Moti Zilberman
d10a8098b2
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/39107 Augments D48466760 to report debugger commands (request/response pairs) through `EventReporter`. With the appropriate backend integration, this can help validate the correctness/completeness of the CDP implementation (in the client, proxy and server) and measure the latency of debugger commands - more accurately, the time between the proxy receiving a command from the client and receiving the corresponding response from the server. Most of the new logic here is in the `DeviceEventReporter` class, which is responsible for associating responses with requests. Requests are kept in a buffer with a 10s TTL which serves as a timeout in case of an unresponsive server. Changelog: [Internal] Reviewed By: huntie Differential Revision: D48480372 fbshipit-source-id: 55360a14bbea05ef8ad1622e0d54f18b47483809
@react-native/dev-middleware
Dev server middleware supporting core React Native development features. This package is preconfigured in all React Native projects.
Usage
Middleware can be attached to a dev server (e.g. Metro) using the createDevMiddleware API.
import { createDevMiddleware } from '@react-native/dev-middleware';
function myDevServerImpl(args) {
...
const {middleware, websocketEndpoints} = createDevMiddleware({
host: args.host,
port: metroConfig.server.port,
projectRoot: metroConfig.projectRoot,
logger,
});
await Metro.runServer(metroConfig, {
host: args.host,
...,
unstable_extraMiddleware: [
middleware,
// Optionally extend with additional HTTP middleware
],
websocketEndpoints: {
...websocketEndpoints,
// Optionally extend with additional WebSocket endpoints
},
});
}
Included middleware
@react-native/dev-middleware is designed for integrators such as @expo/dev-server and @react-native/community-cli-plugin. It provides a common default implementation for core React Native dev server responsibilities.
We intend to keep this to a narrow set of functionality, based around:
- Debugging — The Chrome DevTools protocol (CDP) endpoints supported by React Native, including the Inspector Proxy, which facilitates connections with multiple devices.
- Dev actions — Endpoints implementing core Dev Menu actions, e.g. reloading the app, opening the debugger frontend.
HTTP endpoints
DevMiddlewareAPI.middleware
These are exposed as a connect middleware handler, assignable to Metro.runServer or other compatible HTTP servers.
GET /json/list, /json (CDP)
Returns the list of available WebSocket targets for all connected React Native app sessions.
GET /json/version (CDP)
Returns version metadata used by Chrome DevTools.
POST /open-debugger
Open the JavaScript debugger for a given CDP target (direct Hermes debugging).
Example
curl -X POST 'http://localhost:8081/open-debugger?appId=com.meta.RNTester'
WebSocket endpoints
DevMiddlewareAPI.websocketEndpoints
/inspector/device
WebSocket handler for registering device connections.
/inspector/debug
WebSocket handler that proxies CDP messages to/from the corresponding device.