fix: Failing with remaining tests (Windows)

This change ensures that all messages from the worker are received by
the main process before the worker exits.

It solves issues on Windows that are occurring with Node.js v20 and later
when `workerThreads: false` is set in the AVA configuration.

Fixes: #3390

Author: matz3

lib/fork.js

@@ -104,6 +104,11 @@ export default function loadFork(file, options, execArgv = process.execArgv) {
 			}
 
 			switch (message.ava.type) {
+				case 'worker-finished': {
+					send({type: 'worker-should-exit'});
+					break;
+				}
+
 				case 'ready-for-options': {
 					send({type: 'options', options});
 					break;

lib/worker/base.js

@@ -120,6 +120,15 @@ const run = async options => {
 			return;
 		}
 
+		channel.send({type: 'worker-finished'});
+
+		// As the channel has already been unreferenced
+		// we need to reference it again to wait for the worker-should-exit message.
+		// Otherwise the process may exit prematurely, especially on Windows.
+		channel.ref();
+		await channel.workerShouldExit;
+		channel.unref();
+
 		nowAndTimers.setImmediate(() => {
 			const unhandled = currentlyUnhandled();
 			if (unhandled.length === 0) {

lib/worker/channel.cjs

@@ -107,7 +107,9 @@ handle.ref();
 
 exports.options = selectAvaMessage(handle.channel, 'options').then(message => message.ava.options);
 exports.peerFailed = selectAvaMessage(handle.channel, 'peer-failed');
+exports.workerShouldExit = selectAvaMessage(handle.channel, 'worker-should-exit');
 exports.send = handle.send.bind(handle);
+exports.ref = handle.ref.bind(handle);
 exports.unref = handle.unref.bind(handle);
 
 let channelCounter = 0;

test/child-process/fixtures/package.json

@@ -0,0 +1,3 @@
+{
+	"type": "module"
+}

test/child-process/fixtures/test.js

@@ -0,0 +1,7 @@
+import test from 'ava';
+
+for (let i = 0; i < 50; i++) {
+	test("Test " + (i + 1), (t) => {
+		t.true(true);
+	});
+}

test/child-process/test.js

@@ -0,0 +1,9 @@
+import test from '@ava/test';
+
+import {fixture} from '../helpers/exec.js';
+
+// Regression test for https://github.com/avajs/ava/issues/3390
+test('running 50 tests in a child process works as expected', async t => {
+	const result = await fixture(['--no-worker-threads']);
+	t.is(result.stats.passed.length, 50);
+});