parcel-bundler/src/transforms/postcss.js

<p align="center"> <a href="https://parceljs.org/" target="_blank"> <img alt="Parcel" src="https://user-images.githubusercontent.com/19409/31321658-f6aed0f2-ac3d-11e7-8100-1587e676e0ec.png" width="749"> </a> </p>

const localRequire = require('../utils/localRequire');
const loadPlugins = require('../utils/loadPlugins');
const postcss = require('postcss');
const Config = require('../utils/config');
const cssnano = require('cssnano');

module.exports = async function(asset) {
  let config = await getConfig(asset);
  if (!config) {
    return;
  }

  await asset.parseIfNeeded();
  let res = await postcss(config.plugins).process(asset.getCSSAst(), config);

  asset.ast.css = res.css;
  asset.ast.dirty = false;
};

async function getConfig(asset) {
  let config =
    asset.package.postcss ||
    (await Config.load(asset.name, [
      '.postcssrc',
      '.postcssrc.js',
      'postcss.config.js'
    ]));
  if (!config && !asset.options.minify) {
    return;
  }

  config = config || {};

  let postcssModulesConfig = {
    getJSON: (filename, json) => (asset.cssModules = json)
  };

  if (config.plugins && config.plugins['postcss-modules']) {
    postcssModulesConfig = Object.assign(
      config.plugins['postcss-modules'],
      postcssModulesConfig
    );
    delete config.plugins['postcss-modules'];
  }

  config.plugins = await loadPlugins(config.plugins, asset.name);

  if (config.modules) {
    let postcssModules = await localRequire('postcss-modules', asset.name);
    config.plugins.push(postcssModules(postcssModulesConfig));
  }

  if (asset.options.minify) {
    config.plugins.push(cssnano());
  }

  config.from = asset.name;
  config.to = asset.name;
  return config;
}