Provide option to delete Deno namespace in worker (#2717)

js/compiler.ts

@@ -25,7 +25,7 @@ const console = new Console(core.print);
 window.console = console;
 window.workerMain = workerMain;
 export default function denoMain(): void {
-  os.start("TS");
+  os.start(true, "TS");
 }
 
 const ASSETS = "$asset$";

js/core.ts

@@ -1,4 +1,6 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
 import { window } from "./window";
 
+// This allows us to access core in API even if we
+// dispose window.Deno
 export const core = window.Deno.core as DenoCore;

js/globals.ts

@@ -32,7 +32,6 @@ import * as request from "./request";
 // These imports are not exposed and therefore are fine to just import the
 // symbols required.
 import { core } from "./core";
-import { immutableDefine } from "./util";
 
 // During the build process, augmentations to the variable `window` in this
 // file are tracked and created as part of default library that is built into
@@ -71,7 +70,7 @@ window.window = window;
 // This is the Deno namespace, it is handled differently from other window
 // properties when building the runtime type library, as the whole module
 // is flattened into a single namespace.
-immutableDefine(window, "Deno", deno);
+window.Deno = deno;
 Object.freeze(window.Deno);
 
 // Globally available functions and object instances.

js/main.ts

@@ -18,8 +18,11 @@ import { setLocation } from "./location";
 // builtin modules
 import * as deno from "./deno";
 
-export default function denoMain(name?: string): void {
-  const startResMsg = os.start(name);
+export default function denoMain(
+  preserveDenoNamespace: boolean = true,
+  name?: string
+): void {
+  const startResMsg = os.start(preserveDenoNamespace, name);
 
   setVersions(startResMsg.denoVersion()!, startResMsg.v8Version()!);
 

js/os.ts

@@ -112,7 +112,10 @@ function sendStart(): msg.StartRes {
 // This function bootstraps an environment within Deno, it is shared both by
 // the runtime and the compiler environments.
 // @internal
-export function start(source?: string): msg.StartRes {
+export function start(
+  preserveDenoNamespace = true,
+  source?: string
+): msg.StartRes {
   core.setAsyncHandler(handleAsyncMsgFromRust);
 
   // First we send an empty `Start` message to let the privileged side know we
@@ -124,9 +127,18 @@ export function start(source?: string): msg.StartRes {
 
   setGlobals(startResMsg.pid(), startResMsg.noColor(), startResMsg.execPath()!);
 
-  // Deno.core could ONLY be safely frozen here (not in globals.ts)
-  // since shared_queue.js will modify core properties.
-  Object.freeze(window.Deno.core);
+  if (preserveDenoNamespace) {
+    util.immutableDefine(window, "Deno", window.Deno);
+    // Deno.core could ONLY be safely frozen here (not in globals.ts)
+    // since shared_queue.js will modify core properties.
+    Object.freeze(window.Deno.core);
+    // core.sharedQueue is an object so we should also freeze it.
+    Object.freeze(window.Deno.core.sharedQueue);
+  } else {
+    // Remove window.Deno
+    delete window.Deno;
+    assert(window.Deno === undefined);
+  }
 
   return startResMsg;
 }

js/workers.ts

@@ -20,10 +20,17 @@ export function decodeMessage(dataIntArray: Uint8Array): any {
   return JSON.parse(dataJson);
 }
 
-function createWorker(specifier: string): number {
+function createWorker(
+  specifier: string,
+  includeDenoNamespace: boolean
+): number {
   const builder = flatbuffers.createBuilder();
   const specifier_ = builder.createString(specifier);
-  const inner = msg.CreateWorker.createCreateWorker(builder, specifier_);
+  const inner = msg.CreateWorker.createCreateWorker(
+    builder,
+    specifier_,
+    includeDenoNamespace
+  );
   const baseRes = sendSync(builder, msg.Any.CreateWorker, inner);
   assert(baseRes != null);
   assert(
@@ -149,6 +156,18 @@ export interface Worker {
   closed: Promise<void>;
 }
 
+// TODO(kevinkassimo): Maybe implement reasonable web worker options?
+// eslint-disable-next-line @typescript-eslint/no-empty-interface
+export interface WorkerOptions {}
+
+/** Extended Deno Worker initialization options.
+ * `noDenoNamespace` hides global `window.Deno` namespace for
+ * spawned worker and nested workers spawned by it (default: false).
+ */
+export interface DenoWorkerOptions extends WorkerOptions {
+  noDenoNamespace?: boolean;
+}
+
 export class WorkerImpl implements Worker {
   private readonly rid: number;
   private isClosing: boolean = false;
@@ -157,8 +176,12 @@ export class WorkerImpl implements Worker {
   public onmessage?: (data: any) => void;
   public onmessageerror?: () => void;
 
-  constructor(specifier: string) {
-    this.rid = createWorker(specifier);
+  constructor(specifier: string, options?: DenoWorkerOptions) {
+    let includeDenoNamespace = true;
+    if (options && options.noDenoNamespace) {
+      includeDenoNamespace = false;
+    }
+    this.rid = createWorker(specifier, includeDenoNamespace);
     this.run();
     this.isClosedPromise = hostGetWorkerClosed(this.rid);
     this.isClosedPromise.then(