feat(firefox): allow passing user prefs at launch time (#2417)

docs/api.md

@@ -3997,6 +3997,7 @@ This methods attaches Playwright to an existing browser instance.
   - `executablePath` <[string]> Path to a browser executable to run instead of the bundled one. If `executablePath` is a relative path, then it is resolved relative to [current working directory](https://nodejs.org/api/process.html#process_process_cwd). Note that Playwright only works with the bundled Chromium, Firefox or WebKit, use at your own risk.
   - `args` <[Array]<[string]>> Additional arguments to pass to the browser instance. The list of Chromium flags can be found [here](http://peter.sh/experiments/chromium-command-line-switches/).
   - `ignoreDefaultArgs` <[boolean]|[Array]<[string]>> If `true`, Playwright does not pass its own configurations args and only uses the ones from `args`. If an array is given, then filters out the given default arguments. Dangerous option; use with care. Defaults to `false`.
+  - `firefoxUserPrefs` <[Object]> Firefox user preferences. Learn more about the Firefox user preferences at [`about:config`](https://support.mozilla.org/en-US/kb/about-config-editor-firefox).
   - `handleSIGINT` <[boolean]> Close the browser process on Ctrl-C. Defaults to `true`.
   - `handleSIGTERM` <[boolean]> Close the browser process on SIGTERM. Defaults to `true`.
   - `handleSIGHUP` <[boolean]> Close the browser process on SIGHUP. Defaults to `true`.
@@ -4072,6 +4073,7 @@ Launches browser that uses persistent storage located at `userDataDir` and retur
   - `executablePath` <[string]> Path to a browser executable to run instead of the bundled one. If `executablePath` is a relative path, then it is resolved relative to [current working directory](https://nodejs.org/api/process.html#process_process_cwd). **BEWARE**: Playwright is only guaranteed to work with the bundled Chromium, Firefox or WebKit, use at your own risk.
   - `args` <[Array]<[string]>> Additional arguments to pass to the browser instance. The list of Chromium flags can be found [here](http://peter.sh/experiments/chromium-command-line-switches/).
   - `ignoreDefaultArgs` <[boolean]|[Array]<[string]>> If `true`, then do not use any of the default arguments. If an array is given, then filter out the given default arguments. Dangerous option; use with care. Defaults to `false`.
+  - `firefoxUserPrefs` <[Object]> Firefox user preferences. Learn more about the Firefox user preferences at [`about:config`](https://support.mozilla.org/en-US/kb/about-config-editor-firefox).
   - `handleSIGINT` <[boolean]> Close the browser process on Ctrl-C. Defaults to `true`.
   - `handleSIGTERM` <[boolean]> Close the browser process on SIGTERM. Defaults to `true`.
   - `handleSIGHUP` <[boolean]> Close the browser process on SIGHUP. Defaults to `true`.

src/server/browserType.ts

@@ -36,6 +36,10 @@ export type BrowserArgOptions = {
   devtools?: boolean,
 };
 
+export type FirefoxUserPrefsOptions = {
+  firefoxUserPrefs?: { [key: string]: string | number | boolean },
+};
+
 type LaunchOptionsBase = BrowserArgOptions & {
   executablePath?: string,
   ignoreDefaultArgs?: boolean | string[],
@@ -64,8 +68,8 @@ type LaunchServerOptions = LaunchOptionsBase & { port?: number };
 export interface BrowserType {
   executablePath(): string;
   name(): string;
-  launch(options?: LaunchOptions): Promise<Browser>;
-  launchServer(options?: LaunchServerOptions): Promise<BrowserServer>;
+  launch(options?: LaunchOptions & FirefoxUserPrefsOptions): Promise<Browser>;
+  launchServer(options?: LaunchServerOptions & FirefoxUserPrefsOptions): Promise<BrowserServer>;
   launchPersistentContext(userDataDir: string, options?: LaunchOptions & PersistentContextOptions): Promise<BrowserContext>;
   connect(options: ConnectOptions): Promise<Browser>;
 }

src/server/firefox.ts

@@ -16,13 +16,14 @@
  */
 
 import * as os from 'os';
+import * as fs from 'fs';
 import * as path from 'path';
 import * as ws from 'ws';
 import { FFBrowser } from '../firefox/ffBrowser';
 import { kBrowserCloseMessageId } from '../firefox/ffConnection';
 import { helper } from '../helper';
 import { WebSocketWrapper } from './browserServer';
-import { BrowserArgOptions, BrowserTypeBase, processBrowserArgOptions } from './browserType';
+import { BrowserArgOptions, BrowserTypeBase, processBrowserArgOptions, FirefoxUserPrefsOptions } from './browserType';
 import { Env } from './processLauncher';
 import { ConnectionTransport, SequenceNumberMixer } from '../transport';
 import { InnerLogger, logError } from '../logger';
@@ -56,7 +57,7 @@ export class Firefox extends BrowserTypeBase {
     return wrapTransportWithWebSocket(transport, logger, port);
   }
 
-  _defaultArgs(options: BrowserArgOptions, isPersistent: boolean, userDataDir: string): string[] {
+  _defaultArgs(options: BrowserArgOptions & FirefoxUserPrefsOptions, isPersistent: boolean, userDataDir: string): string[] {
     const { devtools, headless } = processBrowserArgOptions(options);
     const { args = [] } = options;
     if (devtools)
@@ -66,7 +67,12 @@ export class Firefox extends BrowserTypeBase {
       throw new Error('Pass userDataDir parameter instead of specifying -profile argument');
     if (args.find(arg => arg.startsWith('-juggler')))
       throw new Error('Use the port parameter instead of -juggler argument');
-
+    if (options.firefoxUserPrefs) {
+      const lines: string[] = [];
+      for (const [name, value] of Object.entries(options.firefoxUserPrefs))
+        lines.push(`user_pref(${JSON.stringify(name)}, ${JSON.stringify(value)});`);
+      fs.writeFileSync(path.join(userDataDir, 'user.js'), lines.join('\n'));
+    }
     const firefoxArguments = ['-no-remote'];
     if (headless) {
       firefoxArguments.push('-headless');

test/firefox/launcher.spec.js

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * 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.
+ */
+
+const path = require('path');
+const utils = require('../utils');
+const {makeUserDataDir, removeUserDataDir} = utils;
+const {FFOX, CHROMIUM, WEBKIT, WIN} = utils.testOptions(browserType);
+
+describe('launcher', function() {
+  it('should pass firefox user preferences', async({browserType, defaultBrowserOptions}) => {
+    const browser = await browserType.launch({
+      ...defaultBrowserOptions,
+      firefoxUserPrefs: {
+        'network.proxy.type': 1,
+        'network.proxy.http': '127.0.0.1',
+        'network.proxy.http_port': 3333,
+      }
+    });
+    const page = await browser.newPage();
+    const error = await page.goto('http://example.com').catch(e => e);
+    expect(error.message).toContain('NS_ERROR_PROXY_CONNECTION_REFUSED');
+    await browser.close();
+  });
+});

test/test.config.js

@@ -243,6 +243,15 @@ module.exports = {
       environments: [customEnvironment],
     },
 
+    {
+      files: [
+        './firefox/launcher.spec.js',
+      ],
+      browsers: ['firefox'],
+      title: '[Firefox]',
+      environments: [customEnvironment],
+    },
+
     {
       files: [
         './electron/electron.spec.js',