rollup-plugin-node-externals

A Rollup plugin that automatically declares NodeJS built-in modules as external. Also handles npm dependencies, devDependencies, peerDependencies and optionalDependencies.

Works in npm/yarn/pnpm/lerna monorepos too!

Why you need this

(click to expand)

By default, Rollup doesn't know a thing about NodeJS, so trying to bundle simple things like import path from 'node:path' in your code generates an Unresolved dependencies warning.

The solution here is quite simple: you must tell Rollup that the node:path module is in fact external. This way, Rollup won't try to bundle it in and rather leave the import statement as is (or translate it to a require() call if bundling for CommonJS).

However, this must be done for each and every NodeJS built-in you happen to use in your program: node:path, node:os, node:fs, node:url, etc., which can quickly become cumbersome when done manually.

So the primary goal of this plugin is simply to automatically declare all NodeJS built-in modules as external.

As an added bonus, this plugin will also allow you to declare your dependencies (as per your local or monorepo package.json file(s)) as external.

Installation

Use your favorite package manager. Mine is npm.

npm install --save-dev rollup-plugin-node-externals

Usage

Import

The plugin is available both as the default export and as a named export:

import nodeExternals from 'rollup-plugin-node-externals'

and

import { nodeExternals } from 'rollup-plugin-node-externals'

will both work.

Options

You generally want to have your runtime dependencies (those that will be imported/required at runtime) listed under dependencies in package.json, and your development dependencies (those that should be bundled in by Rollup) listed under devDependencies.

If you follow this simple rule, then the default settings are just what you need:

// rollup.config.js

export default {
  ...
  plugins: [
    nodeExternals(),
  ]
}

This will bundle your devDependencies in while leaving your dependencies, peerDependencies and optionalDependencies external.

Should the defaults not suit your case, here is the full list of options.

import nodeExternals from 'rollup-plugin-node-externals'

export default {
  ...
  plugins: [
    nodeExternals({

      // Make node builtins external. Default: true.
      builtins?: boolean

      // node: prefix handing for importing Node builtins. Default: 'add'.
      builtinsPrefix?: 'add' | 'strip' | 'ignore'

      // The path(s) to your package.json. See below for default.
      packagePath?: string | string[]

      // Make pkg.dependencies external. Default: true.
      deps?: boolean

      // Make pkg.devDependencies external. Default: false.
      devDeps?: boolean

      // Make pkg.peerDependencies external. Default: true.
      peerDeps?: boolean

      // Make pkg.optionalDependencies external. Default: true.
      optDeps?: boolean

      // Modules to force include in externals. Default: [].
      include?: string | RegExp | (string | RegExp)[]

      // Modules to force exclude from externals. Default: [].
      exclude?: string | RegExp | (string | RegExp)[]
    })
  ]
}

builtins?: boolean = true

Set the builtins option to false if you'd like to use some shims/polyfills for those. You'll most certainly need an other plugin as well.

builtinsPrefix?: 'add' | 'strip' | 'ignore' = 'add'

How to handle the node: scheme used in recent versions of Node (i.e., import path from 'node:path').

• If add (the default, recommended), the node: prefix is always added. In effect, this homogenizes all your imports of Node builtins to their prefixed version.
• If strip, the prefix is always removed. In effect, this homogenizes all your imports of Node builtins to their unprefixed version.
• ignore will simply leave all builtins imports as written in your code.

Note that prefix handling is always applied, regardless of the builtins options being enabled or not.

packagePath?: string | string[] = []

If you're working with monorepos, the packagePath option is made for you. It can take a path, or an array of paths, to your package.json file(s). If not specified, the default is to start with the current directory's package.json then go up scan for all package.json files in parent directories recursively until either the root git directory is reached or until no other package.json can be found.

deps?: boolean = true
devDeps?: boolean = false
peerDeps?: boolean = true
optDeps?: boolean = true

Set the deps, devDeps, peerDeps and optDeps options to false to prevent the corresponding dependencies from being externalized, therefore letting Rollup bundle them with your code.

include?: string | RegExp | (string | RegExp)[] = []

Use the include option to force certain dependencies into the list of externals, regardless of other settings:

nodeExternals({
  deps: false,                // Deps will be bundled in
  include: 'fsevents'         // Except for fsevents
})

exclude?: string | RegExp | (string | RegExp)[] = []

Conversely, use the exclude option to remove certain dependencies from the list of externals, regardless of other settings:

nodeExternals({
  deps: true,                 // Keep deps external
  exclude: 'electron-reload'  // Yet we want `electron-reload` bundled in
})

Notes

1/ This plugin is smart

• Falsy values in include and exclude are silently ignored. This allows for conditional constructs like exclude: process.env.NODE_ENV === 'production' && 'my-prod-only-dep'.
• Subpath imports are supported with regexes, meaning that include: /^lodash/ will externalize lodash and also lodash/map, lodash/merge, etc.

2/ This plugin is not that smart

It uses an exact match against your imports as written in your code, so if your are using some kind of path substitution, eg.:

// In your code, say '@/' is mapped to some directory:
import something from '@/mylib'

and you don't want mylib bundled in, then write:

// In rollup.config.js:
nodeExternals({
    include: '@/mylib'
})

3/ Order matters

If you're also using @rollup/plugin-node-resolve, make sure this plugin comes before it in the plugins array:

import nodeExternals from 'rollup-plugin-node-externals'
import nodeResolve from '@rollup/plugin-node-resolve'

export default {
  ...
  plugins: [
    nodeExternals(),
    nodeResolve(),
  ]
}

As a general rule of thumb, you might want to always make this plugin the first one in the plugins array.

4/ Rollup rules

Rollup's own external configuration option always takes precedence over this plugin. This is intentional.

Breaking changes

Breaking changes in version 7

• This package now supports the latest release of any major version that is supported by Node.js itself.
• The undocumented externals named export has been removed.

Breaking changes in previous versions

Previous versions -- click to expand

Breaking changes in version 6

• This package is now esm-only and requires NodeJS v16+.
  If you need CommonJS or older NodeJS support, please stick to v5.
• This plugin now has a peer-dependency on Rollup ^3.0.0 || ^4.0.0.
  If you need Rollup 2 support, please stick to v5.

Breaking changes in version 5

• In previous versions, the devDeps option defaulted to true.
  This was practical, but often wrong: devDependencies are meant just for that: being used when developping. Therefore, the devDeps option now defaults to false, meaning Rollup will include them in your bundle.
• As anticipated since v4, the builtinsPrefix option now defaults to 'add'.
• The deprecated prefixedBuiltins option has been removed. Use builtinsPrefix instead.
• rollup-plugin-node-externals no longer depends on the Find-Up package (while this is not a breaking change per se, it can be in some edge situations).
• The plugin now has a peer dependency on rollup ^2.60.0 || ^3.0.0.

Breaking changes in version 4

• In previous versions, the deps option defaulted to false.
  This was practical, but often wrong: when bundling for distribution, you want your own dependencies to be installed by the package manager alongside your package, so they should not be bundled in the code. Therefore, the deps option now defaults to true.
• Now requires Node 14 (up from Node 12 for previous versions).
• Now has a peer dependency on rollup ^2.60.0.

Licence

MIT