Postcss-pipeline-webpack-plugin NPM

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

Compatibility

It requires webpack 5.x to work.

For webpack 4.x use postcss-pipeline-webpack-plugin@5 package.

For webpack 3.x use postcss-pipeline-webpack-plugin@3 package.

The plugin is compatible with PostCSS 6.x, 7.x and 8.x branches.

Usage

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

const pipelinePlugin = new PostCssPipelineWebpackPlugin({
  processor: postcss([
      // provide any PostCSS plugins here
  ]),
  // provide an optional function to filter out unwanted CSS
  predicate: name => /foobar.css$/.test(name),
  // provide an optional string attached to the beginning of a new file
  prefix: 'critical',
  // provide an optional string which will be using as a suffix for newly generated files
  suffix: 'processed',
  // or you can generate the name by yourself
  transformName: name => 'critical-' + name,
  // 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 the 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 postcss = require('postcss');
const criticalSplit = require('postcss-critical-split');
const csso = require('postcss-csso');

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

1) Webpack extracts all CSS into:

styles.css

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

styles.css
styles.critical.css

3) 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

6.0.0

2020-12-24

breaking made the plugin fully compatible with webpack v5

5.1.2

2019-08-02

minor updated dependencies

5.1.1

2019-07-07

minor updated version of the engines

5.1.0

2019-07-03

major added transformName option to generate destination filenames

5.0.0

2019-03-09

breaking pipeline option was replaced with processor to let the developer decide which version of the PostCSS to use
minor improved examples and documentation