postcss.config.js

var path = require('path')
var postcssImport = require('postcss-import')
var cssnano = require('cssnano')
module.exports = ctx => ({
  plugins: {
    'postcss-import': {
      resolve (id, basedir) {
        if (/^~/.test(id)) return path.resolve('./node_modules', id.replace('~', ''))
        return path.resolve(basedir, id)
      }
    },
    'cssnano': ctx.env === 'production'
  }
})