> For AI agents: the complete documentation index is available at https://rspack.rs/llms.txt, the full documentation bundle is available at https://rspack.rs/llms-full.txt. # NestJS Rspack can build [NestJS](https://nestjs.com/) applications. Compared with `tsc`, Rspack can bundle application code, transform TypeScript with SWC, enable development HMR, and leave runtime dependencies external when needed. ## How to use Start with the common [Node.js application configuration](https://rspack.rs/guide/integrations/node.md), then add the NestJS settings described below. You can also use the [NestJS example](https://github.com/rstackjs/rstack-examples/tree/main/rspack/nestjs) in `rstack-examples` as a reference. It includes a complete `rspack.config.mjs`, development script, production build script, and HMR entry. ## Example The [rstack-examples](https://github.com/rstackjs/rstack-examples/tree/main/rspack/nestjs) repository contains a complete NestJS application built with Rspack. ## Install dependencies Install the common Node.js build dependencies from the [Node.js guide](https://rspack.rs/guide/integrations/node.md#install-dependencies), then install the NestJS runtime packages: ```sh [npm] npm add @nestjs/common @nestjs/core @nestjs/platform-express reflect-metadata rxjs ``` ```sh [yarn] yarn add @nestjs/common @nestjs/core @nestjs/platform-express reflect-metadata rxjs ``` ```sh [pnpm] pnpm add @nestjs/common @nestjs/core @nestjs/platform-express reflect-metadata rxjs ``` ```sh [bun] bun add @nestjs/common @nestjs/core @nestjs/platform-express reflect-metadata rxjs ``` ```sh [deno] deno add npm:@nestjs/common npm:@nestjs/core npm:@nestjs/platform-express npm:reflect-metadata npm:rxjs ``` ## Basic concepts NestJS applications run in Node.js, so most configurations can follow the common [Node.js configuration](https://rspack.rs/guide/integrations/node.md). The main NestJS-specific requirement is decorator metadata, which NestJS uses at runtime. - **Decorator metadata**: Enable TypeScript decorators and emitted metadata so dependency injection, controllers, routes, guards, interceptors, and other NestJS features work correctly. - **HMR cleanup**: When development HMR updates the server bundle, close the previous Nest application instance before accepting the update. - **Production minification**: Keep class and function names stable because NestJS may use them through metadata reflection and execution context APIs. ## Configure Rspack The following configuration is adapted from the NestJS example. It combines the common Node.js setup with the decorator metadata options required by NestJS: ```js title="rspack.config.mjs" // @ts-check import { defineConfig } from '@rspack/cli'; import { rspack } from '@rspack/core'; import { RunScriptWebpackPlugin } from 'run-script-webpack-plugin'; import nodeExternals from 'webpack-node-externals'; export default defineConfig({ context: import.meta.dirname, target: 'node', entry: { main: process.env.NODE_ENV === 'production' ? './src/main.ts' : ['@rspack/core/hot/poll?100', './src/main.ts'], }, output: { clean: true, }, resolve: { extensions: ['...', '.ts', '.tsx', '.jsx'], }, module: { rules: [ { test: /\.ts$/, use: { loader: 'builtin:swc-loader', options: { detectSyntax: 'auto', jsc: { parser: { decorators: true, }, transform: { legacyDecorator: true, decoratorMetadata: true, }, }, }, }, }, ], }, optimization: { minimizer: [ new rspack.SwcJsMinimizerRspackPlugin({ minimizerOptions: { compress: { keep_classnames: true, keep_fnames: true, }, mangle: { keep_classnames: true, keep_fnames: true, }, }, }), ], }, plugins: [ process.env.NODE_ENV !== 'production' && new RunScriptWebpackPlugin({ name: 'main.js', autoRestart: false, }), ], devServer: { devMiddleware: { writeToDisk: true, }, }, externals: [ nodeExternals({ allowlist: [/@rspack\/core\/hot\/poll/], }), ], }); ``` ## Configure scripts Use `rspack dev` during development and `rspack build` for production: ```json title="package.json" { "scripts": { "build": "rspack build", "dev": "rspack dev", "start": "node dist/main.js" } } ``` - `dev`: Runs Rspack Dev Server, writes the server bundle to disk, and starts `dist/main.js`. - `build`: Creates a production bundle without the HMR polling entry. - `start`: Runs the production bundle with Node.js. ## Configure TypeScript decorators NestJS uses decorators such as `@Module()`, `@Controller()`, `@Injectable()`, and `@Get()`. Configure `builtin:swc-loader` so SWC can parse these decorators and emit the metadata NestJS needs: ```js title="rspack.config.mjs" export default { module: { rules: [ { test: /\.ts$/, use: { loader: 'builtin:swc-loader', options: { detectSyntax: 'auto', jsc: { parser: { decorators: true, }, transform: { legacyDecorator: true, decoratorMetadata: true, }, }, }, }, }, ], }, }; ``` If your project also runs `tsc`, keep `experimentalDecorators` and `emitDecoratorMetadata` enabled in `tsconfig.json` so TypeScript and Rspack use the same decorator assumptions: ```json title="tsconfig.json" { "compilerOptions": { "experimentalDecorators": true, "emitDecoratorMetadata": true } } ``` ## Configure development HMR Add `@rspack/core/hot/poll` only in development. If it is included in the production bundle, the Node.js application will fail at runtime because HMR is not available in build mode: ```js title="rspack.config.mjs" export default { entry: { main: process.env.NODE_ENV === 'production' ? './src/main.ts' : ['@rspack/core/hot/poll?100', './src/main.ts'], }, }; ``` Add HMR handling to the NestJS bootstrap file. This closes the old application instance before accepting the updated module: ```ts title="src/main.ts" declare const module: any; import { NestFactory } from '@nestjs/core'; import { AppModule } from './app.module'; async function bootstrap() { const app = await NestFactory.create(AppModule); await app.listen(3000); if (module.hot) { module.hot.accept(); module.hot.dispose(() => app.close()); } } bootstrap(); ``` See [Node.js - Configure development HMR](https://rspack.rs/guide/integrations/node.md#configure-development-hmr) for the shared Rspack entry, `writeToDisk`, `RunScriptWebpackPlugin`, and externals allowlist settings used with this bootstrap code. If your project needs ESM output, see [Node.js - Use ESM output](https://rspack.rs/guide/integrations/node.md#use-esm-output). ## Configure production minification When minifying a NestJS server bundle, keep class names and function names. NestJS can rely on stable class and handler references through metadata reflection and execution context APIs. ```js title="rspack.config.mjs" import { rspack } from '@rspack/core'; export default { optimization: { minimizer: [ new rspack.SwcJsMinimizerRspackPlugin({ minimizerOptions: { compress: { keep_classnames: true, keep_fnames: true, }, mangle: { keep_classnames: true, keep_fnames: true, }, }, }), ], }, }; ``` ## Native node modules If a NestJS dependency includes a Node.js native addon (`.node` module), follow [Node.js - Native node modules](https://rspack.rs/guide/integrations/node.md#native-node-modules) to emit the addon with `asset/resource` and let Node.js load it at runtime.