stylePostLoader.js

const qs = require('querystring')
const { compileStyle } = require('@vue/component-compiler-utils')

// This is a post loader that handles scoped CSS transforms.
// Injected right before css-loader by the global pitcher (../pitch.js)
// for any <style scoped> selection requests initiated from within vue files.
module.exports = function (source, inMap) {
  const query = qs.parse(this.resourceQuery.slice(1))
  const { code, map, errors } = compileStyle({
    source,
    filename: this.resourcePath,
    id: `data-v-${query.id}`,
    map: inMap,
    scoped: !!query.scoped,
    trim: true
  })

  if (errors.length) {
    this.callback(errors[0])
  } else {
    this.callback(null, code, map)
  }
}