AMR/node_modules/vue-loader/lib/parser.js

const compiler = require('vue-template-compiler')
const cache = require('lru-cache')(100)
const hash = require('hash-sum')
const SourceMapGenerator = require('source-map').SourceMapGenerator

const splitRE = /\r?\n/g
const emptyRE = /^(?:\/\/)?\s*$/

module.exports = (content, filename, needMap, sourceRoot, needCSSMap) => {
  const cacheKey = hash((filename + content).replace(/\\/g, '/'))
  let output = cache.get(cacheKey)
  if (output) return output
  output = compiler.parseComponent(content, { pad: 'line' })
  if (needMap) {
    if (output.script && !output.script.src) {
      output.script.map = generateSourceMap(
        filename,
        content,
        output.script.content,
        sourceRoot
      )
    }
    if (needCSSMap && output.styles) {
      output.styles.forEach(style => {
        if (!style.src) {
          style.map = generateSourceMap(
            filename,
            content,
            style.content,
            sourceRoot
          )
        }
      })
    }
  }
  cache.set(cacheKey, output)
  return output
}

function generateSourceMap (filename, source, generated, sourceRoot) {
  const map = new SourceMapGenerator({ sourceRoot })
  map.setSourceContent(filename, source)
  generated.split(splitRE).forEach((line, index) => {
    if (!emptyRE.test(line)) {
      map.addMapping({
        source: filename,
        original: {
          line: index + 1,
          column: 0
        },
        generated: {
          line: index + 1,
          column: 0
        }
      })
    }
  })
  return map.toJSON()
}