chore(workers): align worker lifecycle evens with other APIs (#1147)

docs/api.md

@@ -481,8 +481,7 @@ page.removeListener('request', logRequest);
 - [event: 'requestfailed'](#event-requestfailed)
 - [event: 'requestfinished'](#event-requestfinished)
 - [event: 'response'](#event-response)
-- [event: 'workercreated'](#event-workercreated)
+- [event: 'worker'](#event-worker)
-- [event: 'workerdestroyed'](#event-workerdestroyed)
 - [page.$(selector)](#pageselector)
 - [page.$$(selector)](#pageselector-1)
 - [page.$$eval(selector, pageFunction[, ...args])](#pageevalselector-pagefunction-args)
@@ -653,16 +652,11 @@ Emitted when a request finishes successfully.
 
 Emitted when a [response] is received.
 
-#### event: 'workercreated'
+#### event: 'worker'
 - <[Worker]>
 
 Emitted when a dedicated [WebWorker](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API) is spawned by the page.
 
-#### event: 'workerdestroyed'
-- <[Worker]>
-
-Emitted when a dedicated [WebWorker](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API) is terminated.
-
 #### page.$(selector)
 - `selector` <[string]> A selector to query page for
 - returns: <[Promise]<?[ElementHandle]>>
@@ -3272,11 +3266,14 @@ function findFocusedNode(node) {
 ### class: Worker
 
 The Worker class represents a [WebWorker](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API).
-The events `workercreated` and `workerdestroyed` are emitted on the page object to signal the worker lifecycle.
+`worker` event is emitted on the page object to signal a worker creation.
+`close` event is emitted on the worker object when the worker is gone.
 
 ```js
-page.on('workercreated', worker => console.log('Worker created: ' + worker.url()));
+page.on('worker', worker => {
-page.on('workerdestroyed', worker => console.log('Worker destroyed: ' + worker.url()));
+  console.log('Worker created: ' + worker.url());
+  worker.on('close', worker => console.log('Worker destroyed: ' + worker.url()));
+});
 
 console.log('Current workers:');
 for (const worker of page.workers())
@@ -3284,11 +3281,17 @@ for (const worker of page.workers())
 ```
 
 <!-- GEN:toc -->
+- [event: 'close'](#event-close-2)
 - [worker.evaluate(pageFunction[, ...args])](#workerevaluatepagefunction-args)
 - [worker.evaluateHandle(pageFunction[, ...args])](#workerevaluatehandlepagefunction-args)
 - [worker.url()](#workerurl)
 <!-- GEN:stop -->
 
+#### event: 'close'
+- <[Worker]>
+
+Emitted when this dedicated [WebWorker](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API) is terminated.
+
 #### worker.evaluate(pageFunction[, ...args])
 - `pageFunction` <[function]|[string]> Function to be evaluated in the worker context
 - `...args` <...[Serializable]|[JSHandle]> Arguments to pass to `pageFunction`
@@ -3314,7 +3317,7 @@ If the function passed to the `worker.evaluateHandle` returns a [Promise], then
 ### class: BrowserServer
 
 <!-- GEN:toc -->
-- [event: 'close'](#event-close-2)
+- [event: 'close'](#event-close-3)
 - [browserServer.close()](#browserserverclose)
 - [browserServer.kill()](#browserserverkill)
 - [browserServer.process()](#browserserverprocess)

src/events.ts

@@ -46,7 +46,10 @@ export const Events = {
     FrameNavigated: 'framenavigated',
     Load: 'load',
     Popup: 'popup',
-    WorkerCreated: 'workercreated',
+    Worker: 'worker',
-    WorkerDestroyed: 'workerdestroyed',
+  },
+
+  Worker: {
+    Close: 'close',
   },
 };

src/page.ts

@@ -534,20 +534,20 @@ export class Page extends platform.EventEmitter {
 
   _addWorker(workerId: string, worker: Worker) {
     this._workers.set(workerId, worker);
-    this.emit(Events.Page.WorkerCreated, worker);
+    this.emit(Events.Page.Worker, worker);
   }
 
   _removeWorker(workerId: string) {
     const worker = this._workers.get(workerId);
     if (!worker)
       return;
-    this.emit(Events.Page.WorkerDestroyed, worker);
+    worker.emit(Events.Worker.Close, worker);
     this._workers.delete(workerId);
   }
 
   _clearWorkers() {
     for (const [workerId, worker] of this._workers) {
-      this.emit(Events.Page.WorkerDestroyed, worker);
+      worker.emit(Events.Worker.Close, worker);
       this._workers.delete(workerId);
     }
   }
@@ -569,13 +569,14 @@ export class Page extends platform.EventEmitter {
   }
 }
 
-export class Worker {
+export class Worker extends platform.EventEmitter {
   private _url: string;
   private _executionContextPromise: Promise<js.ExecutionContext>;
   private _executionContextCallback: (value?: js.ExecutionContext) => void;
   _existingExecutionContext: js.ExecutionContext | null = null;
 
   constructor(url: string) {
+    super();
     this._url = url;
     this._executionContextCallback = () => {};
     this._executionContextPromise = new Promise(x => this._executionContextCallback = x);

test/workers.spec.js

@@ -29,7 +29,7 @@ module.exports.describe = function({testRunner, expect, FFOX, CHROMIUM, WEBKIT})
   describe('Workers', function() {
     it('Page.workers', async function({page, server}) {
       await Promise.all([
-        page.waitForEvent('workercreated'),
+        page.waitForEvent('worker'),
         page.goto(server.PREFIX + '/worker/worker.html')]);
       const worker = page.workers()[0];
       expect(worker.url()).toContain('worker.js');
@@ -40,11 +40,11 @@ module.exports.describe = function({testRunner, expect, FFOX, CHROMIUM, WEBKIT})
       expect(page.workers().length).toBe(0);
     });
     it('should emit created and destroyed events', async function({page}) {
-      const workerCreatedPromise = page.waitForEvent('workercreated');
+      const workerCreatedPromise = page.waitForEvent('worker');
       const workerObj = await page.evaluateHandle(() => new Worker(URL.createObjectURL(new Blob(['1'], {type: 'application/javascript'}))));
       const worker = await workerCreatedPromise;
       const workerThisObj = await worker.evaluateHandle(() => this);
-      const workerDestroyedPromise = new Promise(x => page.once('workerdestroyed', x));
+      const workerDestroyedPromise = new Promise(x => worker.once('close', x));
       await page.evaluate(workerObj => workerObj.terminate(), workerObj);
       expect(await workerDestroyedPromise).toBe(worker);
       const error = await workerThisObj.getProperty('self').catch(error => error);
@@ -66,7 +66,7 @@ module.exports.describe = function({testRunner, expect, FFOX, CHROMIUM, WEBKIT})
       expect(await (await log.args()[3].getProperty('origin')).jsonValue()).toBe('null');
     });
     it('should evaluate', async function({page}) {
-      const workerCreatedPromise = page.waitForEvent('workercreated');
+      const workerCreatedPromise = page.waitForEvent('worker');
       page.evaluate(() => new Worker(URL.createObjectURL(new Blob(['console.log(1)'], {type: 'application/javascript'}))));
       const worker = await workerCreatedPromise;
       expect(await worker.evaluate('1+1')).toBe(2);
@@ -79,31 +79,31 @@ module.exports.describe = function({testRunner, expect, FFOX, CHROMIUM, WEBKIT})
     });
     it('should clear upon navigation', async function({server, page}) {
       await page.goto(server.EMPTY_PAGE);
-      const workerCreatedPromise = page.waitForEvent('workercreated');
+      const workerCreatedPromise = page.waitForEvent('worker');
       page.evaluate(() => new Worker(URL.createObjectURL(new Blob(['console.log(1)'], {type: 'application/javascript'}))));
-      await workerCreatedPromise;
+      const worker = await workerCreatedPromise;
       expect(page.workers().length).toBe(1);
       let destroyed = false;
-      page.once('workerdestroyed', () => destroyed = true);
+      worker.once('close', () => destroyed = true);
       await page.goto(server.PREFIX + '/one-style.html');
       expect(destroyed).toBe(true);
       expect(page.workers().length).toBe(0);
     });
     it('should clear upon cross-process navigation', async function({server, page}) {
       await page.goto(server.EMPTY_PAGE);
-      const workerCreatedPromise = page.waitForEvent('workercreated');
+      const workerCreatedPromise = page.waitForEvent('worker');
       page.evaluate(() => new Worker(URL.createObjectURL(new Blob(['console.log(1)'], {type: 'application/javascript'}))));
-      await workerCreatedPromise;
+      const worker = await workerCreatedPromise;
       expect(page.workers().length).toBe(1);
       let destroyed = false;
-      page.once('workerdestroyed', () => destroyed = true);
+      worker.once('close', () => destroyed = true);
       await page.goto(server.CROSS_PROCESS_PREFIX + '/empty.html');
       expect(destroyed).toBe(true);
       expect(page.workers().length).toBe(0);
     });
     it('should report network activity', async function({page, server}) {
       const [worker] = await Promise.all([
-        page.waitForEvent('workercreated'),
+        page.waitForEvent('worker'),
         page.goto(server.PREFIX + '/worker/worker.html'),
       ]);
       const url = server.PREFIX + '/one-style.css';
@@ -133,7 +133,7 @@ module.exports.describe = function({testRunner, expect, FFOX, CHROMIUM, WEBKIT})
     });
     false && it.skip(FFOX)('should report web socket activity', async function({page, server}) {
       const [worker] = await Promise.all([
-        page.waitForEvent('workercreated'),
+        page.waitForEvent('worker'),
         page.goto(server.PREFIX + '/worker/worker.html'),
       ]);
       const log = [];