babel-loader-lerna-cra

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 https://twitter.com/dan_abramov/status/1045809734069170176

The Problem

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

my-lerna-project/
├── 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.

../comp-button/src/index.js
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.

Usage

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: [
       '../packages/my-react-app-1',
       '../packages/my-react-app-2'
     ],
     imports: [
       '../packages/comp-a/src',
       '../packages/comp-a/src',
       '../packages/comp-b/src'
       ]
   }
   babel-lerna-loader-cra: copying: my-react-app-1/... webpack.config.dev.js => backup.webpack.config.prod.js
   babel-lerna-loader-cra: copying: my-react-app-1/... webpack.config.replacement.js => webpack.config.dev.js
   babel-lerna-loader-cra: copying: my-react-app-1/... webpack.config.prod.js => backup.webpack.config.prod.js
   babel-lerna-loader-cra: copying: my-react-app-1/... webpack.config.replacement.js => webpack.config.prod.js
   babel-lerna-loader-cra: copying: my-react-app-2/... webpack.config.dev.js => backup.webpack.config.prod.js
   babel-lerna-loader-cra: copying: my-react-app-2/... webpack.config.replacement.js => webpack.config.dev.js
   babel-lerna-loader-cra: copying: my-react-app-2/... webpack.config.prod.js => backup.webpack.config.prod.js
   babel-lerna-loader-cra: copying: my-react-app-2/... webpack.config.replacement.js => webpack.config.prod.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

• babel/babel-loader#377
• facebook/create-react-app#4161
• facebook/create-react-app#1333