rollup-builder provides a utility function to simplify the process of building JavaScript libraries using the Rollup bundler. It allows you to generate various formats such as CommonJS (CJS), ES Module (ESM), and Universal Module Definition (UMD), and gives you the option to choose whether to perform code minification.

• Features
• Installation
• Usage
• Configuration Options
• Mixing Default and Named Exports
• Contributions
• License

• Build JavaScript libraries in multiple formats, making them compatible with a variety of environments.
• Minify your library for production use with ease.
• Automatic generation of sourcemaps for debugging.
• Configure the library's format, filename, and more using simple options.
• You can mix default and named exports in ESM modules and the Rollup will generate code in CJS or UMD format that compatible with both CommonJS and ES6.
• Highly customizable using Rollup plugins and custom configurations.

You can install rollup-builder as a development dependency using npm or yarn:

npm install @haixing_hu/rollup-builder --save-dev
# or
yarn add @haixing_hu/rollup-builder --dev

1. Create a Rollup configuration file (usually named rollup.config.mjs) and export a function that defines the library's build options. You can use the provided rollupBuilder function to streamline this process.

   Example rollup.config.mjs:

   import rollupBuilder from '@haixing_hu/rollup-builder';
   
   export default rollupBuilder('MyLibrary', import.meta.url);

2. Customize the rollup.config.mjs file to match your library's specific requirements. You can specify the input file, formats, filename prefix, and other options. Refer to the Configuration Options section for more details.

   Example rollup.config.mjs:

   import rollupBuilder from '@haixing_hu/rollup-builder';
    
   export default rollupBuilder('MyLibrary', import.meta.url, {
     formats: ['cjs', 'esm'],
     minify: true,
     // Customize additional options as needed.
   });

3. Run the Rollup build process using the following command:

   rollup -c rollup.config.mjs

4. The resulting library files will be placed in the dist directory, following the format you specified. For example, if you specified formats: ['cjs', 'esm'], the following files will be generated:

    dist/my-library.cjs.js
    dist/my-library.cjs.min.js
    dist/my-library.esm.mjs
    dist/my-library.esm.min.mjs

5. You should modify your package.json file to specify the entry point of your library. For example, if you specified formats: ['cjs', 'esm'], you should add the following lines to your package.json file:

   {
     "main": "dist/my-library.cjs.min.js",
     "module": "dist/my-library.esm.min.mjs",
     "exports": {
         ".": {
            "require": "./dist/my-library.cjs.min.js",
            "import": "./dist/my-library.esm.min.mjs"
         }
     }
   }

6. You should add the following dev dependencies to your library:

   yarn add --dev @babel/core @babel/plugin-transform-runtime @babel/preset-env \
     @rollup/plugin-alias @rollup/plugin-babel @rollup/plugin-commonjs \
     @rollup/plugin-node-resolve @rollup/plugin-terser rollup rollup-plugin-analyzer

   or

   npm install -D @babel/core @babel/plugin-transform-runtime @babel/preset-env \
     @rollup/plugin-alias @rollup/plugin-babel @rollup/plugin-commonjs \
     @rollup/plugin-node-resolve @rollup/plugin-terser rollup rollup-plugin-analyzer

• libraryName: string: The name of your library (used in the UMD format).
• importMetaUrl: string: The import.meta.url of the caller module.
• options: object: Additional build options, including:

  • debug: boolean: Whether to print debug information. If this field is not specified, the default value is false.

  • formats: [string]: An array of formats to build. It can be an array of the following values:

    • 'cjs': the CommonJS format.
    • 'umd': the UMD format.
    • 'esm': the ES module format.

    If this field is not specified, the default value is ['cjs', 'esm'].

  • exports: string: the export mode to use. It can be one of the following values:

    • 'auto': automatically guesses your intentions based on what the input module exports.
    • 'default': if you are only exporting one thing using export default ...; note that this can cause issues when generating CommonJS output that is meant to be interchangeable with ESM output.
    • 'named': if you are using named exports.
    • 'none': if you are not exporting anything (e.g. you are building an app, not a library)
    • 'mixed': if you are using named exports mixed with a default export. Note that this is not a standard exports mode officially supported by Rollup, instead, it is an additional mode add by this library. Refer to the Mixing Default and Named Exports for more details.

    If this field is not specified, the default value is 'auto'.

  • nodeEnv: string: The NODE_ENV environment variable. If this field is not specified, the default value is process.env.NODE_ENV.

  • minify: boolean: Whether to minify the code. If this field is not specified, the default value will be true for production environment, and false otherwise.

  • sourcemap: boolean: Whether to generate sourcemaps. If this field is not specified, the default value is true.

  • input: string: The input file of the library. If this field is not specified, the default value is src/index.js.

  • outputDir: string: The output directory of the library. If this field is not specified, the default value is dist.

  • filenamePrefix: string: The prefix for the output filename. If this field is not specified, the default value the dash-case of the library name.

  • externals: [string]: the additional external packages, each can be specified with either a string or a regular expression. If this field is not specified, the default value is an empty array.

  • useAliasPlugin: boolean: whether to use the @rollup/plugin-alias plugin. If this field is not specified, the default value is true.

  • aliasPluginOptions: object: the options for the @rollup/plugin-alias plugin. If this field is not specified, the default value is:

    {
      entries: {
        'src': fileURLToPath(new URL('src', importMetaUrl)),
      },
    }

  • useNodeResolvePlugin: boolean: whether to use the @rollup/plugin-node-resolve plugin. If this field is not specified, the default value is true.

  • nodeResolvePluginOptions: object: the options for the @rollup/plugin-node-resolve plugin. If this field is not specified, the default value is: {}.

  • useCommonjsPlugin: boolean: whether to use the @rollup/plugin-commonjs plugin. If this field is not specified, the default value is true.

  • commonjsPluginOptions: object: the options for the @rollup/plugin-commonjs plugin. If this field is not specified, the default value is:

    {
      include: ['node_modules/**']
    }

  • useBabelPlugin: boolean: whether to use the @rollup/plugin-babel plugin. If this field is not specified, the default value is true.

  • babelPluginOptions: object: the options for the @rollup/plugin-babel plugin. If this field is not specified, the default value is:

    {
      babelHelpers: 'runtime',
      exclude: ['node_modules/**'],
      presets: [
        '@babel/preset-env',
      ],
      plugins: [
        '@babel/plugin-transform-runtime',
      ]
    }

    Note that if use the @rollup/plugin-babel plugin, you can also specify the configuration of Babel in the standard Babel configuration files, such as babel.config.js, .babelrc, etc.

  • terserOptions: object: the options for the @rollup/plugin-terser plugin. If this field is not specified, the default value is: {}. Whether to use the @rollup/plugin-terser plugin depends on the minify field of the options or the NODE_ENV environment variable.

  • useAnalyzerPlugin: boolean: whether to use the rollup-plugin-analyzer plugin. If this field is not specified, the default value is true.

  • analyzerOptions: object: the options for the rollup-plugin-analyzer plugin. If this field is not specified, the default value is:

    {
      hideDeps: true,
      limit: 0,
      summaryOnly: true,
    }

  • useVisualizerPlugin: boolean: whether to use the rollup-plugin-visualizer plugin. If this field is not specified, the default value is true.

  • visualizerPluginOptions: object: the options for the rollup-plugin-visualizer plugin. If this field is not specified, the default value is:

    {
      filename: './doc/${filenameBase}.visualization.html',
      gzipSize: true,
      brotliSize: true,
    }

    where the filenameBase is the basename of the compiled library file in the ./dist directory.

  • plugins: [object]: the additional Rollup plugins. If this field is not specified, the default value is an empty array.

If an ESM module has both default export and named exports, Rollup cannot handle it correctly. For example, the following is a source ESM module:

export { Foo, Bar };
export default Foo;

The rollup will translate it into the following codes:

exports.Foo = Foo;
exports.Bar = Bar;
exports.default = Foo;

However, a common-js consumer will use the module as follows:

const Foo = require('my-module');

which will cause an error. The correct usage should be

const Foo = require('my-module').default

But unfortunately, Rollup will translate the ESM default import as follows:

// source
import Foo from 'my-module';

// translated
const Foo = require('my-module');

Note that the above translation has no .default suffix, which will cause an error.

If you mix default and named exports in an ESM module, Rollup will generate a warning message as follows:

(!) Mixing named and default exports
https://rollupjs.org/configuration-options/#output-exports
The following entry modules are using named and default exports together:
src/index.js

Consumers of your bundle will have to use chunk.default to access their default export, which may not be what you want. Use `output.exports: "named"` to disable this warning.

The workaround is copied from the source code of the official rollup plugins. It makes the rollup option output.exports to 'named' and adds a simple footer statements to each CJS format bundle:

module.exports = Object.assign(exports.default, exports);

With this workaround, Rollup will transform mixed exports into the following form:

exports.Foo = Foo;
exports.Bar = Bar;
exports.default = Foo;
module.exports = Object.assign(exports.default, exports);

Thus, the caller can directly use the following methods to import the default export:

const Foo = require('my-module');
// or
import Foo from 'my-module';

See the following web pages for more details:

• Rollup Configuration Options: output.exports
• Issue #1961: Question regarding mixing default and named exports
• StackOverflow: Mixing default and named exports with Rollup
• Github Repository: rollup-patch-seamless-default-export

NOTE: In order to use this feature, you must specify the exports option to 'mixed' in the rollup.config.mjs file, i.e.,

import rollupBuilder from '@haixing_hu/rollup-builder';

export default rollupBuilder('MyLibrary', import.meta.url, { exports: 'mixed' });

Contributions are welcome! If you find any issues or have suggestions for improvements, please feel free to open an issue or create a pull request.

This project is licensed under the Apache 2.0 License. See the LICENSE file for details.