rollup-plugin-cjs-check

1.0.3 verified Mon Apr 27 auth: no javascript

A Rollup plugin that automatically verifies CommonJS output compatibility with Node.js's cjs-module-lexer. Currently at v1.0.3, with stable release cadence. It analyzes the generated CJS bundle and compares the exports detected by Rollup against those that cjs-module-lexer would detect, flagging mismatches that cause broken named imports in Node.js ESM. Unlike manual testing, this provides automated CI enforcement. Requires Rollup >=1.20.0 and Node >=14.0.0.

Common errors

error RollupError: [rollup-plugin-cjs-check] Export 'MyExport' is not detected by cjs-module-lexer ↓

cause Rollup detected an export that cjs-module-lexer cannot parse, likely due to dynamic export patterns or re-exports.

fix

Use static export syntax or output format 'es' for full ESM compatibility.

error Error: Expected output format to be 'cjs' but got 'es' ↓

cause Plugin was used with a non-CJS output format, causing the check to be skipped (but may warn).

fix

Ensure the Rollup configuration uses format: 'cjs'.

Warnings

gotcha Plugin only works when output format is 'cjs'. Using with other formats silently skips checking. ↓

fix Ensure your Rollup output format is 'cjs'.

gotcha Plugin does not fix mismatched exports; it only reports them. Manual adjustment of Rollup configuration or code may be needed. ↓

fix Review the reported mismatches and adjust named exports or use 'output.exports: 'named'' configuration.

Install

npm install rollup-plugin-cjs-check

yarn add rollup-plugin-cjs-check

pnpm add rollup-plugin-cjs-check

Imports

default

wrong

const { cjsCheck } = require('rollup-plugin-cjs-check')

correct

import cjsCheck from 'rollup-plugin-cjs-check'

Default export only; named export does not exist.

cjsCheck

wrong

import { cjsCheck } from 'rollup-plugin-cjs-check'

correct

import cjsCheck from 'rollup-plugin-cjs-check'

This is the default import. Named import 'cjsCheck' is a common mistake.

type CjsCheckOptions
```
import type { CjsCheckOptions } from 'rollup-plugin-cjs-check'
```
TypeScript type exported for plugin options; not a runtime export.

Quickstart

Basic Rollup configuration using the cjs-check plugin to validate CJS exports.

// rollup.config.js
import cjsCheck from 'rollup-plugin-cjs-check';

export default {
  input: 'src/index.js',
  output: {
    dir: 'output',
    format: 'cjs',
  },
  plugins: [
    cjsCheck(),
  ],
};