webpack3升级为webpack4的实践

这次webpack升级提升了不少构建速度：生产打包提升了30%；开发构建提升40%，开发热更新提升70%

之前尝试过一些在webpack3的基础上做的构建优化，例如引入HappyPack优化构建速度，开启loader缓存和优化包查找路径等等，详情可以查看前端webpack构建优化

但是随着时间的推移，这种优化产生的效果越来越弱化，手上的项目体积越来越大，对本地开发热更新速度和生产打包发布速度都有了很大的影响。

webpack3升级到webpack4迫在眉睫，这篇博文将记录一些我在升级过程中遇到的坑。

当你遇到这些坑时，通过搜索引擎找到我这篇文章，如果能够解决了手上的webpack配置问题，然后发自内心的感到 ”Save my day！“，”It helps me！“，”Solved my problem！“，”Works for me！“ ，我会感觉自己的这篇博文很有意义。

升级到 webpack 4
移除 CommonsChunkPlugin，默认使用 SplitChunksPlugin 分割代码
升级 html-webpack-plugin
移除 extract-text-webpack-plugin，引入 mini-css-extract-plugin 并配置 css-loader
配置 mode 属性
升级 vue-loader 到 v14.2.2
更新 HtmlWebpackPlugin 的 chunkSortMode
修复大小限制的报错
重命名 app.js，生成 vendors.js
mini-css-extract-plugin 的配置放在 webpack.base.conf.js
调试开发环境可用
引入analyzer分析分析包大小
webpack3与webpack4打包对比
文件可以更小一些吗？构建速度可以更快一些吗？
升级vue-loader到v15并且替换happyPack为thread-loader
webpack3与webpack4开发依赖对比
总结

升级 webpack 到 4

"webpack": "^3.6.0" -> "webpack": "^4.43.0"

yarn add -D webpack@4.43.0

移除 CommonsChunkPlugin

plugins: [
  // // split vendor js into its own file
  // new webpack.optimize.CommonsChunkPlugin({
  //   name: 'vendor',
  // }),
  // // extract webpack runtime and module manifest to its own file in order to
  // // prevent vendor hash from being updated whenever app bundle is updated
  // new webpack.optimize.CommonsChunkPlugin({
  //   name: 'manifest',
  //   minChunks: Infinity,
  // }),
  // // This instance extracts shared chunks from code splitted chunks and bundles them
  // // in a separate chunk, similar to the vendor chunk
  // // see: https://webpack.js.org/plugins/commons-chunk-plugin/#extra-async-commons-chunk
  // new webpack.optimize.CommonsChunkPlugin({
  //   name: 'app',
  //   async: 'vendor-async',
  //   children: true,
  //   minChunks: 3,
  // }),
];

升级 html-webpack-plugin

"html-webpack-plugin": "^2.30.1" -> "html-webpack-plugin": "^4.3.0"

// https://stackoverflow.com/questions/49942558/deprecationwarning-tapable-plugin-is-deprecated-use-new-api-on-hooks-instea
// error
Tapable.apply is deprecated. Call apply on the plugin directly instead

yarn add -D html-webpack-plugin@latest

移除 extract-text-webpack-plugin，引入 mini-css-extract-plugin 并配置 css-loader

// const ExtractTextPlugin = require('extract-text-webpack-plugin');
// plugins:[
// extract css into its own file
// new ExtractTextPlugin({
//   filename: utils.assetsPath('css/[name].[contenthash].css'),
//   // Setting the following option to `false` will not extract CSS from codesplit chunks.
//   // Their CSS will instead be inserted dynamically with style-loader when the codesplit chunk has been loaded by
//   // webpack. It's currently set to `true` because we are seeing that sourcemaps are included in the codesplit
//   // bundle as well when it's `false`, increasing file size: https://github.com/vuejs-templates/webpack/issues/1110
//   allChunks: true,
// }),
// ]

// extract: true
// if (options.extract) {
//   return ExtractTextPlugin.extract({
//     use: loaders,
//     fallback: 'vue-style-loader',
//   });
// }

yarn add -D mini-css-extract-plugin

// webpack.prod.conf.js
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
plugins: [
    new MiniCssExtractPlugin(filename: utils.assetsPath('css/[name].[contenthash].css'))
];

// webpack.base.conf.js
module.exports = {
  module: {
    rules: [
      {
        test: /\.(sa|sc|c)ss$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              hmr: process.env.NODE_ENV === "development",
            },
          },
          "css-loader",
          "postcss-loader",
          "sass-loader",
        ],
      },
    ],
  },
};

配置 mode 属性

The 'mode' option has not been set, webpack will fallback to 'production' for this value. Set 'mode' option to 'development' or 'production' to enable defaults for each environment.

mode: "production";

升级 vue-loader

"vue-loader": "^13.3.0" -> "vue-loader": "14.2.2"

TypeError: Cannot read property 'vueOptions' of undefined

yarn add -D vue-loader@latest

vue-loader was used without the corresponding plugin. Make sure to include VueLoaderPlugin in your webpack config

// https://github.com/symfony/webpack-encore/issues/311
You probably use vue-loader v15 which was released yesterday and introduces a lot of changes compared to v14. One of these changes is that you have to use an extra plugin: VueLoaderPlugin (that's not handled yet by Encore).

In the meantime could you try removing your version of the vue-loader/VueLoaderPlugin and adding vue-loader@^14.2.2 instead?

yarn add -D vue-loader@14.2.2

(1:1) Unknown word

> 1 | // extracted by mini-css-extract-plugin

移除 postcss-loader。

// postcss: generateLoaders()

更新 HtmlWebpackPlugin 的 chunkSortMode

// https://www.cnblogs.com/wyliunan/p/10238717.html
Unhandled rejection Error: "dependency" is not a valid chunk sort mode

设置为 HtmlWebpackPlugin 的 chunkSortMode 为"auto": https://github.com/jantimon/h...

修复大小限制的报错

AssetsOverSizeLimitWarning: asset size limit: The following asset(s) exceed the recommended size limit (244 KiB 250000Byte).
This can impact web performance.

// webpack.config.js
module.exports = {
  performance: {
    hints: "warning",
    maxEntrypointSize: 5000 * 1024,
    maxAssetSize: 5000 * 1024,
  },
};

生成 manifest.js，生成 vendors.js

// https://webpack.js.org/configuration/optimization/#optimizationsplitchunks
// 生成manifest.js
optimization: {
    runtimeChunk: {
        name:'manifest'
    }
},

// https://webpack.js.org/plugins/split-chunks-plugin/#split-chunks-example-1
// 生成 vendors.js
optimization: {
  splitChunks: {
    cacheGroups: {
      commons: {
        test: /[\\/]node_modules[\\/]/,
        name: 'vendors',
        chunks: 'all',
      },
    },
  },
}

  output: {
-   chunkFilename: utils.assetsPath('js/[id].[chunkhash].js'),
+   chunkFilename: utils.assetsPath('js/[name].[chunkhash].js'),
  },

调试开发环境可用

Error: Cannot find module 'webpack/bin/config-yargs'

https://github.com/mzgoddard/jest-webpack/issues/27

"webpack-cli": "^2.1.3",
"webpack-dev-server": "^3.1.4"

mode: 'development',

// webpack Error: Callback was already called.
// https://github.com/webpack-contrib/mini-css-extract-plugin/issues/493
// webpack.dev.js
plugins:[
    new MiniCssExtractPlugin(),
]

// https://segmentfault.com/q/1010000012054980
// BaseClient.js:12 Uncaught TypeError: Cannot assign to read only property 'exports' of object '#<Object>'

安装transform-es2015-modules-commonjs并且在.babelrc中配置。

yarn add -D transform-es2015-modules-commonjs

// .babelrc
"plugins": [
    "transform-es2015-modules-commonjs"
]

引入analyzer分析分析包大小

// package.json
scripts:{
  "build:analyse": "NODE_ENV=production source_map=false npm_config_report=true node build/build.js"
}

// webpack.prod.conf.js
if (config.build.bundleAnalyzerReport) {
  const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin;
  webpackConfig.plugins.push(new BundleAnalyzerPlugin());
}

webpack3与webpack4打包对比

版本	文件大小(Parsed)	文件大小(Gzipped)	chunk数	生产构建时间	开发构建时间	开发热更新体感
webpack3.6.0	6.09MB	1.76MB	73	52196ms	70103ms	慢(12079ms)
webpack4.43.0	7.07MB	1.98MB	88	40727ms	45448ms	快(3394ms)

机器参数：
MacBook Pro (15-inch, 2019)
处理器 2.3 GHz Intel Core i9
内存 16 GB 2400 MHz DDR4

文件可以更小一些吗？构建速度可以更快一些吗？

未使用TerserPlugin而是用UglifyjsPlugin
OptimizeCSSPlugin位置放错
如果手动配置splitChunks的话，一定要把没有配置的参数也配置上
devtool由最慢的“source-map”改为false

引入TerserPlugin的话，需要首先升级node到v10.17.0+。

sudo n v10.17.0

const TerserPlugin = require('terser-webpack-plugin');
module.exports = {
  optimization: {
    minimize: true,
    minimizer: [
      // Compress extracted CSS. We are using this plugin so that possible
      // duplicated CSS from different presentation can be deduped.
      new OptimizeCSSPlugin({
        cssProcessorOptions: config.build.productionSourceMap ? { safe: true, map: { inline: false } } : { safe: true },
      }),
      new TerserPlugin({
        cache: true,
        parallel: true,
        sourceMap: Boolean(config.build.productionSourceMap),
      }),
    ],
  }
}

增加下面的配置：

optimization: {
  splitChunks: {
    chunks: 'async',
    minSize: 30000,
    maxSize: 0,
    minChunks: 1,
    maxAsyncRequests: 5,
    maxInitialRequests: 3,
    automaticNameDelimiter: '~',
    automaticNameMaxLength: 30,
  }
}

现在的webpack3和webpack4打包分析:

版本	文件大小(Parsed)	文件大小(Gzipped)	chunk数	生产构建时间	开发构建时间	开发热更新体感
webpack3.6.0	6.09MB	1.76MB	73	52196ms	70103ms	慢(12079ms)
webpack4.43.0(优化前)	7.07MB	1.98MB	88	40727ms	45448ms	快(3394ms)
webpack4.43.0(优化后)	7.02MB	1.98MB	88	34585ms	45448ms	快(3394ms)

通过对比发现，提升了大概5秒的打包速度。

升级vue-loader到v15并且引入thread-loader加速vue-loader

warning No parser and no filepath given, using 'babel' the parser now but this will throw an error in the future. Please specify a parser or a filepath so one can be inferred

为什么引入thread-loader加速vue-loader？
因为HappyPack无法加速vue-loader15。
https://github.com/vuejs/vue-...

yyx990803:vue-loader 15 does not support HappyPack. Use thread-loader instead.

顺便升级eslint-loader到4。
"eslint-loader": "^1.7.1"->"eslint-loader": "^4.0.2"

  // plugins: [
  //   new HappyPack({
  //     id: 'happy-eslint-loader',
  //     threadPool: happyThreadPool,
  //     loaders: ['eslint-loader?cacheDirectory=true'],
  //   }),
  //   new HappyPack({
  //     id: 'happy-vue-loader',
  //     threadPool: happyThreadPool,
  //     loaders: ['vue-loader?cacheDirectory=true'],
  //   }),
  //   new HappyPack({
  //     id: 'happy-babel-loader',
  //     threadPool: happyThreadPool,
  //     loaders: ['babel-loader?cacheDirectory=true'],
  //   }),
  // ]

rules: [
  {
    test: /\.(js|vue)$/,
    use: [
      { loader: 'thread-loader' },
      {
        loader: 'eslint-loader',
        options: {
          formatter: require('eslint-friendly-formatter'),
          emitWarning: !config.dev.showEslintErrorsInOverlay,
        },
      },
    ],
    enforce: 'pre',
    include: [resolve('src'), resolve('test')],
  },
  {
    test: /\.vue$/,
    use: ['thread-loader', 'vue-loader'],
    exclude: (file) => /node_modules/.test(file) && !/\.vue\.js/.test(file),
  },
  {
    test: /\.js$/,
    use: ['thread-loader', 'babel-loader'],
    include: [resolve('src'), resolve('test'), resolve('node_modules/webpack-dev-server/client')],
  },
  {
    test: /\.(sa|sc|c)ss$/,
    use: [
      {
        loader: process.env.NODE_ENV === 'development' ? 'vue-style-loader' : MiniCssExtractPlugin.loader,
        options: {
          hmr: process.env.NODE_ENV === 'development',
        },
      },
      'css-loader',
      'postcss-loader',
      'sass-loader',
    ],
  },
]

error:despite it was not able to fulfill desired ordering with these modules:

new MiniCssExtractPlugin({
  ignoreOrder: true,
}),

现在的webpack3和webpack4打包分析:

版本	文件大小(Parsed)	文件大小(Gzipped)	chunk数	生产构建时间	开发构建时间	开发热更新体感
webpack3.6.0	6.09MB	1.76MB	73	52196ms	70103ms	慢(12079ms)
webpack4.43.0(优化前)	7.07MB	1.98MB	88	40727ms	45448ms	快(3394ms)
webpack4.43.0(第一次优化)	7.02MB	1.98MB	88	34585ms	45448ms	快(3394ms)
webpack4.43.0(第二次优化)	6.7MB	1.91MB	88	34585ms	41657ms	快(3394ms)

webpack3与webpack4开发依赖对比

// webpack3
"webpack": "^3.6.0"
"webpack-dev-server": "^2.9.1"
"eslint-loader": "^1.7.1"
"vue-loader": "^13.3.0"
"happypack": "^5.0.0"
"html-webpack-plugin": "^2.30.1"
"extract-text-webpack-plugin": "^3.0.0"
"uglifyjs-webpack-plugin": "^1.1.1"

// webpack4
"webpack": "^4.43.0"
"webpack-cli": "^3.3.11"
"webpack-dev-server": "^3.7.2"
"thread-loader": "^2.1.3"
"eslint-loader": "^4.0.2"
"vue-loader": "^15.9.2"
"html-webpack-plugin": "^4.3.0"
"mini-css-extract-plugin": "^0.9.0"
"terser-webpack-plugin": "^3.0.1"
"babel-plugin-transform-es2015-modules-commonjs": "^6.26.2"

总结

webpack3到webpack4的升级，主要做了以下这些事情

升级依赖：升级webpack major version为webpack4，升级vue-loader，升级html-webpack-plugin等等
代码分割：移除了CommonsChunkPlugin；引入SplitChunksPlugin，设置mode属性为production，optimization拆分出webpack3中的manifest和vendors
压缩css：移除extract-text-webpack-plugin；引入mini-css-extract-plugin，使用mini-css-extract-plugin的loader重新配置sass-loader,postcss-loader和css-loader，它会为每个包含css的js文件单独构建一个js文件
代码热更新：升级webpack-cli和webpack-dev-server，并且设置mode为development

反思

执行力是第一生产力
这次webpack升级提升了不少构建速度：生产打包提升了30%；开发构建提升40%，开发热更新提升70%
这次webpack升级没有减小包大小，有尝试使用tree shaking，但是没有成功，有待在tree shaking上继续做实践

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