feat!: port build internals from unbuild to tsdown

.github/workflows/ci.yml

@@ -62,3 +62,23 @@ jobs:
 
       - name: 💪 Type check
         run: pnpm test:types
+
+  engines-floor:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+      - uses: pnpm/setup@fa36a5ef7dcdefc3a7cb25655c122e00cf6e636e # v3.1.2
+        with:
+          runtime: node@22.18.0
+          cache: true
+
+      - name: 🔍 Check Node.js version
+        run: pnpm exec node -e "if (process.version !== 'v22.18.0') { console.error('Expected v22.18.0, got ' + process.version); process.exit(1) }"
+
+      - run: pnpm dev:prepare
+
+      - name: 🧪 Test project
+        run: pnpm test
+
+      - name: 🛠 Build project (example)
+        run: pnpm example:build

README.md

@@ -10,13 +10,15 @@
 ## Features
 
 - Compatible with Nuxt 3 and Nuxt Kit
-- Unified build with [unjs/unbuild](https://github.com/unjs/unbuild)
+- Unified build with [tsdown](https://tsdown.dev)
 - Automated build config using last module spec
 - Typescript and ESM support
 - Auto generated types and shims for `@nuxt/schema`
 
 We recommend to checkout the [Nuxt modules author guide](https://nuxt.com/docs/guide/going-further/modules) before starting with the module-builder.
 
+Upgrading a module from v1? Follow the [upgrade guide](./docs/upgrade-v2.md).
+
 ## Requirements
 
 For a user to use a module generated from module-builder, it's recommended they have:
@@ -84,7 +86,7 @@ export default defineNuxtModule<ModuleOptions>({
 
 Any runtime file and code that we need to provide by module including plugins, composables and server api, should be in this directory.
 
-Each file will be transformed individually using [unjs/mkdist](https://github.com/unjs/mkdist) to `dist/runtime/`.
+Each file will be transformed individually to `dist/runtime/`.
 
 <!-- TODO: Docs about how to address runtime from within setup -->
 
@@ -121,37 +123,74 @@ A minimum `package.json` should look like this:
     "@nuxt/kit": "latest"
   },
   "devDependencies": {
-    "@nuxt/module-builder": "latest"
+    "@nuxt/module-builder": "latest",
+    "tsdown": "^0.23.7"
   }
 }
 ```
 
-### `build.config.ts` (optional)
+`tsdown` is a peer dependency, so it has to be installed alongside `@nuxt/module-builder`.
 
-Module builder is essentially a preset for [unjs/unbuild](https://github.com/unjs/unbuild), check out the [build command](./src/commands/build.ts#L51) for reference.
+### Additional entrypoints (optional)
 
-To customize/extend the unbuild configuration you can add a `build.config.ts` in the root of your project:
+Module builder is essentially a preset for [tsdown](https://tsdown.dev); check out the [build command](./src/build/build.ts) for reference.
 
-```ts
-import { defineBuildConfig } from 'unbuild'
+Entrypoints other than `src/module` can be listed under the `build.entries` field of your `package.json`:
 
-export default defineBuildConfig({
-  // set additional configuration or customize using hooks
-})
+```json [package.json]
+{
+  "build": {
+    "entries": [
+      "./src/utils"
+    ]
+  }
+}
 ```
 
+> [!WARNING]
+> `build.config.ts` and the `unbuild` field of `package.json` are deprecated.
+> Their `entries`, `externals`, `replace` and `rollup.replace` options are still applied,
+> and so are the `build:before`, `rollup:done` and `build:done` hooks. `mkdist:*` hooks are
+> ignored. Any other option, including other hooks and the rest of `rollup`, makes the
+> build fail. See the [upgrade guide](./docs/upgrade-v2.md#build-configuration).
+>
+> Import `defineBuildConfig` from `@nuxt/module-builder` rather than `unbuild`. Hooks receive
+> a context with `options.name`, `options.rootDir`, `options.outDir`, `options.entries`,
+> `options.declaration`, `options.stub`, `options.sourcemap` and `pkg`.
+
 ## Dist files
 
 Module builder generates dist files in `dist/` directory:
 
 - `module.mjs`: Module entrypoint build from `src/module`
 - `module.json`: Module meta extracted from `module.mjs` + `package.json`
 - `types.d.mts`: Exported types in addition to shims for `nuxt.config` auto completion.
-- `runtime/*`: Individually transformed files using [unjs/mkdist](https://github.com/unjs/mkdist)
-  - Javascript and `.ts` files will be transformed to `.js` with extracted types on `.d.ts` file with same name
-  - `.vue` files will be transformed with extracted `.d.ts` file
+- `runtime/*`: Individually transformed files
+  - JavaScript and `.ts` files will be transformed to `.js` with extracted types in a `.d.ts` file with the same name
+  - `.vue` files will be transformed with extracted `.d.vue.ts` and `.vue.d.ts` files
+  - `.css` files will be nested-flattened, prefixed and minified
+  - `.scss` and `.sass` files will be compiled to `.css` with the module's `sass` or `sass-embedded`; `_` partials are not emitted
   - Other files will be copied as is
 
+## Transpiling a directory with tsdown
+
+The runtime build is a rolldown plugin, `transpileDir`, exported from `@nuxt/module-builder/rolldown` for any tsdown or rolldown build that needs a directory transpiled file by file rather than bundled:
+
+```ts
+// tsdown.config.ts
+import { defineConfig } from 'tsdown'
+import { transpileDir } from '@nuxt/module-builder/rolldown'
+
+export default defineConfig({
+  entry: ['src/index.ts'],
+  plugins: [
+    transpileDir({ srcDir: 'src/runtime', outBase: 'runtime' }),
+  ],
+})
+```
+
+Every file under `srcDir` is emitted under `outBase` in the build's output directory with its name intact. Scripts are transpiled with oxc and keep their imports as written, apart from relative imports, which get the emitted extension. `.vue` files go through `vue-sfc-transformer`, stylesheets are processed as above, and other files are copied. Declarations come from one TypeScript program using the nearest `tsconfig.json`. The options are documented on `TranspileDirOptions`; `resolveExternal` decides what happens to relative imports that resolve outside `srcDir`. A build with nothing to bundle can pass `emptyEntry` from the same export as its `entry`.
+
 ## 💻 Development
 
 - Clone repository