worker: add support for Web Workers

Author: avivkeller

doc/api/cli.md

@@ -1527,6 +1527,14 @@ changes:
 
 Enable experimental WebAssembly System Interface (WASI) support.
 
+### `--experimental-web-worker`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+Enable experimental support for the Web Worker API.
+
 ### `--experimental-worker-inspection`
 
 <!-- YAML

doc/api/globals.md

@@ -1310,6 +1310,15 @@ changes:
 A browser-compatible implementation of {WebSocket}. Disable this API
 with the [`--no-experimental-websocket`][] CLI flag.
 
+## Class: `Worker`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+A browser-compatible implementation of Web Workers. Enable this API
+with the [`--experimental-web-worker`][] CLI flag.
+
 ## Class: `WritableStream`
 
 <!-- YAML
@@ -1359,6 +1368,7 @@ A browser-compatible implementation of [`WritableStreamDefaultWriter`][].
 [RFC 5646]: https://www.rfc-editor.org/rfc/rfc5646.txt
 [Web Crypto API]: webcrypto.md
 [`--experimental-eventsource`]: cli.md#--experimental-eventsource
+[`--experimental-web-worker`]: cli.md#--experimental-web-worker
 [`--localstorage-file`]: cli.md#--localstorage-filefile
 [`--no-experimental-global-navigator`]: cli.md#--no-experimental-global-navigator
 [`--no-experimental-websocket`]: cli.md#--no-experimental-websocket

doc/node.1

@@ -820,6 +820,9 @@ Enable experimental ES Module support in the \fBnode:vm\fR module.
 .It Fl -experimental-wasi-unstable-preview1
 Enable experimental WebAssembly System Interface (WASI) support.
 .
+.It Fl -experimental-web-worker
+Enable experimental support for the Web Worker API.
+.
 .It Fl -experimental-worker-inspection
 Enable experimental support for the worker inspection with Chrome DevTools.
 .

lib/internal/blob.js

@@ -30,7 +30,7 @@ const {
 } = internalBinding('buffer');
 
 const {
-  TextDecoder,
+  getUtf8Decoder,
   TextEncoder,
 } = require('internal/encoding');
 const { URL } = require('internal/url');
@@ -88,7 +88,6 @@ let ReadableStream;
 let TextDecoderStream;
 
 const enc = new TextEncoder();
-let dec;
 
 // Yes, lazy loading is annoying but because of circular
 // references between the url, internal/blob, and buffer
@@ -312,7 +311,7 @@ class Blob {
     if (!isBlob(this))
       return PromiseReject(new ERR_INVALID_THIS('Blob'));
 
-    dec ??= new TextDecoder();
+    const dec = getUtf8Decoder();
 
     return PromisePrototypeThen(
       arrayBuffer(this),
@@ -466,6 +465,43 @@ function arrayBuffer(blob) {
   return promise;
 }
 
+/**
+ * Read a blob's data synchronously. This is only possible when every part
+ * of the blob is memory-resident, in which case the reader's pull callbacks
+ * are invoked synchronously; otherwise (e.g. for file-backed blobs)
+ * undefined is returned.
+ * @param {Blob} blob
+ * @returns {ArrayBuffer|undefined}
+ */
+function getBlobDataSync(blob) {
+  const reader = blob[kHandle].getReader();
+  const buffers = [];
+  let result;
+  let ended = false;
+  while (!ended) {
+    let sync = false;
+    reader.pull((status, buffer) => {
+      sync = true;
+      if (status === 0) {
+        // EOS; buffer should be undefined here.
+        result = concat(buffers);
+        ended = true;
+        return;
+      } else if (status < 0) {
+        ended = true;
+        return;
+      }
+      if (buffer !== undefined)
+        ArrayPrototypePush(buffers, buffer);
+    });
+    if (!sync) {
+      // The data is not available synchronously.
+      break;
+    }
+  }
+  return result;
+}
+
 function createBlobReaderStream(reader) {
   return new lazyReadableStream({
     type: 'bytes',
@@ -644,6 +680,7 @@ module.exports = {
   createBlobFromFilePath,
   createBlobReaderIterable,
   createBlobReaderStream,
+  getBlobDataSync,
   isBlob,
   kHandle,
   resolveObjectURL,

lib/internal/bootstrap/web/exposed-window-or-worker.js

@@ -51,6 +51,8 @@ exposeLazyInterfaces(globalThis, 'internal/worker/io', ['BroadcastChannel']);
 exposeLazyInterfaces(globalThis, 'internal/worker/io', [
   'MessageChannel', 'MessagePort',
 ]);
+// https://html.spec.whatwg.org/multipage/workers.html#dedicated-workers-and-the-worker-interface
+exposeLazyInterfaces(globalThis, 'internal/webworker', ['Worker']);
 // https://www.w3.org/TR/FileAPI/#dfn-Blob
 exposeLazyInterfaces(globalThis, 'internal/blob', ['Blob']);
 // https://www.w3.org/TR/FileAPI/#dfn-file

lib/internal/encoding.js

@@ -614,8 +614,17 @@ ObjectDefineProperties(TextDecoder.prototype, {
   },
 });
 
+// A lazily created TextDecoder for the common case of decoding UTF-8 with
+// the default options, shared between internal modules.
+let utf8Decoder;
+function getUtf8Decoder() {
+  utf8Decoder ??= new TextDecoder();
+  return utf8Decoder;
+}
+
 module.exports = {
   getEncodingFromLabel,
+  getUtf8Decoder,
   TextDecoder,
   TextEncoder,
 };

lib/internal/event_target.js

@@ -722,7 +722,10 @@ class EventTarget {
       return;
 
     type = webidl.converters.DOMString(type);
-    const capture = options?.capture === true;
+    // Flatten the options argument like addEventListener does.
+    // Refs: https://dom.spec.whatwg.org/#concept-flatten-options
+    const capture = typeof options === 'boolean' ?
+      options : options?.capture === true;
 
     if (this[kEvents] === undefined)
       return;
@@ -1163,6 +1166,13 @@ function defineEventHandler(emitter, name, event = name) {
 
   function set(value) {
     validateThisInternalField(this, kHandlers, 'EventTarget');
+    // Event handler IDL attributes are [LegacyTreatNonObjectAsNull]: values
+    // that are neither callable nor objects deactivate the handler.
+    // Refs: https://html.spec.whatwg.org/multipage/webappapis.html#event-handler-idl-attributes
+    if (typeof value !== 'function' &&
+        (typeof value !== 'object' || value === null)) {
+      value = null;
+    }
     if (this[kHandlers] === undefined)
       this[kHandlers] = new SafeMap();
     let wrappedHandler = this[kHandlers].get(event);

lib/internal/main/worker_thread.js

@@ -100,6 +100,7 @@ port.on('message', (message) => {
       hasStdin,
       publicPort,
       workerData,
+      webWorkerData,
       mainThreadPort,
     } = message;
 
@@ -116,6 +117,11 @@ port.on('message', (message) => {
     require('internal/worker').assignEnvironmentData(environmentData);
     setupMainThreadPort(mainThreadPort);
 
+    if (webWorkerData !== undefined) {
+      require('internal/webworker')
+        .installDedicatedWorkerGlobalScope(webWorkerData.url, webWorkerData);
+    }
+
     // The counter is only passed to the workers created by the main thread,
     // not to workers created by other workers.
     let cachedCwd = '';
@@ -155,7 +161,14 @@ port.on('message', (message) => {
         break;
       }
 
-      case 'classic': if (getOptionValue('--input-type') !== 'module') {
+      case 'classic': if (webWorkerData?.source !== undefined) {
+        // The source of a classic web Worker script loaded from a blob: or
+        // data: URL. Unlike a worker eval, "run a classic script" evaluates
+        // the source in the worker's global scope.
+        require('internal/webworker')
+          .runClassicScriptSource(webWorkerData.source, webWorkerData.url);
+        break;
+      } else if (getOptionValue('--input-type') !== 'module') {
         const name = '[worker eval]';
         // This is necessary for CJS module compilation.
         // TODO: pass this with something really internal.

lib/internal/modules/helpers.js

@@ -446,8 +446,6 @@ function assertBufferSource(body, allowString, hookName) {
   );
 }
 
-let DECODER = null;
-
 /**
  * Converts a buffer or buffer-like object to a string.
  * @param {string | ArrayBuffer | ArrayBufferView} body - The buffer or buffer-like object to convert to a string.
@@ -456,9 +454,7 @@ let DECODER = null;
 function stringify(body) {
   if (typeof body === 'string') { return body; }
   assertBufferSource(body, false, 'load');
-  const { TextDecoder } = require('internal/encoding');
-  DECODER = DECODER === null ? new TextDecoder() : DECODER;
-  return DECODER.decode(body);
+  return require('internal/encoding').getUtf8Decoder().decode(body);
 }
 
 /**

lib/internal/navigator.js

@@ -159,6 +159,7 @@ ObjectDefineProperties(Navigator.prototype, {
 
 module.exports = {
   getNavigatorPlatform,
+  kInitialize,
   navigator: new Navigator(kInitialize),
   Navigator,
 };