rollup-plugin-bundle-esm

0.1.1 verified Mon Apr 27 auth: no javascript

A Rollup plugin that automatically bundles only ESM-only dependencies while leaving CommonJS-compatible packages external, optimizing bundle size and reducing edge cases. Current stable version is 0.1.1 (released 2022, no recent updates). Key differentiator: solves the dual-packaging problem for environments without ESM support (e.g., Electron) by specifically targeting ESM packages for inlining, unlike general-purpose resolve plugins that bundle everything. Compatible with Rollup 3+; requires @rollup/plugin-node-resolve and @rollup/plugin-commonjs as companion plugins.

Common errors

error Error: Cannot find module 'rollup-plugin-bundle-esm' ↓

cause Package not installed or incorrect import path.

fix

Run npm install --save-dev rollup-plugin-bundle-esm and ensure import path is correct.

error TypeError: bundleESM is not a function ↓

cause Importing named export instead of default export.

fix

Use import bundleESM from 'rollup-plugin-bundle-esm' instead of import { bundleESM } from ....

error Error: ESM package 'x' was treated as external but should be bundled ↓

cause Plugin incorrectly classifies package as CommonJS due to missing 'type' field.

fix

Manually specify 'forceBundle' for that package: bundleESM({ forceBundle: ['x'] }).

Warnings

gotcha Plugin may not correctly detect package format if package.json is malformed or missing 'type' field. Assumes no 'type' field means CommonJS. ↓

fix Ensure all dependencies have a 'type' field in their package.json; use 'forceBundle' option to override.

gotcha The plugin must be placed after nodeResolve() in the Rollup plugin list to work correctly. ↓

fix Order plugins: commonjs() first, then nodeResolve(), then bundleESM().

gotcha forceBundle option uses the same signature as rollup.external, which may cause confusion between including vs excluding. ↓

fix Use forceBundle to force bundling of specific packages; do not confuse with external option.

deprecated Package has not been updated since v0.1.1 (released 2022); may lack compatibility with latest Rollup versions. ↓

fix Consider alternative plugins or manual external configuration.

Install

npm install rollup-plugin-bundle-esm

yarn add rollup-plugin-bundle-esm

pnpm add rollup-plugin-bundle-esm

Imports

default

wrong

import { bundleESM } from 'rollup-plugin-bundle-esm'

correct

import bundleESM from 'rollup-plugin-bundle-esm'

The plugin exports a single default function; named import does not work.

default

wrong

const { bundleESM } = require('rollup-plugin-bundle-esm')

correct

const bundleESM = require('rollup-plugin-bundle-esm')

CommonJS require gets the default export as the whole module.

BundleESMOptions

wrong

import { BundleESMOptions } from 'rollup-plugin-bundle-esm'

correct

import type { BundleESMOptions } from 'rollup-plugin-bundle-esm'

Type import for TypeScript users; the type is not exported as a value.

Quickstart

Configures Rollup to bundle only ESM dependencies, leaving CommonJS packages external.

import commonjs from '@rollup/plugin-commonjs';
import { nodeResolve } from '@rollup/plugin-node-resolve';
import { defineConfig } from 'rollup';
import bundleESM from 'rollup-plugin-bundle-esm';

export default defineConfig({
  output: {
    format: 'commonjs',
    dir: 'dist',
  },
  input: 'index.js',
  plugins: [commonjs(), nodeResolve(), bundleESM()],
});