feature(dev-middleware): add custom message handlers to extend CDP capabilities (#43291)

Summary:
This is a proposal for the `react-native/dev-middleware` package, to allow implementers to extend the CDP capabilities of the `InspectorProxy`. It's unfortunately needed until we can move to the native Hermes CDP layer.

At Expo, we extend the CDP capabilities of this `InspectorProxy` by injecting functionality on the device level. This proposed API does the same, but without having to overwrite internal functions of both the `InspectorProxy` and `InspectorDevice`.

A good example of this is the network inspector's capabilities. This currently works through the inspection proxy, and roughly like:
- Handle any incoming `Expo(Network.receivedResponseBody)` from the _**device**_, store it, and stop event from propagating
- Handle the incoming `Network.getResponseBody` from the _**debugger**_, return the data, and stop event from propagating.

This API brings back that capability in a more structured way.

## API:

```ts
import { createDevMiddleware } from 'react-native/dev-middleware';

const { middleware, websocketEndpoints } = createDevMiddleware({
  unstable_customInspectorMessageHandler: ({ page, deviceInfo, debuggerInfo }) => {
    // Do not enable handler for page other than "SOMETHING", or for vscode debugging
    // Can also include `page.capabilities` to determine if handler is required
    if (page.title !== 'SOMETHING' || debuggerInfo.userAgent?.includes('vscode')) {
      return null;
    }

    return {
      handleDeviceMessage(message) {
        if (message.type === 'CDP_MESSAGE') {
          // Do something and stop message from propagating with return `true`
          return true;
        }
      },
      handleDebuggerMessage(message) {
        if (message.type === 'CDP_MESSAGE') {
          // Do something and stop message from propagating with return `true`
          return true;
        }
      },
    };
  },
});
```

## Changelog:

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[GENERAL] [ADDED] - Add inspector proxy device message middleware API

Pull Request resolved: https://github.com/facebook/react-native/pull/43291

Test Plan: See added tests and code above

Reviewed By: huntie

Differential Revision: D54804503

Pulled By: motiz88

fbshipit-source-id: ae918dcd5b7e76d3fb31db4c84717567ae60fa96

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

@@ -0,0 +1,310 @@
+/**
+ * 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.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+import {createAndConnectTarget} from './InspectorProtocolUtils';
+import {withAbortSignalForEachTest} from './ResourceUtils';
+import {baseUrlForServer, createServer} from './ServerUtils';
+import until from 'wait-for-expect';
+
+// WebSocket is unreliable when using fake timers.
+jest.useRealTimers();
+
+jest.setTimeout(10000);
+
+describe('inspector proxy device message middleware', () => {
+  const autoCleanup = withAbortSignalForEachTest();
+  const page = {
+    id: 'page1',
+    app: 'bar-app',
+    title: 'bar-title',
+    vm: 'bar-vm',
+  };
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  test('middleware is created with device, debugger, and page information', async () => {
+    const createCustomMessageHandler = jest.fn().mockImplementation(() => null);
+    const {server} = await createServer({
+      logger: undefined,
+      projectRoot: '',
+      unstable_customInspectorMessageHandler: createCustomMessageHandler,
+    });
+
+    let device, debugger_;
+    try {
+      ({device, debugger_} = await createAndConnectTarget(
+        serverRefUrls(server),
+        autoCleanup.signal,
+        page,
+      ));
+
+      // Ensure the middleware was created with the device information
+      await until(() =>
+        expect(createCustomMessageHandler).toBeCalledWith(
+          expect.objectContaining({
+            page: expect.objectContaining({
+              ...page,
+              capabilities: expect.any(Object),
+            }),
+            device: expect.objectContaining({
+              appId: expect.any(String),
+              id: expect.any(String),
+              name: expect.any(String),
+              sendMessage: expect.any(Function),
+            }),
+            debugger: expect.objectContaining({
+              userAgent: null,
+              sendMessage: expect.any(Function),
+            }),
+          }),
+        ),
+      );
+    } finally {
+      device?.close();
+      debugger_?.close();
+      await closeServer(server);
+    }
+  });
+
+  test('send message functions are passing messages to sockets', async () => {
+    const handleDebuggerMessage = jest.fn();
+    const handleDeviceMessage = jest.fn();
+    const createCustomMessageHandler = jest.fn().mockImplementation(() => ({
+      handleDebuggerMessage,
+      handleDeviceMessage,
+    }));
+
+    const {server} = await createServer({
+      logger: undefined,
+      projectRoot: '',
+      unstable_customInspectorMessageHandler: createCustomMessageHandler,
+    });
+
+    let device, debugger_;
+    try {
+      ({device, debugger_} = await createAndConnectTarget(
+        serverRefUrls(server),
+        autoCleanup.signal,
+        page,
+      ));
+
+      // Ensure the middleware was created with the send message methods
+      await until(() =>
+        expect(createCustomMessageHandler).toBeCalledWith(
+          expect.objectContaining({
+            device: expect.objectContaining({
+              sendMessage: expect.any(Function),
+            }),
+            debugger: expect.objectContaining({
+              sendMessage: expect.any(Function),
+            }),
+          }),
+        ),
+      );
+
+      // Send a message to the device
+      createCustomMessageHandler.mock.calls[0][0].device.sendMessage({
+        id: 1,
+      });
+      // Ensure the device received the message
+      await until(() =>
+        expect(device.wrappedEvent).toBeCalledWith({
+          event: 'wrappedEvent',
+          payload: {
+            pageId: page.id,
+            wrappedEvent: JSON.stringify({id: 1}),
+          },
+        }),
+      );
+
+      // Send a message to the debugger
+      createCustomMessageHandler.mock.calls[0][0].debugger.sendMessage({
+        id: 2,
+      });
+      // Ensure the debugger received the message
+      await until(() =>
+        expect(debugger_.handle).toBeCalledWith({
+          id: 2,
+        }),
+      );
+    } finally {
+      device?.close();
+      debugger_?.close();
+      await closeServer(server);
+    }
+  });
+
+  test('device message is passed to message middleware', async () => {
+    const handleDeviceMessage = jest.fn();
+    const {server} = await createServer({
+      logger: undefined,
+      projectRoot: '',
+      unstable_customInspectorMessageHandler: () => ({
+        handleDeviceMessage,
+        handleDebuggerMessage() {},
+      }),
+    });
+
+    let device, debugger_;
+    try {
+      ({device, debugger_} = await createAndConnectTarget(
+        serverRefUrls(server),
+        autoCleanup.signal,
+        page,
+      ));
+
+      // Send a message from the device, and ensure the middleware received it
+      device.sendWrappedEvent(page.id, {id: 1337});
+
+      // Ensure the debugger received the message
+      await until(() => expect(debugger_.handle).toBeCalledWith({id: 1337}));
+      // Ensure the middleware received the message
+      await until(() => expect(handleDeviceMessage).toBeCalled());
+    } finally {
+      device?.close();
+      debugger_?.close();
+      await closeServer(server);
+    }
+  });
+
+  test('device message stops propagating when handled by middleware', async () => {
+    const handleDeviceMessage = jest.fn();
+    const {server} = await createServer({
+      logger: undefined,
+      projectRoot: '',
+      unstable_customInspectorMessageHandler: () => ({
+        handleDeviceMessage,
+        handleDebuggerMessage() {},
+      }),
+    });
+
+    let device, debugger_;
+    try {
+      ({device, debugger_} = await createAndConnectTarget(
+        serverRefUrls(server),
+        autoCleanup.signal,
+        page,
+      ));
+
+      // Stop the first message from propagating by returning true (once) from middleware
+      handleDeviceMessage.mockReturnValueOnce(true);
+
+      // Send the first message which should NOT be received by the debugger
+      device.sendWrappedEvent(page.id, {id: -1});
+      await until(() => expect(handleDeviceMessage).toBeCalled());
+
+      // Send the second message which should be received by the debugger
+      device.sendWrappedEvent(page.id, {id: 1337});
+
+      // Ensure only the last message was received by the debugger
+      await until(() => expect(debugger_.handle).toBeCalledWith({id: 1337}));
+      // Ensure the first message was not received by the debugger
+      expect(debugger_.handle).not.toBeCalledWith({id: -1});
+    } finally {
+      device?.close();
+      debugger_?.close();
+      await closeServer(server);
+    }
+  });
+
+  test('debugger message is passed to message middleware', async () => {
+    const handleDebuggerMessage = jest.fn();
+    const {server} = await createServer({
+      logger: undefined,
+      projectRoot: '',
+      unstable_customInspectorMessageHandler: () => ({
+        handleDeviceMessage() {},
+        handleDebuggerMessage,
+      }),
+    });
+
+    let device, debugger_;
+    try {
+      ({device, debugger_} = await createAndConnectTarget(
+        serverRefUrls(server),
+        autoCleanup.signal,
+        page,
+      ));
+
+      // Send a message from the debugger
+      const message = {
+        method: 'Runtime.enable',
+        id: 1337,
+      };
+      debugger_.send(message);
+
+      // Ensure the device received the message
+      await until(() => expect(device.wrappedEvent).toBeCalled());
+      // Ensure the middleware received the message
+      await until(() => expect(handleDebuggerMessage).toBeCalledWith(message));
+    } finally {
+      device?.close();
+      debugger_?.close();
+      await closeServer(server);
+    }
+  });
+
+  test('debugger message stops propagating when handled by middleware', async () => {
+    const handleDebuggerMessage = jest.fn();
+    const {server} = await createServer({
+      logger: undefined,
+      projectRoot: '',
+      unstable_customInspectorMessageHandler: () => ({
+        handleDeviceMessage() {},
+        handleDebuggerMessage,
+      }),
+    });
+
+    let device, debugger_;
+    try {
+      ({device, debugger_} = await createAndConnectTarget(
+        serverRefUrls(server),
+        autoCleanup.signal,
+        page,
+      ));
+
+      // Stop the first message from propagating by returning true (once) from middleware
+      handleDebuggerMessage.mockReturnValueOnce(true);
+
+      // Send the first emssage which should not be received by the device
+      debugger_.send({id: -1});
+      // Send the second message which should be received by the device
+      debugger_.send({id: 1337});
+
+      // Ensure only the last message was received by the device
+      await until(() =>
+        expect(device.wrappedEvent).toBeCalledWith({
+          event: 'wrappedEvent',
+          payload: {pageId: page.id, wrappedEvent: JSON.stringify({id: 1337})},
+        }),
+      );
+      // Ensure the first message was not received by the device
+      expect(device.wrappedEvent).not.toBeCalledWith({id: -1});
+    } finally {
+      device?.close();
+      debugger_?.close();
+      await closeServer(server);
+    }
+  });
+});
+
+function serverRefUrls(server: http$Server | https$Server) {
+  return {
+    serverBaseUrl: baseUrlForServer(server, 'http'),
+    serverBaseWsUrl: baseUrlForServer(server, 'ws'),
+  };
+}
+
+async function closeServer(server: http$Server | https$Server): Promise<void> {
+  return new Promise(resolve => server.close(() => resolve()));
+}