Webpack SharedPackageModuleResolverPlugin

This is a webpack resolve plugin for a very specific case: When you're running multiple packages into a single project (a monorepo) and want one of the packages to rely on the dependencies of the other packages.

Reasoning

Consider this monorepo project structure:

packages/
├── appA/
│   ├── node_modules/
│   │   ├── [email protected]
│   │   └── [email protected]
│   └── app.js
│
├── appB/
│   ├── node_modules/
│   │   ├── [email protected]
│   │   └── [email protected]
│   └── app.js
│
└── lib/
    ├── card.js
    └── button.js

• appA uses react 17 and lodash 5
• appB uses react 15 and lodash 5
• lib is a package of reusable components
• appA/app.js imports lib/card.js
• appB/app.js also imports lib/card.js
• lib/card.js imports react and lodash

The outcome without this plugin:

• lib/ has to install its own dependencies or rely on the root node_modules folder
• in the case of react, appA and appB are using different versions, so lib/ will be incompatible with one of them.
• in the case of lodash, appA and appB are using the same version, but lib/ can't use them. we'll endup with two copies of the same lodash version in the bundle

The outcome with this plugin:

• lib/ does not have to install its own dependencies
• when requested by appA, lib/* will resolve its modules from appA
• when requested by appB, lib/* will resolve its modules from appB
• we solve both issues: no duplicated lodash and no conflicting react versions

Instalation

npm install --save-dev shared-package-module-resolver-plugin

Usage

import SharedPackageModuleResolverPlugin from 'shared-package-module-resolver-plugin'

module.exports = {
  ...
  resolve: {
    // note this is a resolver plugin, so it goes inside resolve.plugins, not inside the main plugin object
    plugins: [new SharedPackageModuleResolverPlugin({
      packagesPath: path.join(__dirname, 'packages') // This has to be the absolute path!,
      sharedPackage: 'lib', // do not add slashes or anything else. just the name of the package
    })]
  }
}