From 6fa85f3d1ec6e9368bf2ee981a0c08c8dc898c19 Mon Sep 17 00:00:00 2001
From: Lukas Taegert-Atkinson <lukas.taegert-atkinson@tngtech.com>
Date: Sun, 6 Mar 2022 07:38:05 +0100
Subject: [PATCH] Extract emitter and improve coverage

---
 src/watch/WatchEmitter.ts | 48 +++++++++++++++++++++++++++++++++++++++
 src/watch/watch-proxy.ts  | 45 +-----------------------------------
 2 files changed, 49 insertions(+), 44 deletions(-)
 create mode 100644 src/watch/WatchEmitter.ts

diff --git a/src/watch/WatchEmitter.ts b/src/watch/WatchEmitter.ts
new file mode 100644
index 00000000000..edc68f85471
--- /dev/null
+++ b/src/watch/WatchEmitter.ts
@@ -0,0 +1,48 @@
+import { EventEmitter } from 'events';
+
+type PromiseReturn<T extends (...args: any) => any> = (
+	...args: Parameters<T>
+) => Promise<ReturnType<T>>;
+
+export class WatchEmitter<
+	T extends { [event: string]: (...args: any) => any }
+> extends EventEmitter {
+	private awaitedHandlers: {
+		[K in keyof T]?: PromiseReturn<T[K]>[];
+	} = Object.create(null);
+
+	constructor() {
+		super();
+		// Allows more than 10 bundles to be watched without
+		// showing the `MaxListenersExceededWarning` to the user.
+		this.setMaxListeners(Infinity);
+	}
+
+	// Will be overwritten by Rollup
+	async close(): Promise<void> {}
+
+	emitAndAwait<K extends keyof T>(
+		event: K,
+		...args: Parameters<T[K]>
+	): Promise<ReturnType<T[K]>[]> {
+		this.emit(event as string, ...(args as any[]));
+		return Promise.all(this.getHandlers(event).map(handler => handler(...args)));
+	}
+
+	onCurrentAwaited<K extends keyof T>(
+		event: K,
+		listener: (...args: Parameters<T[K]>) => Promise<ReturnType<T[K]>>
+	): this {
+		this.getHandlers(event).push(listener);
+		return this;
+	}
+
+	removeAwaited(): this {
+		this.awaitedHandlers = {};
+		return this;
+	}
+
+	private getHandlers<K extends keyof T>(event: K): PromiseReturn<T[K]>[] {
+		return this.awaitedHandlers[event] || (this.awaitedHandlers[event] = []);
+	}
+}
diff --git a/src/watch/watch-proxy.ts b/src/watch/watch-proxy.ts
index 487a3365708..b7371b0398a 100644
--- a/src/watch/watch-proxy.ts
+++ b/src/watch/watch-proxy.ts
@@ -1,53 +1,10 @@
-import { EventEmitter } from 'events';
 import type { RollupWatcher } from '../rollup/types';
 import { ensureArray } from '../utils/ensureArray';
 import { errInvalidOption, error } from '../utils/error';
 import type { GenericConfigObject } from '../utils/options/options';
+import { WatchEmitter } from './WatchEmitter';
 import { loadFsEvents } from './fsevents-importer';
 
-class WatchEmitter<T extends { [event: string]: (...args: any) => any }> extends EventEmitter {
-	private awaitedHandlers: {
-		[K in keyof T]?: ((...args: Parameters<T[K]>) => Promise<ReturnType<T[K]>>)[];
-	} = {};
-
-	constructor() {
-		super();
-		// Allows more than 10 bundles to be watched without
-		// showing the `MaxListenersExceededWarning` to the user.
-		this.setMaxListeners(Infinity);
-	}
-
-	// Will be overwritten by Rollup
-	async close(): Promise<void> {}
-
-	emitAndAwait<K extends keyof T>(
-		event: K,
-		...args: Parameters<T[K]>
-	): Promise<ReturnType<T[K]>[]> {
-		this.emit(event as string, ...(args as any[]));
-		const handlers = this.awaitedHandlers[event];
-		if (!handlers) return Promise.resolve([]);
-		return Promise.all(handlers.map(handler => handler(...args)));
-	}
-
-	onCurrentAwaited<K extends keyof T>(
-		event: K,
-		listener: (...args: Parameters<T[K]>) => Promise<ReturnType<T[K]>>
-	): this {
-		let handlers = this.awaitedHandlers[event];
-		if (!handlers) {
-			handlers = this.awaitedHandlers[event] = [];
-		}
-		handlers.push(listener);
-		return this;
-	}
-
-	removeAwaited(): this {
-		this.awaitedHandlers = {};
-		return this;
-	}
-}
-
 export default function watch(configs: GenericConfigObject[] | GenericConfigObject): RollupWatcher {
 	const emitter = new WatchEmitter() as RollupWatcher;
 	const configArray = ensureArray(configs);