# `rollup-plugin-pure`

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> Automatically add `/* #__PURE__ */` annotations before definition functions

- [▶️  Online playground](https://stackblitz.com/github/danielroe/rollup-plugin-pure/tree/main/playground)

## Features

- ⚡️ avoids end-users bundling unused code

## How it works

Definition functions (for example, in Vue with `defineComponent`) are increasingly common but do not play nice with tree-shaking. It's not possible to tell whether or not a function call which receives an object can be tree-shaken from a build, as it's possible there might be side effects.

Rollup supports `/* @__PURE__ */` annotations to declare this from a library author's point of view, but it can be tricky when we know that _every_ occurrence of a function call is pure.

This plugin will automatically inject the annotation before any occurrence of the function call, as well as injecting `/* @__NO_SIDE_EFFECTS__ */` annotations in front of function declarations.

## Installation

Install and add `rollup-plugin-pure` to your Vite or Rollup config.

```bash
pnpm add -D rollup-plugin-pure
```

```js
import { PluginPure } from 'rollup-plugin-pure'
import { defineConfig } from 'vite'

export default defineConfig({
  plugins: [
    PluginPure({
      functions: ['defineComponent', /^define(Page|Meta)$/],
      include: [/(?<!im)pure\.js$/],
      // exclude: [],
      // sourcemap: true,
    }),
  ],
})
```

## 💻 Development

- Clone this repository
- Enable [Corepack](https://github.com/nodejs/corepack) using `corepack enable`
- Install dependencies using `pnpm install`
- Stub module with `pnpm dev:prepare`
- Run `pnpm dev` to start [playground](./playground) in development mode

## License

Made with ❤️

Published under the [MIT License](./LICENCE).

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