postcss-pipeline-webpack-plugin

A webpack plugin to process generated assets with PostCSS pipeline.

Preface

Webpack loaders are pretty cool but limited to process and generate only one file at a time. If you are extracting critical CSS or media queries into separate files, you are no longer able to process these files. This plugin was made to solve this problem.

Install

npm install --save postcss-pipeline-webpack-plugin

It requires webpack v4 to work. Please, use previous major version if you use webpack v3.

Usage

const PostCssPipelineWebpackPlugin = require('postcss-pipeline-webpack-plugin');

const pipelinePlugin = new PostCssPipelineWebpackPlugin({
  // provide an optional function to filter out unwanted CSS 
  predicate: name => /foobar.css$/.test(name),
  // provide an optional string which will be using as a suffix for newly generated files
  suffix: 'processed',
  // provide any PostCSS plugins here
  pipeline: [],
  // you can pass any relevant SourceMap options
  // see https://github.com/postcss/postcss/blob/master/docs/source-maps.md
  map: {}
});

So, you can use this initialized instance of the plugin in webpack configuration later.

module.exports = {
  mode: 'production',

  entry: './src/index.css',

  output: {
    path: path.resolve('./dest/'),
    filename: '[name].js'
  },

  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader'
        ]
      }
    ]
  },

  plugins: [
    new MiniCssExtractPlugin({
      filename: 'styles.css'
    }),
    pipelinePlugin    
  ]
};

Advanced techniques

For example, you may want to process your styles with postcss-critical-css plugin. It generates an additional file, which contains only styles between start- and stop-tags. You can’t use the optimization of generated styles before the plugin because minification removes all comments. So, you have to minify “all” and “critical” parts separately.

It’s pretty easy with postcss-pipeline-webpack-plugin. You can provide as many PostCSS pipelines as you need.

For your task, we need to set up two pipelines with one plugin in each other:

postcss-critical-split
postcss-csso

const PostCssPipelineWebpackPlugin = require('postcss-pipeline-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const criticalSplit = require('postcss-critical-split');
const csso = require('postcss-csso');

module.exports = {
  // ...  
  plugins: [
    new MiniCssExtractPlugin({
      filename: 'styles.css'
    }),
    new PostCssPipelineWebpackPlugin({
      suffix: 'critical',
      pipeline: [
        criticalSplit({
          output: criticalSplit.output_types.CRITICAL_CSS
        })
      ]
    }),
    new PostCssPipelineWebpackPlugin({
      suffix: 'min',
      pipeline: [
        csso({
          restructure: false
        })
      ],
      map: {
        inline: false
      }
    })
  ]
};

Webpack extracts all CSS into:

styles.css

PostCSS generates critical CSS into styles.critical.css. So, you get two files:

styles.css
styles.critical.css

PostCSS optimize both files with csso and create relevant SourceMaps for them:

styles.css
styles.critical.css
styles.min.css
styles.min.css.map
styles.critical.min.css
styles.critical.min.css.map

As you can see, webpack generates artifacts in one pass.

See full webpack.config.js for more details.

Change log

4.0.0

2018-03-27

[major] added webpack 4 support

3.1.0

2018-02-05

[major] made the plugin compatible with filename’s template like [name].css?[contenthash]

3.0.1

2017-08-14

[minor] upgraded webpack-sources module

3.0.0

2017-05-30

[breaking] set minimal required node.js version to 4.7
[breaking] upgraded PostCSS and other minor dependencies

2.0.0

2017-03-20

[breaking] switched to webpack 2 and upgraded minor dependencies

1.2.0

2016-12-28

[fix] added previously generated Source Maps

1.1.0

2016-12-27

[feature] suffix can contain any falsy value to skip rename
[fix] added module.exports to main file

1.0.0

2016-12-20

initial release

License

ISC

wdeer / postcss-pipeline-webpack-plugin