worker: support relative paths

doc/api/errors.md

@@ -1741,10 +1741,11 @@ The fulfilled value of a linking promise is not a `vm.Module` object.
 The current module's status does not allow for this operation. The specific
 meaning of the error depends on the specific function.
 
-<a id="ERR_WORKER_NEED_ABSOLUTE_PATH"></a>
-### ERR_WORKER_NEED_ABSOLUTE_PATH
+<a id="ERR_WORKER_PATH"></a>
+### ERR_WORKER_PATH
 
-The path for the main script of a worker is not an absolute path.
+The path for the main script of a worker is neither an absolute path
+nor a relative path starting with `./` or `../`.
 
 <a id="ERR_WORKER_UNSERIALIZABLE_ERROR"></a>
 ### ERR_WORKER_UNSERIALIZABLE_ERROR

doc/api/worker_threads.md

@@ -306,7 +306,9 @@ if (isMainThread) {
 
 ### new Worker(filename, options)
 
-* `filename` {string} The absolute path to the Worker’s main script.
+* `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 `../`.
   If `options.eval` is true, this is a string containing JavaScript code rather
   than a path.
 * `options` {Object}

lib/internal/errors.js

@@ -847,8 +847,9 @@ E('ERR_VM_MODULE_NOT_LINKED',
 E('ERR_VM_MODULE_NOT_MODULE',
   'Provided module is not an instance of Module', Error);
 E('ERR_VM_MODULE_STATUS', 'Module status %s', Error);
-E('ERR_WORKER_NEED_ABSOLUTE_PATH',
-  'The worker script filename must be an absolute path. Received "%s"',
+E('ERR_WORKER_PATH',
+  'The worker script filename must be an absolute path or a relative ' +
+  'path starting with \'./\' or \'../\'. Received "%s"',
   TypeError);
 E('ERR_WORKER_UNSERIALIZABLE_ERROR',
   'Serializing an uncaught exception failed', Error);

lib/internal/worker.js

@@ -7,7 +7,7 @@ const util = require('util');
 const { Readable, Writable } = require('stream');
 const {
   ERR_INVALID_ARG_TYPE,
-  ERR_WORKER_NEED_ABSOLUTE_PATH,
+  ERR_WORKER_PATH,
   ERR_WORKER_UNSERIALIZABLE_ERROR,
   ERR_WORKER_UNSUPPORTED_EXTENSION,
 } = require('internal/errors').codes;
@@ -212,9 +212,15 @@ class Worker extends EventEmitter {
     }
 
     if (!options.eval) {
-      if (!path.isAbsolute(filename)) {
-        throw new ERR_WORKER_NEED_ABSOLUTE_PATH(filename);
+      if (!path.isAbsolute(filename) &&
+          !filename.startsWith('./') &&
+          !filename.startsWith('../') &&
+          !filename.startsWith('.' + path.sep) &&
+          !filename.startsWith('..' + path.sep)) {
+        throw new ERR_WORKER_PATH(filename);
       }
+      filename = path.resolve(filename);
+
       const ext = path.extname(filename);
       if (ext !== '.js' && ext !== '.mjs') {
         throw new ERR_WORKER_UNSUPPORTED_EXTENSION(ext);

test/parallel/test-worker-relative-path-double-dot.js

@@ -0,0 +1,17 @@
+// Flags: --experimental-worker
+'use strict';
+const path = require('path');
+const assert = require('assert');
+const common = require('../common');
+const { Worker, isMainThread, parentPort } = require('worker_threads');
+
+if (isMainThread) {
+  const cwdName = path.relative('../', '.');
+  const relativePath = path.relative('.', __filename);
+  const w = new Worker(path.join('..', cwdName, relativePath));
+  w.on('message', common.mustCall((message) => {
+    assert.strictEqual(message, 'Hello, world!');
+  }));
+} else {
+  parentPort.postMessage('Hello, world!');
+}

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

@@ -0,0 +1,15 @@
+// Flags: --experimental-worker
+'use strict';
+const path = require('path');
+const assert = require('assert');
+const common = require('../common');
+const { Worker, isMainThread, parentPort } = require('worker_threads');
+
+if (isMainThread) {
+  const w = new Worker('./' + path.relative('.', __filename));
+  w.on('message', common.mustCall((message) => {
+    assert.strictEqual(message, 'Hello, world!');
+  }));
+} else {
+  parentPort.postMessage('Hello, world!');
+}

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

@@ -1,21 +1,11 @@
 // Flags: --experimental-worker
 'use strict';
 
+const path = require('path');
 const common = require('../common');
 const assert = require('assert');
 const { Worker } = require('worker_threads');
 
-{
-  const expectedErr = common.expectsError({
-    code: 'ERR_WORKER_NEED_ABSOLUTE_PATH',
-    type: TypeError
-  }, 4);
-  assert.throws(() => { new Worker('a.js'); }, expectedErr);
-  assert.throws(() => { new Worker('b'); }, expectedErr);
-  assert.throws(() => { new Worker('c/d.js'); }, expectedErr);
-  assert.throws(() => { new Worker('a.mjs'); }, expectedErr);
-}
-
 {
   const expectedErr = common.expectsError({
     code: 'ERR_WORKER_UNSUPPORTED_EXTENSION',
@@ -25,3 +15,15 @@ const { Worker } = require('worker_threads');
   assert.throws(() => { new Worker('/c.wasm'); }, expectedErr);
   assert.throws(() => { new Worker('/d.txt'); }, expectedErr);
 }
+
+{
+  const expectedErr = common.expectsError({
+    code: 'ERR_WORKER_PATH',
+    type: TypeError
+  }, 4);
+  const existingRelPathNoDot = path.relative('.', __filename);
+  assert.throws(() => { new Worker(existingRelPathNoDot); }, expectedErr);
+  assert.throws(() => { new Worker('relative_no_dot'); }, expectedErr);
+  assert.throws(() => { new Worker('file:///file_url'); }, expectedErr);
+  assert.throws(() => { new Worker('https://www.url.com'); }, expectedErr);
+}