index.js

const postcss = require('postcss')
const cssnext = require('postcss-preset-env')
const imports = require('postcss-import')
const xtend = require('xtend')

module.exports = transform

function transform (filename, source, options, done) {
 options = xtend(options || {})
 const sourcemap = options.sourcemap
 delete options.sourcemap

 const processor = postcss([
 imports(),
 cssnext(options)
 ])

 const poptions = xtend({
 map: sourcemap === false ? false : { inline: true },
 from: filename,
 messages: {
 browser: true,
 console: false
 }
 }, options || {})

 processor.process(source, poptions).then(function (result) {
 // Collect imported files for watchify
 const files = [filename]
 result.messages.forEach(function (msg) {
 if (msg.type === 'dependency') {
 files.push(msg.file)
 }
 })

 done(null, {
 css: result.css,
 files: files
 })
 }, function (err) {
 done(err)
 })
}