rehype-postcss

rehype plugin to process <style> nodes and elements containing a style attribute with PostCSS.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • unified().use(rehypePostCSS[, options])
• Types
• Compatibility
• Related
• License

What is this?

This package is a unified (rehype) plugin to process <style> nodes and elements with a style attribute using PostCSS.

unified is a project that transforms content with abstract syntax trees (ASTs). rehype adds support for HTML to unified. hast is the HTML AST that rehype uses. This is a rehype plugin that runs PostCSS on <style> elements and other elements that have a style attribute.

When should I use this?

In most cases running PostCSS with postcss-html syntax through CLI or with your build tool should be enough.

When it's not, this plugin helps you run PostCSS through nodes contextually, run on fragments etc.

Specifically, the plugin was written to apply CSS Modules in context of the parent element what would not be possible to do in another way.

Install

This package is ESM only. In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm:

npm install rehype-postcss

In Deno with esm.sh:

import rehypePostCSS from 'https://esm.sh/rehype-postcss@0.1'

In browsers with esm.sh:

<script type="module">
  import rehypePostCSS from 'https://esm.sh/rehype-postcss@6?bundle'
</script>

Use

Say we have the following file example.html:

<style>
  a {
    display: flex;
  }
</style>

And our module example.js looks as follows:

import { read } from 'to-vfile'
import { rehype } from 'rehype'
import rehypePostCSS from 'rehype-postcss'

const file = await rehype()
  .data('settings', { fragment: true })
  .use(rehypePostCSS, {
    plugins: [
      autoprefixer({ overrideBrowserslist: ['ie >= 10'] }),
    ],
  })
  .process(await read('example.html'))

console.log(String(file))

Now, running node example.js yields:

<style>
  a {
    display: -ms-flexbox;
    display: flex;
  }
</style>

API

This package exports no identifiers. The default export is rehypePostCSS.

unified().use(rehypePostCSS[, options])

Runs PostCSS.

options

Configuration (optional).

options.plugins

A list of plugins to run with the PostCSS processor. This list is passed directly; the whole process can be imagined simply like in the example.

👉 Note: If options.plugins is not passed or is an empty array, the plugin would look for a PostCSS config in the current working directory.

If such a config could not be found, an error is thrown.

options.options

Processor options. The object would complement defaults and passed to the process call.

The initial default options are:

{
  from: 'path of the source file',
  map: false,
}

👉 Note: Source maps (map option) are turned off by default.

If you are going to use source maps, turn it on as well as pass to option to let the processor rewrite URLs properly. When the from option can be discovered from the file, there is no way to know where the result is going to be saved.

options.test

Test to define which elements should be processed. The test must be a function; if it's anything else, it is ignored. The default (no test) is to process all <style> elements and any element with a style attribute. If the option is passed, it will be filtering out from the list of selected nodes by the default test.

Types

This package is not typed with TypeScript. It can be though if you send a PR or when I have some extra time.

Compatibility

The project should be compatible with Node.js 12.20+, 14.14+, and 16.0+ but the compatibility is not tested.

Related

This plugin was inspired by posthtml-postcss.

License

MIT © Viktor Yakubiv