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.cursor/skills/antfu/references/library-development.md

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+---
+name: library-development
+description: Anthony Fu's preferences for building and publishing JavaScript/TypeScript libraries
+---
+
+# Library Development Preferences
+
+Preferences for bundling and publishing TypeScript libraries.
+
+## Key Decisions
+
+| Aspect | Choice |
+|--------|--------|
+| Bundler | tsdown |
+| Output | Pure ESM only (no CJS) |
+| DTS | Generated via tsdown |
+| Exports | Auto-generated via tsdown |
+
+---
+
+## tsdown Configuration
+
+Use tsdown with these options enabled:
+
+```ts
+// tsdown.config.ts
+import { defineConfig } from 'tsdown'
+
+export default defineConfig({
+  entry: ['src/index.ts'],
+  format: ['esm'],
+  dts: true,
+  exports: true,
+})
+```
+
+| Option | Value | Purpose |
+|--------|-------|---------|
+| `format` | `['esm']` | Pure ESM, no CommonJS |
+| `dts` | `true` | Generate `.d.ts` files |
+| `exports` | `true` | Auto-update `exports` field in `package.json` |
+
+### Multiple Entry Points
+
+```ts
+export default defineConfig({
+  entry: [
+    'src/index.ts',
+    'src/utils.ts',
+  ],
+  format: ['esm'],
+  dts: true,
+  exports: true,
+})
+```
+
+The `exports: true` option auto-generates the `exports` field in `package.json` when running `tsdown`.
+
+---
+
+## package.json
+
+Required fields for pure ESM library:
+
+```json
+{
+  "type": "module",
+  "main": "./dist/index.mjs",
+  "module": "./dist/index.mjs",
+  "types": "./dist/index.d.mts",
+  "files": ["dist"],
+  "scripts": {
+    "build": "tsdown",
+    "prepack": "pnpm build",
+    "test": "vitest",
+    "release": "bumpp -r"
+  }
+}
+```
+
+The `exports` field is managed by tsdown when `exports: true`.
+
+### prepack Script
+
+For each public package, add `"prepack": "pnpm build"` to `scripts`. This ensures the package is automatically built before publishing (e.g., when running `npm publish` or `pnpm publish`). This prevents accidentally publishing stale or missing build artifacts.