Moti Zilberman
55ff50fba5
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/51687 Changelog: [Internal] # Context This is the first of several commits that aim to implement a **standalone shell for React Native DevTools**. This will be a lightweight desktop app designed to host the debugger frontend, in much the same way as we currently use Chrome or Edge. The launch flow will otherwise remain **very similar** to the one that exists today. ## What's changing for users? 1. With this commit, nothing; we're merely setting up an experiment flag (for stage 1 - Meta-internal testing) and will make separate plans for open source rollout, coordinated with our framework maintainer partners. 2. If the experiment is successful, we aim to *eventually* phase out the use of Chrome/Edge in React Native DevTools and ship the standalone shell as standard to all React Native developers. This is to enable further improvements that will rely on the standalone shell to work. 3. The first iteration of the standalone shell aims to solve some concrete pain points such as the "dead window problem" - the fact that opening DevTools multiple times for the same target will leave behind a now-dead window (that would ideally have been reused). ## This diff We amend the `unstable_experiments` and `unstable_browserLauncher` APIs in `dev-middleware` to add basic support for launching a standalone shell based on a frontend URL and a *window key* - the latter being an opaque string that the shell process can match against previous launches in order to reuse and foreground existing windows. We leave it up to `BrowserLauncher` implementers ( = frameworks) to provide a working implementation of `unstable_showFuseboxShell`, and do not provide one with `DefaultBrowserLauncher`. This will effectively allow us to dependency-inject the actual shell implementation at stage 1 so we don't increase the download size of React Native unnecessarily. Reviewed By: rickhanlonii, robhogan Differential Revision: D74904547 fbshipit-source-id: fbc6eac97923062bda8892bc130b39051845ea82
@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. Must be provided with one of the following query params:
device — An ID unique to a combination of device and app, stable across installs. Implemented bygetInspectorDeviceIdon each native platform.target— The target page ID as returned by/json/listfor the current dev server session.appId(deprecated, legacy only) — The application bundle identifier to match (non-unique across multiple connected devices). This param will only match legacy Hermes debugger targets.
Example
curl -X POST 'http://localhost:8081/open-debugger?target=<targetId>'
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.