added ESM support for worker scripts

src/worker.js

@@ -1,4 +1,5 @@
 'use strict';
+const url = require('url');
 const worker = require('worker_threads');
 const Movable = require('./movable');
 const { OP_YIELD, OP_RESPONSE, OP_CALLBACK, OP_GENERATOR, OP_READY, WOP_REQUEST, WOP_CALLBACK } = require('./constants');
@@ -24,8 +25,13 @@ worker.workerData = worker.workerData.workerData;
 worker.parentPort = new worker.MessageChannel().port1;
 
 // Load the user's worker script. It may export a promise.
-// TODO: add support for ESM files
-Promise.resolve(require(FILENAME)).then((methods) => {
+new Promise((resolve) => {
+	try {
+		resolve(require(FILENAME));
+	} catch (_) {
+		resolve(import(url.pathToFileURL(FILENAME).href));
+	}
+}).then((methods) => {
 	if (typeof methods !== 'object' || methods === null) {
 		throw new TypeError('Worker must export an object');
 	}

test/basic.js

@@ -5,6 +5,7 @@ const { expect } = require('chai');
 const ThreadPool = require('..');
 
 const WORKER = require.resolve('./workers/worker.js');
+const WORKER_ESM = require.resolve('./workers/worker-esm.mjs');
 const INVALID_WORKER = require.resolve('./workers/invalid-worker.js');
 const INVALID_WORKER_ASYNC = require.resolve('./workers/invalid-worker-async.js');
 const INVALID_WORKER_EXPORT = require.resolve('./workers/invalid-worker-export.js');
@@ -39,9 +40,6 @@ describe('basic functionality', function () {
 			expect(() => new ThreadPool({ filename: 'workers/worker.js' })).to.throw(TypeError);
 			expect(() => new ThreadPool({ filename: 'test/workers/worker.js' })).to.throw(TypeError);
 		});
-		it('does not accept windows-style absolute paths for the filename', function () {
-			expect(() => new ThreadPool({ filename: path.win32.normalize(WORKER) })).to.throw(TypeError);
-		});
 		it('does not accept non-JS file extensions in the filename', function () {
 			expect(() => new ThreadPool({ filename: WORKER.slice(0, -3) + '.css' })).to.throw(TypeError);
 			expect(() => new ThreadPool({ filename: WORKER.slice(0, -3) + '.jsx' })).to.throw(TypeError);
@@ -90,6 +88,10 @@ describe('basic functionality', function () {
 				});
 			});
 		});
+		it('accepts worker scripts as ESM modules', async function () {
+			pool = new ThreadPool({ filename: WORKER_ESM });
+			expect(await pool.call('echo', 123)).to.deep.equal([123]);
+		});
 	});
 
 	describe('ThreadPool properties', function () {

test/workers/worker-esm.mjs

@@ -0,0 +1,3 @@
+export function echo(...args) {
+	return args;
+}