Fix Webpack erroring with worker_threads import, unref Worker so process can terminate

packages/ac3/src/worker-client.ts

@@ -10,13 +10,51 @@ import { assert, type WorkerCommand, type WorkerResponse, type WorkerResponseDat
 // @ts-expect-error An esbuild plugin handles this, TypeScript doesn't need to understand
 import createWorker from './codec.worker';
 
-let workerPromise: Promise<Worker> | null;
+type ExtendedWorker = Worker & {
+	ref?: () => void;
+	unref?: () => void;
+};
+
+let workerPromise: Promise<ExtendedWorker> | null;
 let nextMessageId = 0;
 const pendingMessages = new Map<number, {
 	resolve: (value: WorkerResponseData) => void;
 	reject: (reason?: unknown) => void;
 }>();
 
+let refCount = 0;
+let keepAliveInterval: ReturnType<typeof setInterval> | null = null;
+
+export const refWorker = async () => {
+	refCount++;
+	if (refCount === 1) {
+		keepAliveInterval = setInterval(() => {}, 2 ** 31 - 1);
+		const worker = await ensureWorker();
+		worker.ref?.();
+	}
+};
+
+export const unrefWorker = async () => {
+	refCount--;
+	if (refCount === 0) {
+		if (keepAliveInterval !== null) {
+			clearInterval(keepAliveInterval);
+			keepAliveInterval = null;
+		}
+
+		const worker = await workerPromise;
+		if (worker) {
+			if (worker.unref) {
+				worker.unref(); // If we don't do this, then the Node process never terminates by itself
+			} else if (typeof window === 'undefined') {
+				// Non-browser environment without unref - terminate instead
+				worker.terminate();
+				workerPromise = null;
+			}
+		}
+	}
+};
+
 export const sendCommand = async <T extends string>(
 	command: WorkerCommand & { type: T },
 	transferables?: Transferable[],
@@ -41,7 +79,8 @@ export const sendCommand = async <T extends string>(
 const ensureWorker = () => {
 	return workerPromise ??= (async () => {
 		// eslint-disable-next-line @typescript-eslint/no-unsafe-call
-		const worker = (await createWorker()) as Worker;
+		const worker = (await createWorker()) as ExtendedWorker;
+		worker.unref?.(); // Start unreffed
 
 		const onMessage = (data: WorkerResponse) => {
 			const pending = pendingMessages.get(data.id);