{
    "compilerOptions": {
      "target": "ESNext",
      "jsx": "preserve",
      "lib": ["DOM", "ESNext"],
      "baseUrl": ".",
      "module": "ESNext",
      "moduleResolution": "node",
      "paths": {
        "@/*": ["./src/*"]
      },
      "resolveJsonModule": true,
      "types": ["node"],
      "strict": true,
      "strictNullChecks": true,
      "noUnusedLocals": true,
      "allowSyntheticDefaultImports": true,
      "esModuleInterop": true,
      "forceConsistentCasingInFileNames": true
    },
    "exclude": ["node_modules", "dist"]
  }

// package.json

{
  "type": "module",
  "exports": {
    ".": {
      "import": "./dist/index.mjs",
      "require": "./dist/index.cjs"
    }
  },
  "main": "./dist/index.cjs",
  "types": "./dist/index.d.ts",
  "files": ["dist"]
}

import { defineBuildConfig } from 'unbuild'

export default defineBuildConfig({
  entries: ['src/index'],
  clean: true,
  declaration: true,
  rollup: {
    emitCJS: true,
    inlineDependencies: true,
    esbuild: {
      minify: true,
    },
  },
})

λ yarn build

yarn run v1.22.4
$ unbuild
ℹ Building my-package                                                                                                                                                                                       14:27:10
ℹ Cleaning dist directory: ./dist                                                                                                                                                                           14:27:10
✔ Build succeeded for my-package                                                                                                                                                                            14:27:10
  dist/index.cjs (total size: 59 B, chunk size: 59 B, exports: add)                                                                                                                                          14:27:10

  dist/index.mjs (total size: 45 B, chunk size: 45 B, exports: add)                                                                                                                                          14:27:10

Σ Total dist size (byte size): 329 B
                                                                                                                                                                                                             14:27:10
✨  Done in 1.00s.

// build.config.ts
import { defineBuildConfig } from 'unbuild'
import { join } from "node:path"

export default defineBuildConfig({
    entries: ['src/index'],
    clean: true,
    declaration: true,
    rollup: {
        emitCJS: true,
        inlineDependencies: true,
        esbuild: {
            minify: true,
        },
    },
    alias: {
        '@': join(__dirname, 'src')
    },
})

{
    "compilerOptions": {
        "target": "ESNext",
        "jsx": "preserve",
        "lib": [
            "DOM",
            "ESNext"
        ],
        "baseUrl": ".",
        "module": "ESNext",
        "moduleResolution": "node",
        "paths": {
            "@/*": [
                "./src/*"
            ]
        },
        "resolveJsonModule": true,
        "types": [
            "node"
        ],
        "strict": true,
        "strictNullChecks": true,
        "noUnusedLocals": true,
        "allowSyntheticDefaultImports": true,
        "esModuleInterop": true,
        "forceConsistentCasingInFileNames": true
    },
    "exclude": [
        "node_modules",
        "dist"
    ]
}

/**
 * * `compatible` means "src/index.ts" will generate "dist/index.d.mts", "dist/index.d.cts" and "dist/index.d.ts".
 * * `node16` means "src/index.ts" will generate "dist/index.d.mts" and "dist/index.d.cts".
 * * `true` is equivalent to `compatible`.
 * * `false` will disable declaration generation.
 * * `undefined` will auto detect based on "package.json". If "package.json" has "types" field, it will be `"compatible"`, otherwise `false`.
 */
declaration?: "compatible" | "node16" | boolean;

λ  npx unbuild --stub

ℹ Stubbing my-package                                                                                                                                                                                       14:38:07
ℹ Cleaning dist directory: ./dist