Pcss-loader NPM

pcss-loader

A loader for Webpack that imports pcss files and return js modules.

How to setup in your webpack configuration

Install with npm i -D pcss-loader. Then your webpack configuration must contain the following module:

...
module: {
    rules: [
    ...
        {
            // You can use antoher extension
            test: /\.pcss$/i,
            // You can also exclude, but inclusion is
            // more specific and more predictable
            include: 'your_src_folder_path',
            use: {
                loader: 'pcss-loader',
                // Not mandatory
                options: {}
            }
        }
    ]
},
...

Default options

options: {
    // Set to true to minify the output, important for production
    minified: false,
    // Default values for the env
    presetEnv: {
        stage: 0,
        features: ['css-nesting'],
        browsers: 'cover 100%'
    },
    // Array of additionnal plugins
    // you can add any post-css plugin
    customPlugins: []
}

You can read the documentation about postcss-preset-env to learn more about the options you can pass to presetEnv.

Plugins in use

You can add any plugins you want to post-css with the customPlugins array. But here are the ones currently in use.

postcss-nested: to use nested css.
postcss-preset-env: to pass a target environment for the transpilation.
postcss-import: to allow @ imports like @import 'src/UiAssets/Colors.pcss';.
postcss-simple-vars: to use scss like $ vars.
cssnano: to minify the output. Only used if your pass the minified option to true.

Input and output

If you have the two following pcss files:

/* Colors.pcss */
$mainColor: #00c;

/* Styles.pcss */
@import 'src_path/Colors.pcss';

body {
  color: #000;
}

.__SCOPE {
  color: #c00;

  > .example {
    color: $mainColor;
  }
}

And you import them in a JavaScript file with import AppStyles from './AppStyles.pcss';, you obtain this object:

{
    hash: "_d9ce6323d17badc0ff20482741b70d84",
    styles: `
        body {
            color: #000;
        }

        ._d9ce6323d17badc0ff20482741b70d84 {
            color: #c00;
        }

        ._d9ce6323d17badc0ff20482741b70d84 > .example {
            color: #00c;
        }
    `,
}

It should be injected in a style tag in your DOM.

The value of styles will be minified if you pass minified: true in the options and will be: body{color:#000}._8fd83ea9dc8f28944de69aac4284bba3{color:#c00}._8fd83ea9dc8f28944de69aac4284bba3>.example{color:#00c}

The `.__SCOPE` class

The loader uses that class to scope your styles. Then you can use the hash returned by the loader as a class for the container and so the styles will be scoped only to his children.

You can also store the hash to make sure that you don't inject twice the same styles.