Update DevTools READMEs (#24105)

Author: Brian Vaughn

packages/react-devtools-core/README.md

@@ -1,66 +1,122 @@
 # `react-devtools-core`
 
-A standalone React DevTools implementation.
+This package provides low-level APIs to support renderers like [React Native](https://github.com/facebook/react-native). If you're looking for the standalone React DevTools UI, **we suggest using [`react-devtools`](https://github.com/facebook/react/tree/main/packages/react-devtools) instead of using this package directly**.
 
-This is a low-level package. If you're looking for the Electron app you can run, **use `react-devtools` package instead.**
+This package provides two entrypoints: labeled "backend" and "standalone" (frontend). Both APIs are described below.
 
-## API
+# Backend API
 
-### `react-devtools-core`
+Backend APIs are embedded in _development_ builds of renderers like [React Native](https://github.com/facebook/react-native) in order to connect to the React DevTools UI.
 
-This is similar requiring the `react-devtools` package, but provides several configurable options. Unlike `react-devtools`, requiring `react-devtools-core` doesn't connect immediately but instead exports a function:
+### Example
+
+If you are building a non-browser-based React renderer, you can use the backend API like so:
 
 ```js
-const { connectToDevTools } = require("react-devtools-core");
-connectToDevTools(config);
+if (process.env.NODE_ENV !== 'production') {
+  const { connectToDevTools } = require("react-devtools-core");
+
+  // Must be called before packages like react or react-native are imported
+  connectToDevTools({
+    ...config
+  });
+}
 ```
 
-Run `connectToDevTools()` in the same context as React to set up a connection to DevTools.  
-Be sure to run this function *before* importing e.g. `react`, `react-dom`, `react-native`.
+> **NOTE** that this API (`connectToDevTools`) must be (1) run in the same context as React and (2) must be called before React packages are imported (e.g. `react`, `react-dom`, `react-native`).
+
+### `connectToDevTools` options
+| Prop | Default | Description |
+|---|---|---|
+| `host` | `"localhost"` | Socket connection to frontend should use this host. |
+| `isAppActive` |  | (Optional) function that returns true/false, telling DevTools when it's ready to connect to React. |
+| `port` | `8097` | Socket connection to frontend should use this port. |
+| `resolveRNStyle` |  | (Optional) function that accepts a key (number) and returns a style (object); used by React Native. |
+| `retryConnectionDelay` | `200` | Delay (ms) to wait between retrying a failed Websocket connection |
+| `useHttps` | `false` | Socket connection to frontend should use secure protocol (wss). |
+| `websocket` |  | Custom `WebSocket` connection to frontend; overrides `host` and `port` settings. |
+
+# Frontend API
+
+Frontend APIs can be used to render the DevTools UI into a DOM node. One example of this is [`react-devtools`](https://github.com/facebook/react/tree/main/packages/react-devtools) which wraps DevTools in an Electron app.
+
+### Example
+```js
+import DevtoolsUI from "react-devtools-core/standalone";
+
+// See the full list of API methods in documentation below.
+const { setContentDOMNode, startServer } = DevtoolsUI;
+
+// Render DevTools UI into a DOM element.
+setContentDOMNode(document.getElementById("container"));
+
+// Start socket server used to communicate between backend and frontend.
+startServer(
+  // Port defaults to 8097
+  1234,
 
-The `config` object may contain:
-* `host: string` (defaults to "localhost") - Websocket will connect to this host.
-* `port: number` (defaults to `8097`) - Websocket will connect to this port.
-* `useHttps: boolean` (defaults to `false`) - Websocket should use a secure protocol (wss).
-* `websocket: Websocket` - Custom websocket to use. Overrides `host` and `port` settings if provided.
-* `resolveRNStyle: (style: number) => ?Object` - Used by the React Native style plug-in.
-* `retryConnectionDelay: number` (defaults to `2000`) - Milliseconds delay to wait between retrying a failed Websocket connection.
-* `isAppActive: () => boolean` - If provided, DevTools will poll this method and wait until it returns true before connecting to React.
+  // Host defaults to "localhost"
+  "example.devserver.com",
 
-## `react-devtools-core/standalone`
+  // Optional config for secure socket (WSS).
+  {
+    key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),
+    cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')
+  }
+);
+```
 
-Renders the DevTools interface into a DOM node.
+### Exported methods
+The `default` export is an object defining the methods described below.
 
+These methods support chaining for convenience. For example:
 ```js
-require("react-devtools-core/standalone")
-  .setContentDOMNode(document.getElementById("container"))
-  .setStatusListener(status => {
-    // This callback is optional...
-  })
-  .startServer(port);
+const DevtoolsUI = require("react-devtools-core/standalone");
+DevtoolsUI.setContentDOMNode(element).startServer();
 ```
 
-Renders DevTools interface into a DOM node over SSL using a custom host name (Default is localhost).
+#### `connectToSocket(socket: WebSocket)`
+> This is an advanced config function that is typically not used.
+
+Custom `WebSocket` connection to use for communication between DevTools frontend and backend. Calling this method automatically initializes the DevTools UI (similar to calling `startServer()`).
+
+#### `openProfiler()`
+Automatically select the "Profiler" tab in the DevTools UI.
+
+#### `setContentDOMNode(element: HTMLElement)`
+Set the DOM element DevTools UI should be rendered into on initialization.
+
+#### `setDisconnectedCallback(callback: Function)`
+_Optional_ callback to be notified when DevTools `WebSocket` closes (or errors).
 
+#### `setProjectRoots(roots: Array<string>)`
+_Optional_ set of root directores for source files. These roots can be used to open an inspected component's source code using an IDE.
+
+#### `setStatusListener(callback: Function)`
+_Optional_ callback to be notified of socket server events (e.g. initialized, errored, connected).
+
+This callback receives two parameters:
 ```js
-const host = 'dev.server.com';
-const options = {
-  key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),
-  cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')
-};
-
-
-require("react-devtools-core/standalone")
-  .setContentDOMNode(document.getElementById("container"))
-  .setStatusListener(status => {
-    // This callback is optional...
-  })
-  .startServer(port, host, options);
+function onStatus(
+  message: string,
+  status: 'server-connected' | 'devtools-connected' | 'error'
+): void {
+  // ...
+}
 ```
 
-Reference the `react-devtools` package for a complete integration example.
+#### `startServer(port?: number, host?: string, httpsOptions?: Object, loggerOptions?: Object)`
+Start a socket server (used to communicate between backend and frontend) and renders the DevTools UI.
 
-## Development
+This method accepts the following parameters:
+| Name | Default | Description |
+|---|---|---|
+| `port` | `8097` | Socket connection to backend should use this port. |
+| `host` | `"localhost"` | Socket connection to backend should use this host. |
+| `httpsOptions` | | _Optional_ object defining `key` and `cert` strings. |
+| `loggerOptions` | | _Optional_ object defining a `surface` string (to be included with DevTools logging events). |
+
+# Development
 
 Watch for changes made to the backend entry point and rebuild:
 ```sh
@@ -71,3 +127,5 @@ Watch for changes made to the standalone UI entry point and rebuild:
 ```sh
 yarn start:standalone
 ```
+
+Run the standalone UI using `yarn start` in the [`react-devtools`](https://github.com/facebook/react/tree/main/packages/react-devtools).

packages/react-devtools-inline/README.md

@@ -1,10 +1,16 @@
 # `react-devtools-inline`
 
-React DevTools implementation for embedding within a browser-based IDE (e.g. [CodeSandbox](https://codesandbox.io/), [StackBlitz](https://stackblitz.com/)).
+This package can be used to embed React DevTools into browser-based tools like [CodeSandbox](https://codesandbox.io/), [StackBlitz](https://stackblitz.com/), and [Replay](https://replay.io).
 
-This is a low-level package. If you're looking for the standalone DevTools app, **use the `react-devtools` package instead.**
+If you're looking for the standalone React DevTools UI, **we suggest using [`react-devtools`](https://github.com/facebook/react/tree/main/packages/react-devtools) instead of using this package directly**.
 
-## Usage
+---
+
+> **Note** that this package (and the DevTools UI) relies on several _experimental_ APIs that are **only available in the [experimental release channel](https://reactjs.org/docs/release-channels.html#experimental-channel)**. This means that you will need to install `react@experimental` and `react-dom@experimenal`.
+
+---
+
+# Usage
 
 This package exports two entry points: a frontend (to be run in the main `window`) and a backend (to be installed and run within an `iframe`<sup>1</sup>).
 
@@ -16,15 +22,18 @@ The frontend and backend can be initialized in any order, but **the backend must
 
 <sup>1</sup> Sandboxed iframes are supported.
 
-## API
+# Backend APIs
+### `initialize(windowOrGlobal)`
+
+Installs the global hook on the window/global object. This hook is how React and DevTools communicate.
 
-### `react-devtools-inline/backend`
+> **This method must be called before React is loaded.** (This includes `import`/`require` statements and `<script>` tags that include React.)
+
+### `activate(windowOrGlobal)`
 
-* **`initialize(contentWindow)`** -
-Installs the global hook on the window. This hook is how React and DevTools communicate. **This method must be called before React is loaded.**<sup>2</sup>
-* **`activate(contentWindow)`** -
 Lets the backend know when the frontend is ready. It should not be called until after the frontend has been initialized, else the frontend might miss important tree-initialization events.
 
+### Example
 ```js
 import { activate, initialize } from 'react-devtools-inline/backend';
 
@@ -41,13 +50,14 @@ initialize(contentWindow);
 activate(contentWindow);
 ```
 
-<sup>2</sup> The backend must be initialized before React is loaded. (This means before any `import` or `require` statements or `<script>` tags that include React.)
+# Frontend APIs
 
-### `react-devtools-inline/frontend`
+### `initialize(windowOrGlobal)`
+Configures the DevTools interface to listen to the `window` (or `global` object) the backend was injected into. This method returns a React component that can be rendered directly.
 
-* **`initialize(contentWindow)`** -
-Configures the DevTools interface to listen to the `window` the backend was injected into. This method returns a React component that can be rendered directly<sup>3</sup>.
+> Because the DevTools interface makes use of several new React concurrent features (like Suspense) **it should be rendered using `ReactDOMClient.createRoot` instead of `ReactDOM.render`.**
 
+### Example
 ```js
 import { initialize } from 'react-devtools-inline/frontend';
 
@@ -60,9 +70,7 @@ const contentWindow = iframe.contentWindow;
 const DevTools = initialize(contentWindow);
 ```
 
-<sup>3</sup> Because the DevTools interface makes use of several new React APIs (e.g. suspense, concurrent mode) it should be rendered using `ReactDOMClient.createRoot`. **It should not be rendered with `ReactDOM.render`.**
-
-## Examples
+# Advanced examples
 
 ### Supporting named hooks
 
@@ -169,7 +177,7 @@ iframe.onload = () => {
 };
 ```
 
-### Advanced integration with custom "wall"
+### Advanced: Custom "wall"
 
 Below is an example of an advanced integration with a website like [Replay.io](https://replay.io/) or Code Sandbox's Sandpack (where more than one DevTools instance may be rendered per page).
 
@@ -235,25 +243,116 @@ const wall = {
 };
 ```
 
-## Local development
+### Advanced: Node + browser
+
+Below is an example of an advanced integration that could be used to connect React running in a Node process to React DevTools running in a browser.
+
+##### Sample Node backend
+```js
+const {
+  activate,
+  createBridge,
+  initialize,
+} = require('react-devtools-inline/backend');
+const { createServer } = require('http');
+const SocketIO = require('socket.io');
+
+const server = createServer();
+const socket = SocketIO(server, {
+  cors: {
+    origin: "*",
+    methods: ["GET", "POST"],
+    allowedHeaders: [],
+    credentials: true
+  }
+});
+socket.on('connection', client => {
+  const wall = {
+    listen(listener) {
+      client.on('message', data => {
+        if (data.uid === UID) {
+          listener(data);
+        }
+      });
+    },
+    send(event, payload) {
+      const data = {event, payload, uid: UID};
+      client.emit('message', data);
+    },
+  };
+
+  const bridge = createBridge(global, wall);
+
+  client.on('disconnect', () => {
+    bridge.shutdown();
+  });
+
+  activate(global, { bridge });
+});
+socket.listen(PORT);
+```
+
+##### Sample Web frontend
+```js
+import { createElement } from 'react';
+import { createRoot } from 'react-dom/client';
+import {
+  createBridge,
+  createStore,
+  initialize as createDevTools,
+} from 'react-devtools-inline/frontend';
+import { io } from "socket.io-client";
+
+let root = null;
+
+const socket = io(`http://${HOST}:${PORT}`);
+socket.on("connect", () => {
+  const wall = {
+    listen(listener) {
+      socket.on("message", (data) => {
+        if (data.uid === UID) {
+          listener(data);
+        }
+      });
+    },
+    send(event, payload) {
+      const data = { event, payload, uid: UID };
+      socket.emit('message', data);
+    },
+  };
+
+  const bridge = createBridge(window, wall);
+  const store = createStore(bridge);
+  const DevTools = createDevTools(window, { bridge, store });
+
+  root = createRoot(document.getElementById('root'));
+  root.render(createElement(DevTools));
+});
+socket.on("disconnect", () => {
+  root.unmount();
+  root = null;
+});
+```
+
+# Local development
 You can also build and test this package from source.
 
-### Prerequisite steps
+## Prerequisite steps
 DevTools depends on local versions of several NPM packages<sup>1</sup> also in this workspace. You'll need to either build or download those packages first.
 
 <sup>1</sup> Note that at this time, an _experimental_ build is required because DevTools depends on the `createRoot` API.
 
-#### Build from source
+### Build from source
 To build dependencies from source, run the following command from the root of the repository:
 ```sh
 yarn build-for-devtools
 ```
-#### Download from CI
+### Download from CI
 To use the latest build from CI, run the following command from the root of the repository:
 ```sh
 ./scripts/release/download-experimental-build.js
 ```
-### Build steps
+## Build steps
 Once the above packages have been built or downloaded, you can watch for changes made to the source code and automatically rebuild by running:
 ```sh
 yarn start

packages/react-devtools-shared/README.md

@@ -0,0 +1,6 @@
+This directory contains code shared between several DevTools packages:
+* /packages/react-devtools-core
+* /packages/react-devtools-extensions
+* /packages/react-devtools-inline
+
+It is not published or released anywhere directly.