Rob Hogan
ac714b1c33
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/43639 Currently, the `react-native/dev-middleware` inspector proxy intercepts `Debugger.scriptParsed` notifications from the target and replaces `sourceMapURL` with a data uri, via an async fetch from Metro. During this async fetch, other notifications from the debugger may pass through the proxy, which results in the frontend receiving them before `Debugger.scriptParsed`. This reordering causes problems in breakpoint resolution and pausing, because `Debugger.breakpointResolved` and `Debugger.paused` events may reference `scriptId`s unknown to the frontend while the corresponding `Debugger.scriptParsed` is delayed. In particular, breakpoint UI state and backend state can fall out of sync, and breakpoints hit may open to the incorrect source location. This diff modifies the proxy to use a simple per-target promise queue to ensure messages are handled in the order they were received from the target. Changelog: [General][Fixed] Fix breakpoints opening to incorrect location or disappearing from debugger frontend UI. Reviewed By: motiz88 Differential Revision: D55200617 fbshipit-source-id: 27c95f822266875ed668d0bf8a525da49554cafd
@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({
projectRoot: metroConfig.projectRoot,
serverBaseUrl: `http://${args.host}:${args.port}`,
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.
GET /debugger-frontend
Subpaths of this endpoint are reserved to serve the JavaScript debugger frontend.
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.
Contributing
Changes to this package can be made locally and tested against the rn-tester app, per the Contributing guide. During development, this package is automatically run from source with no build step.