Prebundle-esm

Prebundle Node.js dependencies, output a single js file, a package.json file and the dts files.

Based on ncc, esbuild and rollup-plugin-dts.

Motivation

prebundle-esm vs prebundle:

• Use esbuild to build esm package.

Prebundle is used to:

• Reduce dependencies of core packages, install faster.
• Improve stability by locking the sub-dependency version .
• Fix peer dependency warning of some packages.

Command

Run following command to prebundle all dependencies:

npx prebundle-esm

Run following command to prebundle single dependencies:

npx prebundle-esm <pkgName>

# For example, prebundle commander
npx prebundle-esm commander

Dependency Config

Supported dependency config:

esm

set esbuildFormat to esm to build esm package.

// prebundle.config.mjs
/** @type {import('prebundle-esm').Config} */
export default {
  dependencies: [
    {
      name: 'foo',
      target: 'es2015',
    },
    {
      name: '@aws-sdk/client-s3',
      esbuildPlatform: 'node',
      // re-export all `modules.exports`.
      esbuildExportCjsNamedExport: true,
      esbuildExportStarAsDefault: false,
      esbuildFormat: 'esm',
    },
  ],
};

But when your package is mixing cjs and esm, you'd better choose esbuildFormat: 'cjs', please see https://dev.to/marcogrcr/nodejs-and-esbuild-beware-of-mixing-cjs-and-esm-493n for details.

externals

Externals to leave as requires of the build.

// prebundle.config.mjs

/** @type {import('prebundle-esm').Config} */
export default {
  dependencies: [
    {
      name: 'foo',
      externals: {
        webpack: '../webpack',
      },
    },
  ],
};

You can also configure externals for all packages like this:

// prebundle.config.mjs
export default {
  externals: {
    webpack: '../webpack',
  },
  dependencies: [{ name: 'foo' }, { name: 'foo' }],
};

dtsExternals

Externals for dts.

// prebundle.config.mjs
export default {
  dependencies: [
    {
      name: 'foo',
      dtsExternals: ['webpack'],
    },
  ],
};

minify

Whether to minify the code, default false.

// prebundle.config.mjs
export default {
  dependencies: [
    {
      name: 'foo',
      minify: false,
    },
  ],
};

packageJsonField

Copy extra fields from original package.json to target package.json.

// prebundle.config.mjs
export default {
  dependencies: [
    {
      name: 'foo',
      packageJsonField: ['options'],
    },
  ],
};

Following fields will be copied by default:

• name
• author
• version
• funding
• license
• types
• typing
• typings

beforeBundle

Callback before bundle.

// prebundle.config.mjs
export default {
  dependencies: [
    {
      name: 'foo',
      beforeBundle(task) {
        console.log('do something');
      },
    },
  ],
};

emitFiles

Emit extra entry files to map imports.

// prebundle.config.mjs
export default {
  dependencies: [
    {
      name: 'foo',
      emitFiles: [
        {
          path: 'foo.js',
          content: `module.exports = require('./').foo;`,
        },
      ],
    },
  ],
};

ignoreDts

Ignore the original .d.ts declaration file, then generate a fake .d.ts file.

This can be used to reduce file size for the packages that do not require type definitions, such as webpack plugin.

// prebundle.config.mjs
export default {
  dependencies: [
    {
      name: 'foo',
      ignoreDts: true,
    },
  ],
};

target

Target ECMAScript version, default es2021.

// prebundle.config.mjs
export default {
  dependencies: [
    {
      name: 'foo',
      target: 'es2015',
    },
  ],
};

prettier

Whether to prettier the code and strip comments, default false.

// prebundle.config.mjs
export default {
  prettier: true,
};