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https://github.com/postcss/postcss-loader
PostCSS loader for webpack
https://github.com/postcss/postcss-loader
Last synced: 3 months ago
JSON representation
PostCSS loader for webpack
- Host: GitHub
- URL: https://github.com/postcss/postcss-loader
- Owner: webpack-contrib
- License: mit
- Created: 2014-10-03T15:29:46.000Z (about 10 years ago)
- Default Branch: master
- Last Pushed: 2024-05-08T12:32:44.000Z (6 months ago)
- Last Synced: 2024-05-22T11:12:33.285Z (6 months ago)
- Language: JavaScript
- Size: 3.94 MB
- Stars: 2,850
- Watchers: 49
- Forks: 208
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: .github/CONTRIBUTING.md
- Funding: .github/FUNDING.yml
- License: LICENSE
- Codeowners: .github/CODEOWNERS
Awesome Lists containing this project
README
[![npm][npm]][npm-url]
[![node][node]][node-url]
[![tests][tests]][tests-url]
[![coverage][cover]][cover-url]
[![size][size]][size-url]
Webpack discussion: [![discussion][discussion]][discussion-url]
PostCSS chat: [![chat-postcss][chat-postcss]][chat-postcss-url]
# postcss-loader
Loader to process CSS with [`PostCSS`](https://github.com/postcss/postcss).
## Getting Started
You need webpack v5 to use the latest version. For Webpack v4, you have to install postcss-loader v4.
To begin, you'll need to install `postcss-loader` and `postcss`:
```console
npm install --save-dev postcss-loader postcss
```
or
```console
yarn add -D postcss-loader postcss
```
or
```console
pnpm add -D postcss-loader postcss
```
Then add the plugin to your `webpack` config. For example:
> In the following configuration the plugin [`postcss-preset-env`](https://github.com/csstools/postcss-preset-env) is used, which is not installed by default.
**file.js**
```js
import css from "file.css";
```
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
[
"postcss-preset-env",
{
// Options
},
],
],
},
},
},
],
},
],
},
};
```
Alternative use with [config files](#config):
**postcss.config.js**
```js
module.exports = {
plugins: [
[
"postcss-preset-env",
{
// Options
},
],
],
};
```
The loader **automatically** searches for configuration files.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: ["style-loader", "css-loader", "postcss-loader"],
},
],
},
};
```
And run `webpack` via your preferred method.
## Options
- [`execute`](#execute)
- [`postcssOptions`](#postcssOptions)
- [`sourceMap`](#sourcemap)
- [`implementation`](#implementation)
### `execute`
Type:
```ts
type execute = boolean;
```
Default: `undefined`
Enable PostCSS Parser support in `CSS-in-JS`.
If you use JS styles the [`postcss-js`](https://github.com/postcss/postcss-js) parser, add the `execute` option.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.style.js$/,
use: [
"style-loader",
{
loader: "css-loader",
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
parser: "postcss-js",
},
execute: true,
},
},
],
},
],
},
};
```
### `postcssOptions`
See the file [`./src/config.d.ts`](./src/config.d.ts).
Type:
```ts
import type { Config as PostCSSConfig } from "postcss-load-config";
import type { LoaderContext } from "webpack";
type PostCSSLoaderContext = LoaderContext;
interface PostCSSLoaderAPI {
mode: PostCSSLoaderContext["mode"];
file: PostCSSLoaderContext["resourcePath"];
webpackLoaderContext: PostCSSLoaderContext;
env: PostCSSLoaderContext["mode"];
options: PostCSSConfig;
}
export type PostCSSLoaderOptions =
| PostCSSConfig
| ((api: PostCSSLoaderAPI) => PostCSSConfig);
```
Default: `undefined`
Allows to set [`PostCSS options`](https://postcss.org/api/#processoptions) and plugins.
All `PostCSS` options are supported.
There is the special `config` option for config files. How it works and how it can be configured is described below.
We recommend do not specify `from`, `to` and `map` options, because this can lead to wrong path in source maps.
If you need source maps please use the [`sourcemap`](#sourcemap) option.
For large projects, to optimize performance of the loader, it is better to provide `postcssOptions` in loader
config and specify `config: false`. This approach removes the need to lookup and load external config files multiple
times during compilation.
#### `object`
Setup `plugins`:
**webpack.config.js** (**recommended**)
```js
const myOtherPostcssPlugin = require("postcss-my-plugin");
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
"postcss-import",
["postcss-short", { prefix: "x" }],
require.resolve("my-postcss-plugin"),
myOtherPostcssPlugin({ myOption: true }),
// Deprecated and will be removed in the next major release
{ "postcss-nested": { preserveEmpty: true } },
],
},
},
},
],
},
};
```
**webpack.config.js** (**deprecated**, will be removed in the next major release)
```js
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: {
"postcss-import": {},
"postcss-short": { prefix: "x" },
},
},
},
},
],
},
};
```
Setup `syntax`:
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
// Can be `string`
syntax: "sugarss",
// Can be `object`
syntax: require("sugarss"),
},
},
},
],
},
};
```
Setup `parser`:
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
// Can be `string`
parser: "sugarss",
// Can be `object`
parser: require("sugarss"),
// Can be `function`
parser: require("sugarss").parse,
},
},
},
],
},
};
```
Setup `stringifier`:
**webpack.config.js**
```js
const Midas = require("midas");
const midas = new Midas();
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
// Can be `string`
stringifier: "sugarss",
// Can be `object`
stringifier: require("sugarss"),
// Can be `function`
stringifier: midas.stringifier,
},
},
},
],
},
};
```
#### `function`
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.(css|sss)$/i,
loader: "postcss-loader",
options: {
postcssOptions: (loaderContext) => {
if (/\.sss$/.test(loaderContext.resourcePath)) {
return {
parser: "sugarss",
plugins: [
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
}
return {
plugins: [
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
},
},
},
],
},
};
```
#### `config`
Type:
```ts
type config = boolean | string;
```
Default: `true`
Allows to set options using config files.
Options specified in the config file are combined with options passed to the loader, the loader options overwrite options from config.
##### Config Files
The loader will search up the directory tree for configuration in the following places:
- a `postcss` property in `package.json`
- a `.postcssrc` file in JSON or YAML format
- a `.postcssrc.json`, `.postcssrc.yaml`, `.postcssrc.yml`, `.postcssrc.js`, or `.postcssrc.cjs` file
- a `postcss.config.js` or `postcss.config.cjs` CommonJS module exporting an object (**recommended**)
##### Examples of Config Files
Using `object` notation:
**postcss.config.js** (**recommend**)
```js
module.exports = {
// You can specify any options from https://postcss.org/api/#processoptions here
// parser: 'sugarss',
plugins: [
// Plugins for PostCSS
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
```
Using `function` notation:
**postcss.config.js** (**recommend**)
```js
module.exports = (api) => {
// `api.file` - path to the file
// `api.mode` - `mode` value of webpack, please read https://webpack.js.org/configuration/mode/
// `api.webpackLoaderContext` - loader context for complex use cases
// `api.env` - alias `api.mode` for compatibility with `postcss-cli`
// `api.options` - the `postcssOptions` options
if (/\.sss$/.test(api.file)) {
return {
// You can specify any options from https://postcss.org/api/#processoptions here
parser: "sugarss",
plugins: [
// Plugins for PostCSS
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
}
return {
// You can specify any options from https://postcss.org/api/#processoptions here
plugins: [
// Plugins for PostCSS
["postcss-short", { prefix: "x" }],
"postcss-preset-env",
],
};
};
```
**postcss.config.js** (**deprecated**, will be removed in the next major release)
```js
module.exports = {
// You can specify any options from https://postcss.org/api/#processoptions here
// parser: 'sugarss',
plugins: {
// Plugins for PostCSS
"postcss-short": { prefix: "x" },
"postcss-preset-env": {},
},
};
```
##### Config Cascade
You can use different `postcss.config.js` files in different directories.
Config lookup starts from `path.dirname(file)` and walks the file tree upwards until a config file is found.
```
|– components
| |– component
| | |– index.js
| | |– index.png
| | |– style.css (1)
| | |– postcss.config.js (1)
| |– component
| | |– index.js
| | |– image.png
| | |– style.css (2)
|
|– postcss.config.js (1 && 2 (recommended))
|– webpack.config.js
|
|– package.json
```
After setting up your `postcss.config.js`, add `postcss-loader` to your `webpack.config.js`.
You can use it standalone or in conjunction with `css-loader` (recommended).
Use it **before** `css-loader` and `style-loader`, but **after** other preprocessor loaders like e.g `sass|less|stylus-loader`, if you use any (since [webpack loaders evaluate right to left/bottom to top](https://webpack.js.org/concepts/loaders/#configuration)).
**webpack.config.js** (**recommended**)
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/,
use: [
"style-loader",
{
loader: "css-loader",
options: {
importLoaders: 1,
},
},
"postcss-loader",
],
},
],
},
};
```
#### `boolean`
Enables/Disables autoloading config.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
config: false,
},
},
},
],
},
};
```
#### String
Allows to specify the path to the config file.
**webpack.config.js**
```js
const path = require("path");
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
loader: "postcss-loader",
options: {
postcssOptions: {
config: path.resolve(__dirname, "custom.config.js"),
},
},
},
],
},
};
```
### `sourceMap`
Type:
```ts
type sourceMap = boolean;
```
Default: depends on the `compiler.devtool` value
By default generation of source maps depends on the [`devtool`](https://webpack.js.org/configuration/devtool/) option.
All values enable source map generation except `eval` and `false` value.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader" },
{ loader: "css-loader", options: { sourceMap: true } },
{ loader: "postcss-loader", options: { sourceMap: true } },
{ loader: "sass-loader", options: { sourceMap: true } },
],
},
],
},
};
```
Alternative setup:
**webpack.config.js**
```js
module.exports = {
devtool: "source-map",
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader" },
{ loader: "css-loader" },
{ loader: "postcss-loader" },
{ loader: "sass-loader" },
],
},
],
},
};
```
### `implementation`
Type:
```ts
type implementation = object;
```
type of `implementation` should be the same as [postcss.d.ts](https://github.com/postcss/postcss/blob/main/lib/postcss.d.ts)
Default: `postcss`
The special `implementation` option determines which implementation of PostCSS to use. Overrides the locally installed `peerDependency` version of `postcss`.
**This option is only really useful for downstream tooling authors to ease the PostCSS 7-to-8 transition.**
#### `function`
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader" },
{ loader: "css-loader" },
{
loader: "postcss-loader",
options: { implementation: require("postcss") },
},
{ loader: "sass-loader" },
],
},
],
},
};
```
#### String
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
{ loader: "style-loader" },
{ loader: "css-loader" },
{
loader: "postcss-loader",
options: { implementation: require.resolve("postcss") },
},
{ loader: "sass-loader" },
],
},
],
},
};
```
## Examples
### SugarSS
You'll need to install `sugarss`:
```console
npm install --save-dev sugarss
```
Using [`SugarSS`](https://github.com/postcss/sugarss) syntax.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.sss$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: { importLoaders: 1 },
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
parser: "sugarss",
},
},
},
],
},
],
},
};
```
### Autoprefixer
You'll need to install `autoprefixer`:
```console
npm install --save-dev autoprefixer
```
Add vendor prefixes to CSS rules using [`autoprefixer`](https://github.com/postcss/autoprefixer).
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: { importLoaders: 1 },
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
[
"autoprefixer",
{
// Options
},
],
],
},
},
},
],
},
],
},
};
```
> [!WARNING]
>
> [`postcss-preset-env`](https://github.com/csstools/postcss-preset-env) includes [`autoprefixer`](https://github.com/postcss/autoprefixer), so adding it separately is not necessary if you already use the preset. More [information](https://github.com/csstools/postcss-preset-env#autoprefixer)
### PostCSS Preset Env
You'll need to install `postcss-preset-env`:
```console
npm install --save-dev postcss-preset-env
```
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: { importLoaders: 1 },
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [
[
"postcss-preset-env",
{
// Options
},
],
],
},
},
},
],
},
],
},
};
```
### CSS Modules
What is `CSS Modules`? Please [read](https://github.com/webpack-contrib/css-loader#modules).
No additional options required on the `postcss-loader` side.
To make them work properly, either add the `css-loader`’s `importLoaders` option.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
{
loader: "css-loader",
options: {
modules: true,
importLoaders: 1,
},
},
"postcss-loader",
],
},
],
},
};
```
### CSS-in-JS and [`postcss-js`](https://github.com/postcss/postcss-js)
You'll need to install `postcss-js`:
```console
npm install --save-dev postcss-js
```
If you want to process styles written in JavaScript, use the [`postcss-js`](https://github.com/postcss/postcss-js) parser.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.style.js$/,
use: [
"style-loader",
{
loader: "css-loader",
options: {
importLoaders: 2,
},
},
{
loader: "postcss-loader",
options: {
postcssOptions: {
parser: "postcss-js",
},
execute: true,
},
},
"babel-loader",
],
},
],
},
};
```
As result you will be able to write styles in the following way
```js
import colors from "./styles/colors";
export default {
".menu": {
color: colors.main,
height: 25,
"&_link": {
color: "white",
},
},
};
```
> [!WARNING]
>
> If you are using Babel you need to do the following in order for the setup to work
> 1. Add [`babel-plugin-add-module-exports`](https://github.com/59naga/babel-plugin-add-module-exports) to your configuration.
> 2. You need to have only one **default** export per style module.
### Extract CSS
Using [`mini-css-extract-plugin`](https://github.com/webpack-contrib/mini-css-extract-plugin).
**webpack.config.js**
```js
const isProductionMode = process.env.NODE_ENV === "production";
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
module.exports = {
mode: isProductionMode ? "production" : "development",
module: {
rules: [
{
test: /\.css$/,
use: [
isProductionMode ? MiniCssExtractPlugin.loader : "style-loader",
"css-loader",
"postcss-loader",
],
},
],
},
plugins: [
new MiniCssExtractPlugin({
filename: isProductionMode ? "[name].[contenthash].css" : "[name].css",
}),
],
};
```
### Emit assets
To write a asset from PostCSS plugin to the webpack, need to add a message in `result.messages`.
The message should contain the following fields:
- `type` = `asset` - Message type (require, should be equal `asset`)
- `file` - file name (require)
- `content` - file content (require)
- `sourceMap` - sourceMap
- `info` - asset info
**webpack.config.js**
```js
const postcssCustomPlugin = (opts = {}) => {
return {
postcssPlugin: "postcss-custom-plugin",
Once: (root, { result }) => {
result.messages.push({
type: "asset",
file: "sprite.svg",
content: "...",
});
},
};
};
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [postcssCustomPlugin()],
},
},
},
],
},
],
},
};
```
### Add dependencies, contextDependencies, buildDependencies, missingDependencies
The dependencies are necessary for webpack to understand when it needs to run recompilation on the changed files.
There are two way to add dependencies:
1. (Recommended). The plugin may emit messages in `result.messages`.
The message should contain the following fields:
- `type` = `dependency` - Message type (require, should be equal `dependency`, `context-dependency`, `build-dependency` or `missing-dependency`)
- `file` - absolute file path (require)
**webpack.config.js**
```js
const path = require("path");
const postcssCustomPlugin = (opts = {}) => {
return {
postcssPlugin: "postcss-custom-plugin",
Once: (root, { result }) => {
result.messages.push({
type: "dependency",
file: path.resolve(__dirname, "path", "to", "file"),
});
},
};
};
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
plugins: [postcssCustomPlugin()],
},
},
},
],
},
],
},
};
```
Or you can use ready-made plugin [postcss-add-dependencies](https://www.npmjs.com/package/postcss-add-dependencies).
2. Pass `loaderContext` in plugin.
**webpack.config.js**
```js
const path = require("path");
module.exports = {
module: {
rules: [
{
test: /\.css$/i,
use: [
"style-loader",
"css-loader",
{
loader: "postcss-loader",
options: {
postcssOptions: {
config: path.resolve(__dirname, "path/to/postcss.config.js"),
},
},
},
],
},
],
},
};
```
**postcss.config.js**
```js
module.exports = (api) => ({
plugins: [
require("path/to/postcssCustomPlugin.js")({
loaderContext: api.webpackLoaderContext,
}),
],
});
```
**postcssCustomPlugin.js**
```js
const path = require("path");
const postcssCustomPlugin = (opts = {}) => {
return {
postcssPlugin: "postcss-custom-plugin",
Once: (root, { result }) => {
opts.loaderContext.addDependency(
path.resolve(__dirname, "path", "to", "file"),
);
},
};
};
postcssCustomPlugin.postcss = true;
module.exports = postcssCustomPlugin;
```
## Contributing
Please take a moment to read our contributing guidelines if you haven't yet done so.
[CONTRIBUTING](./.github/CONTRIBUTING.md)
## License
[MIT](./LICENSE)
[npm]: https://img.shields.io/npm/v/postcss-loader.svg
[npm-url]: https://npmjs.com/package/postcss-loader
[node]: https://img.shields.io/node/v/postcss-loader.svg
[node-url]: https://nodejs.org
[tests]: https://github.com/webpack-contrib/postcss-loader/workflows/postcss-loader/badge.svg
[tests-url]: https://github.com/webpack-contrib/postcss-loader/actions
[cover]: https://codecov.io/gh/webpack-contrib/postcss-loader/branch/master/graph/badge.svg
[cover-url]: https://codecov.io/gh/webpack-contrib/postcss-loader
[discussion]: https://img.shields.io/github/discussions/webpack/webpack
[discussion-url]: https://github.com/webpack/webpack/discussions
[chat-postcss]: https://badges.gitter.im/postcss/postcss.svg
[chat-postcss-url]: https://gitter.im/postcss/postcss
[size]: https://packagephobia.now.sh/badge?p=postcss-loader
[size-url]: https://packagephobia.now.sh/result?p=postcss-loader