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# PostCSS Extend Rule [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS Logo" width="90" height="90" align="right">][postcss]
[![NPM Version][npm-img]][npm-url]
[![Build Status][cli-img]][cli-url]
[![Support Chat][git-img]][git-url]
[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 build tool:
```bash
npm install postcss-extend-rule --save-dev
```
#### Node
Use [PostCSS Extend Rule] to process your CSS:
```js
import postcssExtend from 'postcss-extend-rule';
postcssExtend.process(YOUR_CSS, /* processOptions */ /*, pluginOptions */);
```
#### PostCSS
Add [PostCSS] to your build tool:
```bash
npm install postcss --save-dev
```
Use [PostCSS Extend Rule] as a plugin:
```js
import postcss from 'gulp-postcss';
import postcssExtend from 'postcss-extend-rule';
postcss([
postcssExtend(/* pluginOptions */)
]).process(YOUR_CSS);
```
#### Webpack
Add [PostCSS Loader] to your build tool:
```bash
npm install postcss-loader --save-dev
```
Use [PostCSS Extend Rule] in your Webpack configuration:
```js
import postcssExtend from 'postcss-extend-rule';
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [
'style-loader',
{ loader: 'css-loader', options: { importLoaders: 1 } },
{ loader: 'postcss-loader', options: {
ident: 'postcss',
plugins: () => [
postcssExtend(/* pluginOptions */)
]
} }
]
}
]
}
}
```
#### Gulp
Add [Gulp PostCSS] to your build tool:
```bash
npm install gulp-postcss --save-dev
```
Use [PostCSS Extend Rule] in your Gulpfile:
```js
import postcss from 'gulp-postcss';
import postcssExtend from 'postcss-extend-rule';
gulp.task('css', () => gulp.src('./src/*.css').pipe(
postcss([
postcssExtend(/* pluginOptions */)
])
).pipe(
gulp.dest('.')
));
```
#### Grunt
Add [Grunt PostCSS] to your build tool:
```bash
npm install grunt-postcss --save-dev
```
Use [PostCSS Extend Rule] in your Gruntfile:
```js
import postcssExtend from 'postcss-extend-rule';
grunt.loadNpmTasks('grunt-postcss');
grunt.initConfig({
postcss: {
options: {
use: [
postcssExtend(/* pluginOptions */)
]
},
dist: {
src: '*.css'
}
}
});
```
## Options
### name
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;
}
```
### onFunctionalSelector
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 {}
```
### onRecursiveExtend
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;
}
```
### onUnusedExtend
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;
}
```
[cli-img]: https://img.shields.io/travis/jonathantneal/postcss-extend-rule.svg
[cli-url]: https://travis-ci.org/jonathantneal/postcss-extend-rule
[git-img]: https://img.shields.io/badge/support-chat-blue.svg
[git-url]: https://gitter.im/postcss/postcss
[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
[Gulp PostCSS]: https://github.com/postcss/gulp-postcss
[Grunt PostCSS]: https://github.com/nDmitry/grunt-postcss
[PostCSS]: https://github.com/postcss/postcss
[PostCSS Loader]: https://github.com/postcss/postcss-loader
[PostCSS Extend Rule]: https://github.com/jonathantneal/postcss-extend-rule