rollup-plugin-peer-deps-external/README.md

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# Rollup Plugin Peer Deps External
Automatically externalize `peerDependencies` in a `rollup` bundle.
Also optionally externalize `dependencies` in a `rollup` bundle.

## Motivation
When bundling a library using [`rollup`](https://github.com/rollup/rollup), we generally want to keep from including  [`peerDependencies`](https://nodejs.org/en/blog/npm/peer-dependencies/) since they are expected to be  provided by the consumer of the library. By excluding these dependencies, we keep bundle size down and avoid bundling duplicate dependencies.

We can achieve this using the rollup [`external`](https://github.com/rollup/rollup/wiki/JavaScript-API#external) configuration option, providing it a list of the peer dependencies to exclude from the bundle. This plugin automates the process, automatically adding a library's `peerDependencies` to the `external` configuration.

## Module paths
This plugin is compatible with module path format applied by, for example, [`babel-plugin-lodash`](https://github.com/lodash/babel-plugin-lodash). For any module name in `peerDependencies`, all paths beginning with that module name will also be added to `external`.

E.g.: If `lodash` is in `peerDependencies`, an import of `lodash/map` would be added to externals.

## Installation
```bash
npm install --save-dev rollup-plugin-peer-deps-external
```

## Usage
```javascript
// Add to plugins array in rollup.config.js
import peerDepsExternal from 'rollup-plugin-peer-deps-external';

export default {
  plugins: [
    // Preferably set as first plugin.
    peerDepsExternal(),
  ],
}
```

## Options
### packageJsonPath
If your `package.json` is not in the current working directory you can specify the path to the file
```javascript
// Add to plugins array in rollup.config.js
import peerDepsExternal from 'rollup-plugin-peer-deps-external';

export default {
  plugins: [
    // Preferably set as first plugin.
    peerDepsExternal({
      packageJsonPath: 'my/folder/package.json'
    }),
  ],
}
```

### includeDependencies
Sometimes it's necessary to include a package as a direct dependency instead of a peer dependency. This can happen if your package has a very specific requirement on the dependency and cannot accecpt another version. In this case set `includeDependencies` to `true` and all of your packages dependencies will also be included as externals

```javascript
// Add to plugins array in rollup.config.js
import peerDepsExternal from 'rollup-plugin-peer-deps-external';

export default {
  plugins: [
    // Preferably set as first plugin.
    peerDepsExternal({
      includeDependencies: true,
    }),
  ],
}
```