--- name: docs-rsc-sandpack description: Use when adding interactive RSC (React Server Components) code examples to React docs using , or when modifying the RSC sandpack infrastructure. --- # RSC Sandpack Patterns For general Sandpack conventions (code style, naming, file naming, line highlighting, hidden files, CSS guidelines), see `/docs-sandpack`. This skill covers only RSC-specific patterns. ## Quick Start Template Minimal single-file `` example: ```mdx ` ` `js src/App.js export default function App() { return

Hello from a Server Component!

; } ` ` ` ``` --- ## How It Differs from `` | Feature | `` | `` | |---------|-------------|-----------------| | Execution model | All code runs in iframe | Server code runs in Web Worker, client code in iframe | | `'use client'` directive | Ignored (everything is client) | Required to mark client components | | `'use server'` directive | Not supported | Marks Server Functions callable from client | | `async` components | Not supported | Supported (server components can be async) | | External dependencies | Supported via `package.json` | Not supported (only React + react-dom) | | Entry point | `App.js` with `export default` | `src/App.js` with `export default` | | Component tag | `` | `` | --- ## File Directives Files are classified by the directive at the top of the file: | Directive | Where it runs | Rules | |-----------|--------------|-------| | (none) | Web Worker (server) | Default. Can be `async`. Can import other server files. Cannot use hooks, event handlers, or browser APIs. | | `'use client'` | Sandpack iframe (browser) | Must be first statement. Can use hooks, event handlers, browser APIs. Cannot be `async`. Cannot import server files. | | `'use server'` | Web Worker (server) | Marks Server Functions. Can be module-level (all exports are actions) or function-level. Callable from client via props or form `action`. | --- ## Common Patterns ### 1. Server + Client Components ```mdx ` ` `js src/App.js import Counter from './Counter'; export default function App() { return (

Server-rendered heading

); } ` ` ` ` ` `js src/Counter.js 'use client'; import { useState } from 'react'; export default function Counter() { const [count, setCount] = useState(0); return ( ); } ` ` ` ``` ### 2. Async Server Component with Suspense ```mdx ` ` `js src/App.js import { Suspense } from 'react'; import Albums from './Albums'; export default function App() { return ( Loading...

}> ); } ` ` ` ` ` `js src/Albums.js async function fetchAlbums() { await new Promise(resolve => setTimeout(resolve, 1000)); return ['Abbey Road', 'Let It Be', 'Revolver']; } export default async function Albums() { const albums = await fetchAlbums(); return (

{album}

); } ` ` ` ``` ### 3. Server Functions (Actions) ```mdx ` ` `js src/App.js import { addLike, getLikeCount } from './actions'; import LikeButton from './LikeButton'; export default async function App() { const count = await getLikeCount(); return (

Likes: {count}

); } ` ` ` ` ` `js src/actions.js 'use server'; let count = 0; export async function addLike() { count++; } export async function getLikeCount() { return count; } ` ` ` ` ` `js src/LikeButton.js 'use client'; export default function LikeButton({ addLike }) { return ( ); } ` ` ` ``` --- ## File Structure Requirements ### Entry Point - **`src/App.js` is required** as the main entry point - Must have `export default` (function component) - Case-insensitive fallback: `src/app.js` also works ### Auto-Injected Infrastructure Files These files are automatically injected by `sandpack-rsc-setup.ts` and should never be included in MDX: | File | Purpose | |------|---------| | `/src/index.js` | Bootstraps the RSC pipeline | | `/src/rsc-client.js` | Client bridge — creates Worker, consumes Flight stream | | `/src/rsc-server.js` | Wraps pre-bundled worker runtime as ES module | | `/node_modules/__webpack_shim__/index.js` | Minimal webpack compatibility layer | | `/node_modules/__rsdw_client__/index.js` | `react-server-dom-webpack/client` as local dependency | ### No External Dependencies `` does not support external npm packages. Only `react` and `react-dom` are available. Do not include `package.json` in RSC examples. --- ## Architecture Reference ### Three-Layer Architecture ``` react.dev page (Next.js) ┌─────────────────────────────────────────┐ │ │ │ ┌─────────┐ ┌──────────────────────┐ │ │ │ Editor │ │ Preview (iframe) │ │ │ │ App.js │ │ Client React app │ │ │ │ (edit) │ │ consumes Flight │ │ │ │ │ │ stream from Worker │ │ │ └─────────┘ └──────────┬───────────┘ │ └───────────────────────────┼─────────────┘ │ postMessage ┌───────────────────────────▼─────────────┐ │ Web Worker (Blob URL) │ │ - React server build (pre-bundled) │ │ - react-server-dom-webpack/server │ │ - webpack shim │ │ - User server code (Sucrase → CJS) │ └─────────────────────────────────────────┘ ``` ### Key Source Files | File | Purpose | |-----------------------------------------------------------------|--------------------------------------------------------------------------------| | `src/components/MDX/Sandpack/sandpack-rsc/RscFileBridge.tsx` | Monitors Sandpack; posts raw files to iframe | | `src/components/MDX/Sandpack/SandpackRSCRoot.tsx` | SandpackProvider setup, custom bundler URL, UI layout | | `src/components/MDX/Sandpack/templateRSC.ts` | RSC template files | | `.../sandbox-code/src/__react_refresh_init__.js` | React Refresh shim | | `.../sandbox-code/src/rsc-server.js` | Worker runtime: module system, Sucrase compilation, `renderToReadableStream()` | | `.../sandbox-code/src/rsc-client.source.js` | Client bridge: Worker creation, file classification, Flight stream consumption | | `.../sandbox-code/src/webpack-shim.js` | Minimal `__webpack_require__` / `__webpack_module_cache__` shim | | `.../sandbox-code/src/worker-bundle.dist.js` | Pre-bundled IIFE (generated): React server + RSDW/server + Sucrase | | `scripts/buildRscWorker.mjs` | esbuild script: bundles rsc-server.js into worker-bundle.dist.js | --- ## Build System ### Rebuilding the Worker Bundle After modifying `rsc-server.js` or `webpack-shim.js`: ```bash node scripts/buildRscWorker.mjs ``` This runs esbuild with: - `format: 'iife'`, `platform: 'browser'` - `conditions: ['react-server', 'browser']` (activates React server export conditions) - `minify: true` - Prepends `webpack-shim.js` to the output ### Raw-Loader Configuration In `templateRSC.js` files are loaded as raw strings with the `!raw-loader`. The strings are necessary to provide to Sandpack as local files (skips Sandpack bundling). ### Development Commands ```bash node scripts/buildRscWorker.mjs # Rebuild worker bundle after source changes yarn dev # Start dev server to test examples ```

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