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0.1.3 • Public • Published


Transpile Create-React-App imports in Lerna projects.

This package overrides the Webpack configuration of Create-React-App projects in a Lerna repo.

⚠️ Please Note

As with packages like React-App-Rewired...

Using babel-loader-lerna-cra breaks the "guarantees" that Create React App provides. That is to say, you now "own" the configs. No support will be provided. Proceed with caution.

"Stuff can break" — Dan Abramov

The Problem

Many people are trying to use Create-React-App in a Lerna repo with a project structure similar to this:

├── lerna.json
├── package.json
└── packages
    ├── comp-a
    ├── comp-b
    ├── my-react-app-1
    │   └── comp-a
    └── my-react-app-2
        ├── comp-a
        └── comp-b

When running the React App, errors like these show up:

Error: You may need an appropriate loader to handle this file.
Failed to compile.
SyntaxError: .../monorepo-react/packages/comp-button/src/index.js: Unexpected token (4:4)
  2 |
  3 | const Button = (type = 'button', children, onClick }) => (
> 4 |     <div>
    |     ^
  5 |       <button type={type} className="button" onClick={onClick}>
  6 |         {children}
  7 |       </button>

These errors show up because the Webpack config in your Create-React-App does not look outside the React App's ./src directory for additional import dirs. In fact, how could it? It has no idea how you would configure your monorepo.

The Solution

This module (babel-loader-lerna-cra) allows you to configure Webpack config overrides in your Lerna project's package.json file; allowing babel to transpile imported Lerna packages using dev and prod.


  1. Install babel-loader-lerna-cra in your Lerna repo:

    npm i -D babel-loader-lerna-cra
  2. Configure the package.json in your Lerna root:

        "name": "root",
        "private": true,
        "devDependencies": {
            "babel-learna-loader-cra": "*"
        "babel-loader-lerna-cra": {
            "imports": "packages/comp-*/src",
            "apps":  "packages/*react-app*"
    • imports - glob pattern for imports that require transpiling
    • apps - glob pattern for app that need overriding
  3. Boostrap your React Apps with Webpack overrides:

    Note: you MUST complete step two first.

    npx babel-loader-lerna-cra

    You should see this output:

    babel-lerna-loader-cra: bootstraping...
    babel-lerna-loader-cra: config = {
      lernaRoot: '../monorepo-react',
      settings: {
        imports: 'packages/comp-*/src',
        apps: 'packages/*react-app*'
      apps: [
      imports: [
    babel-lerna-loader-cra: copying: my-react-app-1/... =>
    babel-lerna-loader-cra: copying: my-react-app-1/... webpack.config.replacement.js =>
    babel-lerna-loader-cra: copying: my-react-app-1/... =>
    babel-lerna-loader-cra: copying: my-react-app-1/... webpack.config.replacement.js =>
    babel-lerna-loader-cra: copying: my-react-app-2/... =>
    babel-lerna-loader-cra: copying: my-react-app-2/... webpack.config.replacement.js =>
    babel-lerna-loader-cra: copying: my-react-app-2/... =>
    babel-lerna-loader-cra: copying: my-react-app-2/... webpack.config.replacement.js =>

    Note: you will need to bootstrap again when:

    1. Installing packages in CI
    2. When a new create-react-app is added

Related issues


npm i babel-loader-lerna-cra

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