webpack升级到4，webpack.config.js配置文件怎么改

Question

问题描述：
没事瞎折腾，把webpack从3.6升级到4.39.1，花了一上午时间把项目npm run dev起来，运行成功，但是样式全丢了，图片路径也不对。。

一下午配置文件改的像被狗啃了一样。。。。webpack配置读起来勉强还能读懂，自己写实在整不出来。。

先来看util.js

'use strict'
const path = require('path')
const config = require('../config')
// const ExtractTextPlugin = require('extract-text-webpack-plugin')
const MiniCssExtractPlugin = require("mini-css-extract-plugin")
const packageConfig = require('../package.json')

exports.assetsPath = function (_path) {
  const assetsSubDirectory = process.env.NODE_ENV === 'production'
    ? config.build.assetsSubDirectory
    : config.dev.assetsSubDirectory

  return path.posix.join(assetsSubDirectory, _path)
}

exports.cssLoaders = function (options) {
  options = options || {}

  const cssLoader = {
    loader: 'css-loader',
    options: {
      sourceMap: options.sourceMap
    }
  }

  const postcssLoader = {
    loader: 'postcss-loader',
    options: {
      sourceMap: options.sourceMap
    }
  }

  // generate loader string to be used with extract text plugin
  function generateLoaders (loader, loaderOptions) {
    const loaders = options.usePostCSS ? [cssLoader, postcssLoader] : [cssLoader]

    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,
      //   publicPath: '../../',
      //   fallback: 'vue-style-loader'
      // })
      return [MiniCssExtractPlugin.loader, "css-loader"].concat(loaders)
    } else {
      return ['vue-style-loader'].concat(loaders)
    }
  }

  // https://vue-loader.vuejs.org/en/configurations/extract-css.html
  return {
    css: generateLoaders(),
    postcss: generateLoaders(),
    less: generateLoaders('less'),
    sass: generateLoaders('sass', { indentedSyntax: true }),
    scss: generateLoaders('sass'),
    stylus: generateLoaders('stylus'),
    styl: generateLoaders('stylus')
  }
}

// Generate loaders for standalone style files (outside of .vue)
exports.styleLoaders = function (options) {
  const output = []
  const loaders = exports.cssLoaders(options)

  for (const extension in loaders) {
    const loader = loaders[extension]
    output.push({
      test: new RegExp('\\.' + extension + '$'),
      use: loader
    })
  }

  return output
}

exports.createNotifierCallback = () => {
  const notifier = require('node-notifier')

  return (severity, errors) => {
    if (severity !== 'error') return

    const error = errors[0]
    const filename = error.file && error.file.split('!').pop()

    notifier.notify({
      title: packageConfig.name,
      message: severity + ': ' + error.name,
      subtitle: filename || '',
      icon: path.join(__dirname, 'logo.png')
    })
  }
}

webpack.base.conf.js

'use strict'
const path = require('path')
const utils = require('./utils')
const config = require('../config')
const vueLoaderConfig = require('./vue-loader.conf')
// const MiniCssExtractPlugin = require("mini-css-extract-plugin")

function resolve (dir) {
  return path.join(__dirname, '..', dir)
}

const createLintingRule = () => ({
  test: /\.(js|vue)$/,
  loader: 'eslint-loader',
  enforce: 'pre',
  include: [resolve('src'), resolve('test')],
  options: {
    formatter: require('eslint-friendly-formatter'),
    emitWarning: !config.dev.showEslintErrorsInOverlay
  }
})

module.exports = {
  context: path.resolve(__dirname, '../'),
  entry: {
    app: './src/main.js'
  },
  output: {
    path: config.build.assetsRoot,
    filename: '[name].js',
    publicPath: process.env.NODE_ENV === 'production'
      ? config.build.assetsPublicPath
      : config.dev.assetsPublicPath
  },
  externals: {
    "AMap":"AMap"
  },
  resolve: {
    extensions: ['.js', '.vue', '.json'],
    alias: {
      'vue$': 'vue/dist/vue.esm.js',
      '@': resolve('src'),
    }
  },
  module: {
    rules: [
      ...(config.dev.useEslint ? [createLintingRule()] : []),
      {
        test: /\.vue$/,
        loader: 'vue-loader',
        options: vueLoaderConfig
      },
      {
        test: /\.js$/,
        loader: 'babel-loader',
        include: [resolve('src'), resolve('test'), resolve('node_modules/webpack-dev-server/client')]
      },
      {
        test: /\.sass$/,
        loaders: ['style', 'css', 'sass']
      },
      {
        test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('img/[name].[hash:7].[ext]')
        }
      },
      {
        test: /\.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('media/[name].[hash:7].[ext]')
        }
      },
      // {
      //   test: /\.(scss|sass|css)$/i,
      //   use: [MiniCssExtractPlugin.loader, "css-loader"],
      // },
      {
        test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('fonts/[name].[hash:7].[ext]')
        }
      }
    ]
  },
  node: {
    // prevent webpack from injecting useless setImmediate polyfill because Vue
    // source contains it (although only uses it if it's native).
    setImmediate: false,
    // prevent webpack from injecting mocks to Node native modules
    // that does not make sense for the client
    dgram: 'empty',
    fs: 'empty',
    net: 'empty',
    tls: 'empty',
    child_process: 'empty'
  }
}

webpack.dev.conf.js

'use strict'
process.traceDeprecation = true
const utils = require('./utils')
const webpack = require('webpack')
const config = require('../config')
const merge = require('webpack-merge')
const path = require('path')
const baseWebpackConfig = require('./webpack.base.conf')
const CopyWebpackPlugin = require('copy-webpack-plugin')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')
const portfinder = require('portfinder')
const { VueLoaderPlugin } = require('vue-loader');
// const VueLoaderPlugin = require('vue-loader/lib/plugin')
// const VueLoaderPlugin = require('vue-loader')
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const HOST = process.env.HOST
const PORT = process.env.PORT && Number(process.env.PORT)

const devWebpackConfig = merge(baseWebpackConfig, {
  mode: 'development',
  module: {
    // rules: utils.styleLoaders({ sourceMap: config.dev.cssSourceMap, usePostCSS: true })
    rules: utils.styleLoaders({ sourceMap: true, usePostCSS: true, extract: false})
  },
  // cheap-module-eval-source-map is faster for development
  devtool: config.dev.devtool,

  // these devServer options should be customized in /config/index.js
  devServer: {
    clientLogLevel: 'warning',
    historyApiFallback: {
      rewrites: [
        { from: /.*/, to: path.posix.join(config.dev.assetsPublicPath, 'index.html') },
      ],
    },
    hot: true,
    contentBase: false, // since we use CopyWebpackPlugin.
    compress: true,
    host: HOST || config.dev.host,
    port: PORT || config.dev.port,
    open: config.dev.autoOpenBrowser,
    overlay: config.dev.errorOverlay
      ? { warnings: false, errors: true }
      : false,
    publicPath: config.dev.assetsPublicPath,
    proxy: config.dev.proxyTable,
    quiet: true, // necessary for FriendlyErrorsPlugin
    watchOptions: {
      poll: config.dev.poll,
    }
  },
  optimization: {
    namedModules: true
  },
  plugins: [
    new VueLoaderPlugin(),
    new MiniCssExtractPlugin({
      filename: '[name].css',
      chunkFilename: "[id].css"
    }),
    // new MiniCssExtractPlugin({
    //   attributes: {
    //     id: 'target',
    //     'data-target': 'example',
    //   },
    // }),
    new webpack.DefinePlugin({
      'process.env': require('../config/dev.env')
    }),
    new webpack.HotModuleReplacementPlugin(),
    // new webpack.NamedModulesPlugin(), // HMR shows correct file names in console on update.
    // new webpack.NoEmitOnErrorsPlugin(),
    // https://github.com/ampedandwired/html-webpack-plugin
    new HtmlWebpackPlugin({
      filename: 'index.html',
      template: 'index.html',
      inject: true
    }),
    // copy custom static assets
    new CopyWebpackPlugin({
      // {
      //   from: path.resolve(__dirname, '../static'),
      //   to: config.dev.assetsSubDirectory,
      //   ignore: ['.*']
      // }
      patterns: [
        { 
          from: path.join(__dirname,'../static'),
          to: config.dev.assetsSubDirectory,
        }        
      ],
      options:{

      }
    })
  ]
})

module.exports = new Promise((resolve, reject) => {
  portfinder.basePort = process.env.PORT || config.dev.port
  portfinder.getPort((err, port) => {
    if (err) {
      reject(err)
    } else {
      // publish the new Port, necessary for e2e tests
      process.env.PORT = port
      // add port to devServer config
      devWebpackConfig.devServer.port = port

      // Add FriendlyErrorsPlugin
      devWebpackConfig.plugins.push(new FriendlyErrorsPlugin({
        compilationSuccessInfo: {
          messages: [`Your application is running here: http://${devWebpackConfig.devServer.host}:${port}`],
        },
        onErrors: config.dev.notifyOnErrors
        ? utils.createNotifierCallback()
        : undefined
      }))

      resolve(devWebpackConfig)
    }
  })
})

===========
15:37更新

真是卧了个大槽
你们猜怎么着，我把util.js中的

return ['vue-style-loader'].concat(loaders)

改成了

return ['style-loader'].concat(loaders)

样式就有了!!!!浪费了我一下午时间！！！！
这是咋肥四？？？？
忍不住口吐芬芳。。。

Answer 1

1. 建议直接升级到 webpack 5。
2. 建议直接从头配，基本上照着文档，配个项目也就个把小时。