feat: add page.emulateNetworkConditions (#6759)

docs/api.md

@@ -42,6 +42,7 @@
   * [puppeteer.errors](#puppeteererrors)
   * [puppeteer.executablePath()](#puppeteerexecutablepath)
   * [puppeteer.launch([options])](#puppeteerlaunchoptions)
+  * [puppeteer.networkConditions](#puppeteernetworkconditions)
   * [puppeteer.product](#puppeteerproduct)
   * [puppeteer.registerCustomQueryHandler(name, queryHandler)](#puppeteerregistercustomqueryhandlername-queryhandler)
   * [puppeteer.unregisterCustomQueryHandler(name)](#puppeteerunregistercustomqueryhandlername)
@@ -128,6 +129,7 @@
   * [page.emulateIdleState(overrides)](#pageemulateidlestateoverrides)
   * [page.emulateMediaFeatures(features)](#pageemulatemediafeaturesfeatures)
   * [page.emulateMediaType(type)](#pageemulatemediatypetype)
+  * [page.emulateNetworkConditions(networkConditions)](#pageemulatenetworkconditionsnetworkconditions)
   * [page.emulateTimezone(timezoneId)](#pageemulatetimezonetimezoneid)
   * [page.emulateVisionDeficiency(type)](#pageemulatevisiondeficiencytype)
   * [page.evaluate(pageFunction[, ...args])](#pageevaluatepagefunction-args)
@@ -610,6 +612,26 @@ const browser = await puppeteer.launch({
 >
 > See [`this article`](https://www.howtogeek.com/202825/what%E2%80%99s-the-difference-between-chromium-and-chrome/) for a description of the differences between Chromium and Chrome. [`This article`](https://chromium.googlesource.com/chromium/src/+/lkgr/docs/chromium_browser_vs_google_chrome.md) describes some differences for Linux users.
 
+#### puppeteer.networkConditions
+- returns: <[Object]>
+
+Returns a list of network conditions to be used with [`page.emulateNetworkConditions(networkConditions)`](#pageemulatenetworkconditionsnetworkconditions). Actual list of
+conditions can be found in [`src/common/NetworkConditions.ts`](https://github.com/puppeteer/puppeteer/blob/main/src/common/NetworkConditions.ts).
+
+```js
+const puppeteer = require('puppeteer');
+const slow3G = puppeteer.networkConditions['Slow 3G'];
+
+(async () => {
+  const browser = await puppeteer.launch();
+  const page = await browser.newPage();
+  await page.emulateNetworkConditions(slow3G);
+  await page.goto('https://www.google.com');
+  // other actions...
+  await browser.close();
+})();
+```
+
 #### puppeteer.product
 - returns: <[string]> returns the name of the browser that is under automation (`"chrome"` or `"firefox"`)
 
@@ -1441,6 +1463,29 @@ await page.evaluate(() => matchMedia('print').matches);
 // → false
 ```
 
+#### page.emulateNetworkConditions(networkConditions) 
+- `networkConditions` <?[Object]> Passing `null` disables network condition emulation.
+  - `download` <[number]> Download speed (bytes/s), `-1` to disable
+  - `upload` <[number]> Upload speed (bytes/s), `-1` to disable
+  - `latency` <[number]> Latency (ms), `0` to disable
+- returns: <[Promise]>
+
+> **NOTE** This does not affect WebSockets and WebRTC PeerConnections (see https://crbug.com/563644)
+
+```js
+const puppeteer = require('puppeteer');
+const slow3G = puppeteer.networkConditions['Slow 3G'];
+
+(async () => {
+  const browser = await puppeteer.launch();
+  const page = await browser.newPage();
+  await page.emulateNetworkConditions(slow3G);
+  await page.goto('https://www.google.com');
+  // other actions...
+  await browser.close();
+})();
+```
+
 #### page.emulateTimezone(timezoneId)
 - `timezoneId` <?[string]> Changes the timezone of the page. See [ICU’s `metaZones.txt`](https://cs.chromium.org/chromium/src/third_party/icu/source/data/misc/metaZones.txt?rcl=faee8bc70570192d82d2978a71e2a615788597d1) for a list of supported timezone IDs. Passing `null` disables timezone emulation.
 - returns: <[Promise]>

src/common/NetworkConditions.ts

@@ -0,0 +1,32 @@
+/**
+ * Copyright 2021 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { NetworkConditions } from './NetworkManager.js';
+
+export type PredefinedNetworkConditions = { [name: string]: NetworkConditions };
+
+export const networkConditions: PredefinedNetworkConditions = {
+  'Slow 3G': {
+    download: ((500 * 1000) / 8) * 0.8,
+    upload: ((500 * 1000) / 8) * 0.8,
+    latency: 400 * 5,
+  },
+  'Fast 3G': {
+    download: ((1.6 * 1000 * 1000) / 8) * 0.9,
+    upload: ((750 * 1000) / 8) * 0.9,
+    latency: 150 * 3.75,
+  },
+};

src/common/NetworkManager.ts

@@ -30,6 +30,22 @@ export interface Credentials {
   password: string;
 }
 
+/**
+ * @public
+ */
+export interface NetworkConditions {
+  // Download speed (bytes/s)
+  download: number;
+  // Upload speed (bytes/s)
+  upload: number;
+  // Latency (ms)
+  latency: number;
+}
+
+export interface InternalNetworkConditions extends NetworkConditions {
+  offline: boolean;
+}
+
 /**
  * We use symbols to prevent any external parties listening to these events.
  * They are internal to Puppeteer.
@@ -56,13 +72,18 @@ export class NetworkManager extends EventEmitter {
     Protocol.Network.RequestWillBeSentEvent
   >();
   _extraHTTPHeaders: Record<string, string> = {};
-  _offline = false;
   _credentials?: Credentials = null;
   _attemptedAuthentications = new Set<string>();
   _userRequestInterceptionEnabled = false;
   _protocolRequestInterceptionEnabled = false;
   _userCacheDisabled = false;
   _requestIdToInterceptionId = new Map<string, string>();
+  _emulatedNetworkConditions: InternalNetworkConditions = {
+    offline: false,
+    upload: -1,
+    download: -1,
+    latency: 0,
+  };
 
   constructor(
     client: CDPSession,
@@ -130,14 +151,32 @@ export class NetworkManager extends EventEmitter {
   }
 
   async setOfflineMode(value: boolean): Promise<void> {
-    if (this._offline === value) return;
-    this._offline = value;
+    this._emulatedNetworkConditions.offline = value;
+    await this._updateNetworkConditions();
+  }
+
+  async emulateNetworkConditions(
+    networkConditions: NetworkConditions | null
+  ): Promise<void> {
+    this._emulatedNetworkConditions.upload = networkConditions
+      ? networkConditions.upload
+      : -1;
+    this._emulatedNetworkConditions.download = networkConditions
+      ? networkConditions.download
+      : -1;
+    this._emulatedNetworkConditions.latency = networkConditions
+      ? networkConditions.latency
+      : 0;
+
+    await this._updateNetworkConditions();
+  }
+
+  async _updateNetworkConditions(): Promise<void> {
     await this._client.send('Network.emulateNetworkConditions', {
-      offline: this._offline,
-      // values of 0 remove any active throttling. crbug.com/456324#c9
-      latency: 0,
-      downloadThroughput: -1,
-      uploadThroughput: -1,
+      offline: this._emulatedNetworkConditions.offline,
+      latency: this._emulatedNetworkConditions.latency,
+      uploadThroughput: this._emulatedNetworkConditions.upload,
+      downloadThroughput: this._emulatedNetworkConditions.download,
     });
   }
 

src/common/Page.ts

@@ -37,7 +37,11 @@ import { Browser, BrowserContext } from './Browser.js';
 import { Target } from './Target.js';
 import { createJSHandle, JSHandle, ElementHandle } from './JSHandle.js';
 import { Viewport } from './PuppeteerViewport.js';
-import { Credentials, NetworkManagerEmittedEvents } from './NetworkManager.js';
+import {
+  Credentials,
+  NetworkConditions,
+  NetworkManagerEmittedEvents,
+} from './NetworkManager.js';
 import { HTTPRequest } from './HTTPRequest.js';
 import { HTTPResponse } from './HTTPResponse.js';
 import { Accessibility } from './Accessibility.js';
@@ -693,6 +697,14 @@ export class Page extends EventEmitter {
     return this._frameManager.networkManager().setOfflineMode(enabled);
   }
 
+  emulateNetworkConditions(
+    networkConditions: NetworkConditions | null
+  ): Promise<void> {
+    return this._frameManager
+      .networkManager()
+      .emulateNetworkConditions(networkConditions);
+  }
+
   /**
    * @param timeout - Maximum navigation time in milliseconds.
    */

src/common/Puppeteer.ts

@@ -26,6 +26,10 @@ import {
 } from './QueryHandler.js';
 import { Product } from './Product.js';
 import { connectToBrowser, BrowserOptions } from './BrowserConnector.js';
+import {
+  PredefinedNetworkConditions,
+  networkConditions,
+} from './NetworkConditions.js';
 
 /**
  * Settings that are common to the Puppeteer class, regardless of enviroment.
@@ -125,6 +129,31 @@ export class Puppeteer {
     return puppeteerErrors;
   }
 
+  /**
+   * @remarks
+   * Returns a list of network conditions to be used with `page.emulateNetworkConditions(networkConditions)`. Actual list of predefined conditions can be found in {@link https://github.com/puppeteer/puppeteer/blob/main/src/common/NetworkConditions.ts | src/common/NetworkConditions.ts}.
+   *
+   * @example
+   *
+   * ```js
+   * const puppeteer = require('puppeteer');
+   * const slow3G = puppeteer.networkConditions['Slow 3G'];
+   *
+   * (async () => {
+   *   const browser = await puppeteer.launch();
+   *   const page = await browser.newPage();
+   *   await page.emulateNetworkConditions(slow3G);
+   *   await page.goto('https://www.google.com');
+   *   // other actions...
+   *   await browser.close();
+   * })();
+   * ```
+   *
+   */
+  get networkConditions(): PredefinedNetworkConditions {
+    return networkConditions;
+  }
+
   /**
    * Registers a {@link CustomQueryHandler | custom query handler}. After
    * registration, the handler can be used everywhere where a selector is

test/page.spec.ts

@@ -388,6 +388,28 @@ describe('Page', function () {
     });
   });
 
+  describeFailsFirefox('Page.emulateNetworkConditions', function () {
+    it('should change navigator.connection.effectiveType', async () => {
+      const { page, puppeteer } = getTestState();
+
+      const slow3G = puppeteer.networkConditions['Slow 3G'];
+      const fast3G = puppeteer.networkConditions['Fast 3G'];
+
+      expect(
+        await page.evaluate('window.navigator.connection.effectiveType')
+      ).toBe('4g');
+      await page.emulateNetworkConditions(fast3G);
+      expect(
+        await page.evaluate('window.navigator.connection.effectiveType')
+      ).toBe('3g');
+      await page.emulateNetworkConditions(slow3G);
+      expect(
+        await page.evaluate('window.navigator.connection.effectiveType')
+      ).toBe('2g');
+      await page.emulateNetworkConditions(null);
+    });
+  });
+
   describe('ExecutionContext.queryObjects', function () {
     itFailsFirefox('should work', async () => {
       const { page } = getTestState();

utils/doclint/check_public_api/index.js

@@ -576,6 +576,13 @@ function compareDocumentations(actual, expected) {
           expectedName: 'Viewport',
         },
       ],
+      [
+        'Method Page.emulateNetworkConditions() networkConditions',
+        {
+          actualName: 'Object',
+          expectedName: 'NetworkConditions',
+        },
+      ],
       [
         'Method Page.setViewport() options.viewport',
         {