rollup-plugin-tree-shakeable

Install

``sh
$ npm i rollup-plugin-tree-shakeable
`

Usage

`js
import treeShakeable from 'rollup-plugin-tree-shakeable'

export default {
input: src/index.js,
output: {
dir: output,
format: esm,
},
plugins: [treeShakeable()],
}
`

Why?

Imagine you have code similar to this:

src/index.js:

`js
const withLogging =
fn =>
(...args) => {
console.log(Started call!)
try {
return fn(...args)
} finally {
console.log(Finished call!)
}
}

export const f1 = withLogging(/ ... /)
export const f2 = withLogging(/ ... /)
export const f3 = withLogging(/ ... /)
// ...
`

You might expect that if a user of your package writes
import { f1 } from 'your-package', then bundlers will
tree shake and
omit f1, f2, etc. from the final bundle. Unfortunately, bundlers will
generally include _all_ of your package's code in this case
(yes, even if you set "sideEffects": false in your package.json)
because withLogging is called at the "top-level" of your package and the
bundler cannot easily tell the call is side-effect free. There are _many_ other
code patterns that cause the same issue.

This plugin solves the problem by automatically adding
@__PURE__ annotations to all top-level
expressions in your code that prevent tree-shaking, with the assumption that
your package is actually pure,
but bundlers need a little convincing of that.

For example, for the code above, running it through this plugin would result in
the following code:

`js
const withLogging =
fn =>
(...args) => {
console.log(Started call!)
try {
return fn(...args)
} finally {
console.log(Finished call!)
}
}

export const f1 = / @__PURE__/ withLogging(/ ... /)
export const f2 = / @__PURE__/ withLogging(/ ... /)
export const f3 = / @__PURE__/ withLogging(/ ... /)
// ...
`

And if a user of your package writes import { f1 } from 'your-package', then
bundlers _will_ tree shake and strip out all functions other than f1` from the
final bundle.

> [!CAUTION]
>
> Only use this plugin if your package is actually tree-shakeable, meaning that
> each export would still function correctly if all the other exports were
> stripped out.
>
> This plugin does not give your package that property. It only _convinces_
> bundlers that this is the case.

Contributing

Stars are always welcome!

For bugs and feature requests,
please create an issue.

License

MIT
© Tomer Aberbach \
Apache 2.0 ©
Google