Add module mock for DefaultToolLauncher and apply in tests (#55728)

Summary:
Pull Request resolved: #55728

Fixes unwanted side effect launches of the debugger shell in tests (likely introduced in D88161573!).

Also adds error guard on `DefaultAppLauncher` to ensure that the implementation is always mocked.

Changelog: [Internal]

Reviewed By: vzaidman

Differential Revision: D94230761

fbshipit-source-id: 966f6f09c38aa55594091bd7d34a5c78dc6eee93

Author: huntie

packages/dev-middleware/src/__tests__/InspectorProxyHttpApi-test.js

@@ -12,8 +12,8 @@ import type {
   JsonPagesListResponse,
   JsonVersionResponse,
 } from '../inspector-proxy/types';
+import type {DevToolLauncher} from '../types/DevToolLauncher';
 
-import DefaultToolLauncher from '../utils/DefaultToolLauncher';
 import {fetchJson, requestLocal} from './FetchUtils';
 import {createDeviceMock} from './InspectorDeviceUtils';
 import {withAbortSignalForEachTest} from './ResourceUtils';
@@ -24,12 +24,19 @@ const PAGES_POLLING_DELAY = 2100;
 
 jest.useFakeTimers();
 
+const mockDevToolLauncher: DevToolLauncher = {
+  launchDebuggerAppWindow: jest
+    .fn<[string], Promise<void>>()
+    .mockImplementation(() => Promise.resolve()),
+};
+
 describe('inspector proxy HTTP API', () => {
   const serverRef = withServerForEachTest({
     logger: undefined,
     unstable_experiments: {
       enableStandaloneFuseboxShell: false,
     },
+    unstable_toolLauncher: mockDevToolLauncher,
   });
   const autoCleanup = withAbortSignalForEachTest();
   afterEach(() => {
@@ -397,11 +404,6 @@ describe('inspector proxy HTTP API', () => {
       ]);
       jest.advanceTimersByTime(PAGES_POLLING_DELAY);
 
-      // Hook into `DefaultToolLauncher.launchDebuggerAppWindow` to ensure debugger was launched
-      const launchDebuggerSpy = jest
-        .spyOn(DefaultToolLauncher, 'launchDebuggerAppWindow')
-        .mockResolvedValueOnce();
-
       try {
         // Fetch the target information for the device
         const pageListResponse = await fetchJson<JsonPagesListResponse>(
@@ -426,7 +428,9 @@ describe('inspector proxy HTTP API', () => {
         // Ensure the request was handled properly
         expect(response.statusCode).toBe(200);
         // Ensure the debugger was launched
-        expect(launchDebuggerSpy).toHaveBeenCalledWith(expect.any(String));
+        expect(
+          mockDevToolLauncher.launchDebuggerAppWindow,
+        ).toHaveBeenCalledWith(expect.any(String));
       } finally {
         device.close();
       }

packages/dev-middleware/src/__tests__/ServerUtils.js

@@ -24,6 +24,8 @@ type CreateServerOptions = {
 };
 type ConnectApp = ReturnType<typeof connect>;
 
+jest.mock('../utils/DefaultToolLauncher');
+
 export function withServerForEachTest(options: CreateServerOptions): Readonly<{
   serverBaseUrl: string,
   serverBaseWsUrl: string,

packages/dev-middleware/src/__tests__/StandaloneFuseboxShell-test.js

@@ -11,7 +11,6 @@
 import type {JsonPagesListResponse} from '../inspector-proxy/types';
 import type {DevToolLauncher} from '../types/DevToolLauncher';
 
-import DefaultToolLauncher from '../utils/DefaultToolLauncher';
 import {fetchJson, requestLocal} from './FetchUtils';
 import {createDeviceMock} from './InspectorDeviceUtils';
 import {withAbortSignalForEachTest} from './ResourceUtils';
@@ -24,7 +23,7 @@ jest.useFakeTimers();
 
 describe('enableStandaloneFuseboxShell experiment', () => {
   const ToolLauncherWithFuseboxShell: DevToolLauncher = {
-    ...DefaultToolLauncher,
+    launchDebuggerAppWindow: async (url: string) => {},
     launchDebuggerShell: () => {
       throw new Error('Not implemented');
     },

packages/dev-middleware/src/utils/DefaultToolLauncher.js

@@ -25,6 +25,10 @@ const open = require('open');
  */
 const DefaultToolLauncher = {
   launchDebuggerAppWindow: async (url: string): Promise<void> => {
+    if (process.env.NODE_ENV === 'test') {
+      assertMockedInTests();
+    }
+
     let chromePath;
 
     try {
@@ -66,6 +70,10 @@ const DefaultToolLauncher = {
   },
 
   async launchDebuggerShell(url: string, windowKey: string): Promise<void> {
+    if (process.env.NODE_ENV === 'test') {
+      assertMockedInTests();
+    }
+
     return await unstable_spawnDebuggerShellWithArgs([
       '--frontendUrl=' + url,
       '--windowKey=' + windowKey,
@@ -75,8 +83,21 @@ const DefaultToolLauncher = {
   async prepareDebuggerShell(
     prebuiltBinaryPath?: ?string,
   ): Promise<DebuggerShellPreparationResult> {
+    if (process.env.NODE_ENV === 'test') {
+      assertMockedInTests();
+    }
+
     return await unstable_prepareDebuggerShell();
   },
 };
 
+function assertMockedInTests(): void {
+  if (process.env.NODE_ENV === 'test') {
+    throw new Error(
+      'DefaultToolLauncher must be mocked or overridden in tests. ' +
+        "Add jest.mock('../utils/DefaultAppLauncher') to test setup.",
+    );
+  }
+}
+
 export default DefaultToolLauncher;

packages/dev-middleware/src/utils/__mocks__/DefaultToolLauncher.js

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @noflow
+ * @format
+ */
+
+/**
+ * Mock implementation of DefaultToolLauncher to prevent actual browser
+ * and debugger-shell launches during tests.
+ */
+const DefaultToolLauncher = {
+  launchDebuggerAppWindow: jest
+    .fn()
+    .mockImplementation(() => Promise.resolve()),
+  launchDebuggerShell: jest.fn().mockImplementation(() => Promise.resolve()),
+  prepareDebuggerShell: jest.fn().mockResolvedValue({code: 'not_implemented'}),
+};
+
+export default DefaultToolLauncher;

private/react-native-fantom/runner/global-setup/globalSetup.js

@@ -8,6 +8,7 @@
  * @format
  */
 
+import type {DevToolLauncher} from '@react-native/dev-middleware';
 import type {ConfigT} from 'metro-config';
 
 import {isOSS, validateEnvironmentVariables} from '../EnvironmentOptions';
@@ -48,16 +49,19 @@ async function startMetroServer() {
   // $FlowExpectedError[cannot-write]
   metroConfig.server.port = Number(process.env.__FANTOM_METRO_PORT__);
 
+  // No-op app launcher to prevent debugger-shell launches during tests
+  const devToolLauncher: DevToolLauncher = {
+    launchDebuggerAppWindow: async (_url: string) => {},
+    launchDebuggerShell: async () => {},
+    prepareDebuggerShell: async () => ({code: 'not_implemented'}),
+  };
+
   const {
     middleware: devMiddleware,
     websocketEndpoints: debuggerWebsocketEndpoints,
   } = createDevMiddleware({
     serverBaseUrl: `http://localhost:${metroConfig.server.port}`,
-    // Disable standalone DevTools shell preparation to avoid launching the
-    // Electron app during tests. This prevents crashes.
-    unstable_experiments: {
-      enableStandaloneFuseboxShell: false,
-    },
+    unstable_toolLauncher: devToolLauncher,
   });
 
   const enhanceMiddleware: ConfigT['server']['enhanceMiddleware'] = (