tsconfig

• Type: string
• Optional: Yes ✅

Specifies the path to a TypeScript configuration file. You may provide a relative path (resolved relative to cwd) or an absolute path.

Examples

Use default tsconfig.json

export default {
  tsconfig: './tsconfig.json',
};

Use custom config

export default {
  tsconfig: './tsconfig.build.json',
};

Use absolute path

export default {
  tsconfig: '/absolute/path/to/tsconfig.json',
};

In-depth

When a tsconfig path is specified, Rolldown will:

1. Use compiler options for transpilation:

• target: ECMAScript version to compile to
• jsx: JSX transformation mode
• experimentalDecorators: Enable decorator support
• emitDecoratorMetadata: Emit decorator metadata

2. Use paths for module resolution:

• compilerOptions.paths: Path mapping for module resolution
• compilerOptions.baseUrl: Base directory for path resolution

3. Merge with transform options:

The tsconfig options will be merged with the top-level transform options, with transform options taking precedence.

Example tsconfig.json:

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "ESNext",
    "jsx": "react-jsx",
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"],
      "@components/*": ["src/components/*"]
    }
  }
}

With this configuration:

• TypeScript will be transpiled to ES2020
• JSX will use React's automatic runtime
• Path aliases like @/utils will resolve to src/utils

Priority

Options specified directly in Rolldown configuration take precedence over tsconfig.json settings:

export default {
  tsconfig: './tsconfig.json', // Has jsx: 'react-jsx'
  transform: {
    jsx: {
      mode: 'classic', // This takes precedence
    },
  },
};

Automatic Discovery

Rolldown will NOT automatically look for tsconfig.json if this option is not specified. You must explicitly provide the path.

TIP

For TypeScript projects, it's recommended to specify tsconfig to ensure consistent compilation behavior and enable path mapping.