feat: make node-notifier an optional dependency

packages/jest-reporters/package.json

@@ -23,7 +23,6 @@
     "jest-runtime": "^24.9.0",
     "jest-util": "^24.9.0",
     "jest-worker": "^24.6.0",
-    "node-notifier": "^5.4.3",
     "slash": "^3.0.0",
     "source-map": "^0.6.0",
     "string-length": "^3.1.0"
@@ -39,6 +38,9 @@
     "@types/node-notifier": "^5.4.0",
     "strip-ansi": "^5.0.0"
   },
+  "optionalDependencies": {
+    "node-notifier": "^5.4.3"
+  },
   "engines": {
     "node": ">= 8"
   },

packages/jest-reporters/src/__tests__/notify_impl.test.ts

@@ -0,0 +1,41 @@
+beforeEach(() => {
+  jest.resetModules();
+});
+
+test('without node-notifier notify_impl uses mock function that throws an error', () => {
+  jest.doMock('node-notifier', () => {
+    const error: any = new Error("Cannot find module 'node-notifier'");
+    error.code = 'MODULE_NOT_FOUND';
+    throw error;
+  });
+  const notify = require('../notify_impl').default;
+  const arg = jest.fn();
+  expect(() => notify(arg)).toThrow(
+    'notify reporter requires optional dependeny node-notifier but it was not found',
+  );
+});
+
+test('notify_impl throws the error when require throws an unexpected error', () => {
+  const error = new Error('unexpected require error');
+  jest.doMock('node-notifier', () => {
+    throw error;
+  });
+  expect(() => require('../notify_impl')).toThrow(error);
+});
+
+test('notify_impl uses node-notifier when it is available', () => {
+  const mockNodeNotifier = {notify: jest.fn()};
+  jest.doMock('node-notifier', () => mockNodeNotifier);
+  const notify = require('../notify_impl').default;
+  // notify would be object equal to mockNodeNotifier.notify except we had
+  // to bind it to mockNodeNotifier, which returns a new function. so
+  // instead of expect(notify).toBe(mockNodeNotifier.notify) we need to
+  // check that the arguments and return values are forwarded, and that
+  // `this` is set to the module.
+  const arg = jest.fn();
+  const result = notify(arg);
+  expect(mockNodeNotifier.notify).toBeCalledTimes(1);
+  expect(mockNodeNotifier.notify).toBeCalledWith(arg);
+  expect(mockNodeNotifier.notify).toReturnWith(result);
+  expect(mockNodeNotifier.notify.mock.instances[0]).toEqual(mockNodeNotifier);
+});

packages/jest-reporters/src/notify_impl.ts

@@ -0,0 +1,52 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+export default getNotifier();
+
+/**
+ * Return a notifier implementation.
+ *
+ * node-notifier is an optional dependency so it may not be installed.
+ * If node-notifier is not found then a stub notifier is returned that throws
+ * an error whenever it is used.
+ */
+function getNotifier(): Notify {
+  try {
+    const notifier: typeof import('node-notifier') = require('node-notifier');
+    return notifier.notify.bind(notifier);
+  } catch (ex) {
+    if (ex.code !== 'MODULE_NOT_FOUND') {
+      throw ex;
+    }
+    return () => {
+      throw Error(
+        'notify reporter requires optional dependeny node-notifier but it was not found',
+      );
+    };
+  }
+}
+
+export type Notify = (
+  notification?: Notification,
+  callback?: NotificationCallback,
+) => unknown;
+
+interface Notification {
+  title?: string;
+  message?: string;
+  icon?: string;
+  closeLabel?: string;
+  actions?: string | Array<string>;
+  timeout?: number;
+}
+
+interface NotificationCallback {
+  (err: Error | null, response: string, metadata?: NotificationMetadata): void;
+}
+
+interface NotificationMetadata {
+  activationValue?: string;
+}

packages/jest-reporters/src/notify_reporter.ts

@@ -10,9 +10,9 @@ import * as util from 'util';
 import exit = require('exit');
 import {Config} from '@jest/types';
 import {AggregatedResult} from '@jest/test-result';
-import {notify} from 'node-notifier';
 import {Context, TestSchedulerContext} from './types';
 import BaseReporter from './base_reporter';
+import notify from './notify_impl';
 
 const isDarwin = process.platform === 'darwin';