worker_threads: allow URL in Worker constructor

The explicit goal is to let users use `import.meta.url` to re-load thecurrent module inside a Worker instance.

Fixes: nodejs#30780

doc/api/worker_threads.md

@@ -513,6 +513,10 @@ if (isMainThread) {
 <!-- YAML
 added: v10.5.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/31664
+    description: The `filename` parameter can be a WHATWG `URL` object using
+                 `file:` protocol.
   - version: v13.2.0
     pr-url: https://github.com/nodejs/node/pull/26628
     description: The `resourceLimits` option was introduced.
@@ -521,9 +525,10 @@ changes:
     description: The `argv` option was introduced.
 -->
 
-* `filename` {string} The path to the Worker’s main script. Must be
-  either an absolute path or a relative path (i.e. relative to the
-  current working directory) starting with `./` or `../`.
+* `filename` {string|URL} The path to the Worker’s main script or module. Must
+  be either an absolute path or a relative path (i.e. relative to the
+  current working directory) starting with `./` or `../`, or a WHATWG `URL`
+  object using `file:` protocol.
   If `options.eval` is `true`, this is a string containing JavaScript code
   rather than a path.
 * `options` {Object}
@@ -536,8 +541,9 @@ changes:
     to specify that the parent thread and the child thread should share their
     environment variables; in that case, changes to one thread’s `process.env`
     object will affect the other thread as well. **Default:** `process.env`.
-  * `eval` {boolean} If `true`, interpret the first argument to the constructor
-    as a script that is executed once the worker is online.
+  * `eval` {boolean} If `true` and the first argument is a `string`, interpret
+    the first argument to the constructor as a script that is executed once the
+    worker is online.
   * `execArgv` {string[]} List of node CLI options passed to the worker.
     V8 options (such as `--max-old-space-size`) and options that affect the
     process (such as `--title`) are not supported. If set, this will be provided

lib/internal/errors.js

@@ -1394,9 +1394,14 @@ E('ERR_WORKER_INVALID_EXEC_ARGV', (errors, msg = 'invalid execArgv flags') =>
 E('ERR_WORKER_NOT_RUNNING', 'Worker instance not running', Error);
 E('ERR_WORKER_OUT_OF_MEMORY',
   'Worker terminated due to reaching memory limit: %s', Error);
-E('ERR_WORKER_PATH',
-  'The worker script filename must be an absolute path or a relative ' +
-  'path starting with \'./\' or \'../\'. Received "%s"',
+E('ERR_WORKER_PATH', (filename) =>
+  'The worker script or module filename must be an absolute path or a ' +
+  'relative path starting with \'./\' or \'../\'.' +
+  (filename.startsWith('file://') ?
+    ' If you want to pass a file:// URL, you must wrap it around `new URL`.' :
+    ''
+  ) +
+  ` Received "${filename}"`,
   TypeError);
 E('ERR_WORKER_UNSERIALIZABLE_ERROR',
   'Serializing an uncaught exception failed', Error);

lib/internal/url.js

@@ -1348,8 +1348,7 @@ function getPathFromURLPosix(url) {
 function fileURLToPath(path) {
   if (typeof path === 'string')
     path = new URL(path);
-  else if (path == null || !path[searchParams] ||
-           !path[searchParams][searchParams])
+  else if (!isURLInstance(path))
     throw new ERR_INVALID_ARG_TYPE('path', ['string', 'URL'], path);
   if (path.protocol !== 'file:')
     throw new ERR_INVALID_URL_SCHEME('file');
@@ -1396,9 +1395,13 @@ function pathToFileURL(filepath) {
   return outURL;
 }
 
+function isURLInstance(fileURLOrPath) {
+  return fileURLOrPath != null && fileURLOrPath[searchParams] &&
+    fileURLOrPath[searchParams][searchParams];
+}
+
 function toPathIfFileURL(fileURLOrPath) {
-  if (fileURLOrPath == null || !fileURLOrPath[searchParams] ||
-      !fileURLOrPath[searchParams][searchParams])
+  if (!isURLInstance(fileURLOrPath))
     return fileURLOrPath;
   return fileURLToPath(fileURLOrPath);
 }
@@ -1431,6 +1434,7 @@ module.exports = {
   fileURLToPath,
   pathToFileURL,
   toPathIfFileURL,
+  isURLInstance,
   URL,
   URLSearchParams,
   domainToASCII,

lib/internal/worker.js

@@ -27,8 +27,8 @@ const {
   ERR_INVALID_ARG_TYPE,
   // eslint-disable-next-line no-unused-vars
   ERR_WORKER_INIT_FAILED,
+  ERR_INVALID_ARG_VALUE,
 } = errorCodes;
-const { validateString } = require('internal/validators');
 const { getOptionValue } = require('internal/options');
 
 const workerIo = require('internal/worker/io');
@@ -45,7 +45,7 @@ const {
   WritableWorkerStdio
 } = workerIo;
 const { deserializeError } = require('internal/error-serdes');
-const { pathToFileURL } = require('url');
+const { fileURLToPath, isURLInstance, pathToFileURL } = require('internal/url');
 
 const {
   ownsProcessState,
@@ -86,7 +86,6 @@ class Worker extends EventEmitter {
   constructor(filename, options = {}) {
     super();
     debug(`[${threadId}] create new worker`, filename, options);
-    validateString(filename, 'filename');
     if (options.execArgv && !ArrayIsArray(options.execArgv)) {
       throw new ERR_INVALID_ARG_TYPE('options.execArgv',
                                      'Array',
@@ -99,11 +98,33 @@ class Worker extends EventEmitter {
       }
       argv = options.argv.map(String);
     }
-    if (!options.eval) {
-      if (!path.isAbsolute(filename) && !/^\.\.?[\\/]/.test(filename)) {
+
+    let url;
+    if (options.eval) {
+      if (typeof filename !== 'string') {
+        throw new ERR_INVALID_ARG_VALUE(
+          'options.eval',
+          options.eval,
+          'must be false when \'filename\' is not a string'
+        );
+      }
+      url = null;
+    } else {
+      if (isURLInstance(filename)) {
+        url = filename;
+        filename = fileURLToPath(filename);
+      } else if (typeof filename !== 'string') {
+        throw new ERR_INVALID_ARG_TYPE(
+          'filename',
+          ['string', 'URL'],
+          filename
+        );
+      } else if (path.isAbsolute(filename) || /^\.\.?[\\/]/.test(filename)) {
+        filename = path.resolve(filename);
+        url = pathToFileURL(filename);
+      } else {
         throw new ERR_WORKER_PATH(filename);
       }
-      filename = path.resolve(filename);
 
       const ext = path.extname(filename);
       if (ext !== '.js' && ext !== '.mjs' && ext !== '.cjs') {
@@ -125,7 +146,6 @@ class Worker extends EventEmitter {
         options.env);
     }
 
-    const url = options.eval ? null : pathToFileURL(filename);
     // Set up the C++ handle for the worker, as well as some internal wiring.
     this[kHandle] = new WorkerImpl(url,
                                    env === process.env ? null : env,

test/parallel/test-worker-type-check.js

@@ -20,7 +20,8 @@ const { Worker } = require('worker_threads');
       {
         code: 'ERR_INVALID_ARG_TYPE',
         name: 'TypeError',
-        message: 'The "filename" argument must be of type string.' +
+        message: 'The "filename" argument must be of type string ' +
+                 'or an instance of URL.' +
                  common.invalidArgTypeHelper(val)
       }
     );

test/parallel/test-worker-unsupported-eval-on-url.mjs

@@ -0,0 +1,6 @@
+import '../common/index.mjs';
+import assert from 'assert';
+import { Worker } from 'worker_threads';
+
+const re = /The argument 'options\.eval' must be false when 'filename' is not a string\./;
+assert.throws(() => new Worker(new URL(import.meta.url), { eval: true }), re);

test/parallel/test-worker-unsupported-path.js

@@ -13,6 +13,7 @@ const { Worker } = require('worker_threads');
   assert.throws(() => { new Worker('/b'); }, expectedErr);
   assert.throws(() => { new Worker('/c.wasm'); }, expectedErr);
   assert.throws(() => { new Worker('/d.txt'); }, expectedErr);
+  assert.throws(() => { new Worker(new URL('file:///e.wasm')); }, expectedErr);
 }
 
 {
@@ -26,3 +27,26 @@ const { Worker } = require('worker_threads');
   assert.throws(() => { new Worker('file:///file_url'); }, expectedErr);
   assert.throws(() => { new Worker('https://www.url.com'); }, expectedErr);
 }
+
+{
+  assert.throws(
+    () => { new Worker('file:///file_url'); },
+    /If you want to pass a file:\/\/ URL, you must wrap it around `new URL`/
+  );
+  assert.throws(
+    () => { new Worker('relative_no_dot'); },
+    // eslint-disable-next-line node-core/no-unescaped-regexp-dot
+    /^((?!If you want to pass a file:\/\/ URL, you must wrap it around `new URL`).)*$/s
+  );
+}
+
+{
+  const expectedErr = {
+    code: 'ERR_INVALID_URL_SCHEME',
+    name: 'TypeError'
+  };
+  assert.throws(() => { new Worker(new URL('https://www.url.com')); },
+                expectedErr);
+  assert.throws(() => { new Worker(new URL('data:application/javascript,')); },
+                expectedErr);
+}

test/parallel/test-worker.mjs

@@ -0,0 +1,18 @@
+import { mustCall } from '../common/index.mjs';
+import assert from 'assert';
+import { Worker, isMainThread, parentPort } from 'worker_threads';
+
+const TEST_STRING = 'Hello, world!';
+
+if (isMainThread) {
+  const w = new Worker(new URL(import.meta.url));
+  w.on('message', mustCall((message) => {
+    assert.strictEqual(message, TEST_STRING);
+  }));
+} else {
+  setImmediate(() => {
+    process.nextTick(() => {
+      parentPort.postMessage(TEST_STRING);
+    });
+  });
+}