PostCSS Extend Rule [][postcss]

[![NPM Version][npm-img]][npm-url]
[][discord]

[PostCSS Extend Rule] lets you use the @extend at-rule and
[Functional Selectors] in CSS, following the speculative
[CSS Extend Rules Specification].

``pcss
%thick-border {
border: thick dotted red;
}

.serious-modal {
font-style: normal;
font-weight: bold;

@media (max-width: 240px) {
@extend .modal:hover;
}
}

.modal {
@extend %thick-border;

color: red;
}

.modal:hover:not(:focus) {
outline: none;
}

/ becomes /

.serious-modal {
font-style: normal;
font-weight: bold;
}

@media (max-width: 240px) {
.serious-modal:not(:focus) {
outline: none;
}
}

.modal {
border: thick dotted red;
color: red;
}

.modal:hover:not(:focus) {
outline: none;
}
`

Usage

Add [PostCSS Extend Rule] to your project:

`bash
npm install postcss postcss-extend-rule --save-dev
`

Use PostCSS Extend Rule to process your CSS:

`js
const postcssExtendRule = require('postcss-extend-rule');

postcssExtendRule.process(YOUR_CSS /, processOptions, pluginOptions /);
`

Or use it as a [PostCSS] plugin:

`js
const postcss = require('postcss');
const postcssExtendRule = require('postcss-extend-rule');

postcss([
postcssExtendRule(/ pluginOptions /)
]).process(YOUR_CSS /, processOptions /);
`

PostCSS Extend Rule runs in all Node environments, with special instructions for:

| Node | PostCSS CLI | Webpack | Create React App | Gulp | Grunt |
| --- | --- | --- | --- | --- | --- |

Options

$3

The name option determines the at-rule name being used to extend selectors.
By default, this name is extend, meaning @extend rules are parsed.

`js
postcssExtend({ name: 'postcss-extend' })
`

If the name option were changed to, say, postcss-extend, then only
@postcss-extend at-rules would be parsed.

`pcss
main {
@postcss-extend .some-rule;
}
`

$3

The onFunctionalSelector option determines how functional selectors should be
handled. Its options are:

- remove (default) removes any functional selector
- ignore ignores any functional selector and moves on
- warn warns the user whenever it encounters a functional selector
- throw throws an error if ever it encounters a functional selector

`js
postcssExtend({ onFunctionalSelector: 'remove' / default / })
`

`pcss
%this-will-be-removed {}
`

$3

The onRecursiveExtend option determines how recursive extend at-rules should
be handled. Its options are:

- remove (default) removes any recursive extend at-rules
- ignore ignores any recursive extend at-rules and moves on
- warn warns the user whenever it encounters a recursive extend at-rules
- throw throws an error if ever it encounters a recursive extend at-rules

`js
postcssExtend({ onRecursiveExtend: 'remove' / default / })
`

`pcss
.this-will-not-extend-itself {
@extend .this-will-not-extend-itself;
}
`

$3

The onUnusedExtend option determines how an unused extend at-rule should be
handled. Its options are:

- remove (default) removes any unused extend at-rule
- ignore ignores any unused extend at-rule and moves on
- warn warns the user whenever it encounters an unused extend at-rule
- throw throws an error if ever it encounters an unused extend at-rule

`js
postcssExtend({ onUnusedExtend: 'remove' / default / })
`

`pcss
main {
@extend .this-selector-does-not-exist-and-will-be-removed;
}
``

[git-img]: https://img.shields.io/badge/support-chat-blue.svg
[discord]: https://discord.gg/bUadyRwkJS
[npm-img]: https://img.shields.io/npm/v/postcss-extend-rule.svg
[npm-url]: https://www.npmjs.com/package/postcss-extend-rule

[CSS Extend Rules Specification]: https://jonathantneal.github.io/specs/css-extend-rule/
[Functional Selectors]: https://jonathantneal.github.io/specs/css-extend-rule/#functional-selector
[PostCSS]: https://github.com/postcss/postcss
[PostCSS Extend Rule]: https://github.com/csstools/postcss-extend-rule