120 lines
3.7 KiB
Markdown
120 lines
3.7 KiB
Markdown
# PostCSS Custom Selectors [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS Logo" width="90" height="90" align="right">][PostCSS]
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[<img alt="npm version" src="https://img.shields.io/npm/v/postcss-custom-selectors.svg" height="20">][npm-url] [<img alt="CSS Standard Status" src="https://cssdb.org/images/badges/custom-selectors.svg" height="20">][css-url] [<img alt="Build Status" src="https://github.com/csstools/postcss-plugins/workflows/test/badge.svg" height="20">][cli-url] [<img alt="Discord" src="https://shields.io/badge/Discord-5865F2?logo=discord&logoColor=white">][discord]
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```bash
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npm install postcss-custom-selectors --save-dev
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```
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[PostCSS Custom Selectors] lets you define `@custom-selector` in CSS following the [Custom Selectors Specification].
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```pcss
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@custom-selector :--heading h1, h2, h3;
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article :--heading + p {
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margin-top: 0;
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}
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/* becomes */
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article :is(h1, h2, h3) + p {
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margin-top: 0;
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}
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```
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## Usage
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Add [PostCSS Custom Selectors] to your project:
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```bash
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npm install postcss postcss-custom-selectors --save-dev
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```
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Use it as a [PostCSS] plugin:
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```js
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const postcss = require('postcss');
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const postcssCustomSelectors = require('postcss-custom-selectors');
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postcss([
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postcssCustomSelectors(/* pluginOptions */)
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]).process(YOUR_CSS /*, processOptions */);
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```
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[PostCSS Custom Selectors] runs in all Node environments, with special
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instructions for:
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- [Node](INSTALL.md#node)
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- [PostCSS CLI](INSTALL.md#postcss-cli)
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- [PostCSS Load Config](INSTALL.md#postcss-load-config)
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- [Webpack](INSTALL.md#webpack)
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- [Next.js](INSTALL.md#nextjs)
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- [Gulp](INSTALL.md#gulp)
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- [Grunt](INSTALL.md#grunt)
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## Options
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### preserve
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The `preserve` option determines whether the original notation
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is preserved. By default, it is not preserved.
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```js
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postcssCustomSelectors({ preserve: true })
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```
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```pcss
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@custom-selector :--heading h1, h2, h3;
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article :--heading + p {
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margin-top: 0;
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}
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/* becomes */
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@custom-selector :--heading h1, h2, h3;
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article :is(h1, h2, h3) + p {
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margin-top: 0;
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}
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article :--heading + p {
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margin-top: 0;
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}
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```
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## Modular CSS Processing
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If you're using Modular CSS such as, CSS Modules, `postcss-loader` or `vanilla-extract` to name a few, you'll probably
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notice that custom selectors are not being resolved. This happens because each file is processed separately so
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unless you import the custom selector definitions in each file, they won't be resolved.
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To overcome this, we recommend using the [PostCSS Global Data](https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-global-data#readme)
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plugin which allows you to pass a list of files that will be globally available. The plugin won't inject any extra code
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in the output but will provide the context needed to resolve custom selectors.
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For it to run it needs to be placed before the [PostCSS Custom Selectors] plugin.
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```js
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const postcss = require('postcss');
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const postcssCustomSelectors = require('postcss-custom-selectors');
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const postcssGlobalData = require('@csstools/postcss-global-data');
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postcss([
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postcssGlobalData({
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files: [
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'path/to/your/custom-selectors.css'
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]
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}),
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postcssCustomSelectors(/* pluginOptions */)
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]).process(YOUR_CSS /*, processOptions */);
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```
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[cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test
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[css-url]: https://cssdb.org/#custom-selectors
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[discord]: https://discord.gg/bUadyRwkJS
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[npm-url]: https://www.npmjs.com/package/postcss-custom-selectors
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[PostCSS]: https://github.com/postcss/postcss
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[PostCSS Custom Selectors]: https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-custom-selectors
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[Custom Selectors Specification]: https://drafts.csswg.org/css-extensions/#custom-selectors
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