add method for printing found chrome path

bin/print-chrome-path.js

@@ -0,0 +1,16 @@
+#!/usr/bin/env node
+
+/**
+ * @license 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.
+ */
+'use strict';
+
+/** @fileoverview Prints the Chrome path that chrome-launcher will use. */
+
+const {getChromePath} = require('../dist/chrome-launcher.js');
+
+const chromePath = getChromePath();
+process.stdout.write(chromePath);
+process.exit(0);

package.json

@@ -13,6 +13,9 @@
     "type-check": "tsc --allowJs --checkJs --noEmit --target es2019 *.js",
     "prepublishOnly": "npm run build && npm run test"
   },
+  "bin": {
+    "print-chrome-path": "bin/print-chrome-path.js"
+  },
   "devDependencies": {
     "@types/mocha": "^8.0.4",
     "@types/sinon": "^9.0.1",

src/chrome-launcher.ts

@@ -84,6 +84,15 @@ async function launch(opts: Options = {}): Promise<LaunchedChrome> {
   return {pid: instance.pid!, port: instance.port!, kill, process: instance.chrome!};
 }
 
+/** Returns Chrome installation path that chrome-launcher will launch by default. */
+function getChromePath(): string {
+  const installation = Launcher.getFirstInstallation();
+  if (!installation) {
+    throw new ChromeNotInstalledError();
+  }
+  return installation;
+}
+
 async function killAll(): Promise<Array<Error>> {
   let errors = [];
   for (const instance of instances) {
@@ -420,4 +429,4 @@ class Launcher {
 };
 
 export default Launcher;
-export {Launcher, launch, killAll};
+export {Launcher, launch, killAll, getChromePath};

test/chrome-launcher-test.ts

@@ -5,7 +5,7 @@
  */
 'use strict';
 
-import {Launcher, launch, killAll, Options} from '../src/chrome-launcher';
+import {Launcher, launch, killAll, Options, getChromePath} from '../src/chrome-launcher';
 import {DEFAULT_FLAGS} from '../src/flags';
 
 import {spy, stub} from 'sinon';
@@ -217,4 +217,14 @@ describe('Launcher', () => {
     const chromeInstance = new Launcher({chromePath: ''});
     chromeInstance.launch().catch(() => done());
   });
+
+  describe('getChromePath', async () => {
+    it('returns the same path as a full Launcher launch', async () => {
+      const spawnStub = await launchChromeWithOpts();
+      const launchedPath = spawnStub.getCall(0).args[0] as string;
+
+      const chromePath = getChromePath();
+      assert.strictEqual(chromePath, launchedPath);
+    });
+  });
 });