptyEventLoop);
+		rejectByPluginDriver.set(pluginDriver, reject);
+		if (!handleBeforeExit) {
+			// We only ever create a single event listener to avoid max listener and
+			// other issues
+			handleBeforeExit = () => {
+				for (const [pluginDriver, reject] of rejectByPluginDriver) {
+					const unfulfilledActions = pluginDriver.getUnfulfilledHookActions();
+					reject(
+						new Error(
+							`Unexpected early exit. This happens when Promises returned by plugins cannot resolve. Unfinished hook action(s) on exit:\n` +
+								[...unfulfilledActions].map(formatAction).join('\n')
+						)
+					);
+				}
+			};
+			process.once('beforeExit', handleBeforeExit);
+		}
 	});
 
-	const result = await Promise.race([callback(), emptyEventLoopPromise]);
-	beforeExitEmitter.off(beforeExitEvent, handleEmptyEventLoop!);
-	return result;
+	try {
+		return await Promise.race([callback(), emptyEventLoopPromise]);
+	} finally {
+		rejectByPluginDriver.delete(pluginDriver);
+		if (rejectByPluginDriver.size === 0) {
+			process.off('beforeExit', handleBeforeExit!);
+			handleBeforeExit = null;
+		}
+	}
 }

test/watch/index.js

@@ -10,7 +10,7 @@ const { copy } = require('fs-extra');
 const rollup = require('../../dist/rollup');
 const { atomicWriteFileSync, wait } = require('../utils');
 
-describe.only('rollup.watch', () => {
+describe('rollup.watch', () => {
 	let watcher;
 
 	beforeEach(() => {