support nested worker when running without iframe

src/vs/workbench/services/extensions/browser/webWorkerExtensionHost.ts

@@ -30,6 +30,7 @@ import { canceled, onUnexpectedError } from 'vs/base/common/errors';
 import { Barrier } from 'vs/base/common/async';
 import { FileAccess } from 'vs/base/common/network';
 import { ILayoutService } from 'vs/platform/layout/browser/layoutService';
+import { NewWorkerMessage, TerminateWorkerMessage } from 'vs/workbench/services/extensions/common/polyfillNestedWorker.protocol';
 
 export interface IWebWorkerExtensionHostInitData {
 	readonly autoStart: boolean;
@@ -224,15 +225,42 @@ export class WebWorkerExtensionHost extends Disposable implements IExtensionHost
 		const barrier = new Barrier();
 		let port!: MessagePort;
 
+		const nestedWorker = new Map<string, Worker>();
+
 		worker.onmessage = (event) => {
-			const { data } = event;
-			if (barrier.isOpen() || !(data instanceof MessagePort)) {
+
+			const data: MessagePort | NewWorkerMessage | TerminateWorkerMessage = event.data;
+
+			if (data instanceof MessagePort) {
+				// receiving a message port which is used to communicate
+				// with the web worker extension host
+				if (barrier.isOpen()) {
+					console.warn('UNEXPECTED message', event);
+					this._onDidExit.fire([ExtensionHostExitCode.UnexpectedError, 'received a message port AFTER opening the barrier']);
+					return;
+				}
+				port = data;
+				barrier.open();
+
+
+			} else if (data?.type === '_newWorker') {
+				// receiving a message to create a new nested/child worker
+				const worker = new Worker(data.url, data.options);
+				worker.postMessage(data.port, [data.port]);
+				nestedWorker.set(data.id, worker);
+
+			} else if (data?.type === '_terminateWorker') {
+				// receiving a message to terminate nested/child worker
+				if (nestedWorker.has(data.id)) {
+					nestedWorker.get(data.id)!.terminate();
+					nestedWorker.delete(data.id);
+				}
+
+			} else {
+				// all other messages are an error
 				console.warn('UNEXPECTED message', event);
 				this._onDidExit.fire([ExtensionHostExitCode.UnexpectedError, 'UNEXPECTED message']);
-				return;
 			}
-			port = data;
-			barrier.open();
 		};
 
 		// await MessagePort and use it to directly communicate

src/vs/workbench/services/extensions/common/polyfillNestedWorker.protocol.ts

+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+
+export interface NewWorkerMessage {
+	type: '_newWorker';
+	id: string;
+	port: MessagePort;
+	url: string;
+	options: WorkerOptions | undefined
+}
+
+export interface TerminateWorkerMessage {
+	type: '_terminateWorker';
+	id: string;
+}

src/vs/workbench/services/extensions/worker/polyfillNestedWorker.ts

@@ -3,6 +3,7 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
+import { NewWorkerMessage, TerminateWorkerMessage } from 'vs/workbench/services/extensions/common/polyfillNestedWorker.protocol';
 
 declare function postMessage(data: any, transferables?: Transferable[]): void;
 
@@ -53,19 +54,6 @@ const _bootstrapFnSource = (function _bootstrapFn(workerUrl: string) {
 }).toString();
 
 
-interface NewWorkerMessage {
-	type: '_newWorker';
-	id: string;
-	port: MessagePort;
-	url: string;
-	options: WorkerOptions | undefined
-}
-
-interface TerminateWorkerMessage {
-	type: '_terminateWorker';
-	id: string;
-}
-
 export class NestedWorker extends EventTarget implements Worker {
 
 	onmessage: ((this: Worker, ev: MessageEvent<any>) => any) | null = null;