rollup-plugin-merge

0.2.1 verified Mon Apr 27 auth: no javascript

A Rollup plugin to merge multiple JSON files into a single JSON output during the build process. Current stable version is 0.2.1, with no recent updates and a small scope. It supports recursive merging, watching for changes, and optional pretty-printing. Unlike general-purpose merge tools, it integrates directly into Rollup's plugin system. Use with caution due to infrequent maintenance.

Common errors

error Error [ERR_REQUIRE_ESM]: require() of ES Module not supported. ↓

cause Package is ESM-only, but CommonJS require() is used.

fix

Use import instead: import merge from 'rollup-plugin-merge'

error TypeError: merge is not a function ↓

cause Importing the plugin incorrectly (e.g., named import instead of default).

fix

Use default import: import merge from 'rollup-plugin-merge'

error Plugin error: Cannot find module 'rollup-plugin-merge' ↓

cause Package not installed or missing from node_modules.

fix

Run npm install rollup-plugin-merge --save-dev

Warnings

gotcha The 'recursive' option is misspelled as 'recurisve' in the documentation; use 'recursive' (correct spelling) in config. ↓

fix Use 'recursive' instead of 'recurisve' in the options object.

deprecated No updates since 2019; may not work with latest Rollup versions (v3+). ↓

fix Consider alternatives like @rollup/plugin-json or manual merging.

gotcha Plugin uses CJS internally, but package is ESM-only; may cause issues in mixed module environments. ↓

fix Ensure your project is configured for ESM imports.

gotcha Watching ('watch' option) only copies files on start; does not trigger full rebuild. ↓

fix Set 'watch: true' only if you want initial copy; use Rollup's watch mode for rebuilds.

Install

npm install rollup-plugin-merge

yarn add rollup-plugin-merge

pnpm add rollup-plugin-merge

Imports

default

wrong

const merge = require('rollup-plugin-merge')

correct

import merge from 'rollup-plugin-merge'

ESM-only; does not support CommonJS require.

MergeOptions
```
import type { MergeOptions } from 'rollup-plugin-merge'
```
TypeScript users; the package does not ship types, but you can define your own for options.

rollup-plugin-merge

wrong

import { default as merge } from 'rollup-plugin-merge'

correct

import merge from 'rollup-plugin-merge'

Default import is the only way; no named exports.

Quickstart

Example of merging two JSON files into a single output during Rollup build with recursive merge and prettification.

import merge from 'rollup-plugin-merge';

export default {
  input: 'src/index.js',
  output: {
    file: 'dist/bundle.js',
    format: 'iife',
    name: 'app'
  },
  plugins: [
    merge({
      input: ['src/file1.json', 'src/file2.json'],
      output: 'dist/config.json',
      recursive: true,
      prettify: true,
      watch: true
    })
  ]
};