build the mpvue project according to http://mpvue.com/mpvue/-sharp_3. The error is as follows:

function generateLoaders (loader, loaderOptions) in unitls.js {

// var ExtractTextPlugin = require("extract-text-webpack-plugin")
var MiniCssExtractPlugin = require("mini-css-extract-plugin")
function generateLoaders (loader, loaderOptions) {
    var loaders = [cssLoader, px2rpxLoader, postcssLoader]
    if (loader) {
      loaders.push({
        loader: loader + "-loader",
        options: Object.assign({}, loaderOptions, {
          sourceMap: options.sourceMap
        })
      })
    }

    // Extract CSS when that option is specified
    // (which is the case during production build)
    if (options.extract) {
      // return ExtractTextPlugin.extract({
      //   use: loaders,
      //   fallback: "vue-style-loader"
      // })
      return [
        MiniCssExtractPlugin.loader,
        {
          loader: "css-loader",
          options: {
            minimize: process.env.NODE_ENV === "production"
          }
        }
      ]
    } else {
      return ["vue-style-loader"].concat(loaders)
    }

  }

the modules that ps: depends on have been upgraded to the latest version. Trying to change ompiler.plugin to compiler.hooks.emit.tap, in dev-sever.js does not solve the problem