记一次webpack3升级webpack4的踩坑

webpack4版本也出了很久了之前弄过一段时间的升级后面因为种种原因搁浅了今天有硬着头皮升级了一波 yeah 还好升级成功了

先贴一波原先webpack3的github配置

ps（我只是一个菜鸡= = webpack的配置很辣鸡）废话少说开撸

1 webpack升级到4.0版本并且安装webpack-cli

yarn add webpack-cli global
yarn add webpack-cli -D

　　如果不对webpack-cli进行安装的话会报错如下：

The CLI moved into a separate package:webpack-cli.
Please install 'webpack-cli' in addition to webpack itself to use the CLI.
->when using npm: npm install webpack-cli -D
->when using yarn: yarn add webpack-cli -D

2 对一些包的相关依赖

　　继续yarn run dev yeah!!! 报错了

Error: Cannot find module 'webpack/bin/config-yargs'
    at Function.Module._resolveFilename (module.js:538:15)
    at Function.Module._load (module.js:468:25)
    at Module.require (module.js:587:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\webpack-dev-server\bin\webpack-dev-server.js:54:1)
    at Module._compile (module.js:643:30)
    at Object.Module._extensions..js (module.js:654:10)
    at Module.load (module.js:556:32)
    at tryModuleLoad (module.js:499:12)
    at Function.Module._load (module.js:491:3)
error Command failed with exit code 1.

解决办法：这个就是目前版本的webpack-dev-server不支持webpack4 升级一波

yarn add webpack-dev-server@3.1.1 -D //我装的是3.1.1的包

不过看了挺多资料只要webpack-dev-server是3.0版本以上好像就兼容大雾反正我是3.0.0-alpha6通过了

3 去除commonchunk plugin 改用 webpack.optimize.SplitChunksPlugin

再一次执行yarn run dev 然后又出错了心里一万个奔腾的野马没办法啊硬着头皮看呗

出错原因

Error: webpack.optimize.CommonsChunkPlugin has been removed, please use config.optimization.splitChunks instead.

　　webpack4废除了很多api 之前配置拆分公共代码打包第三方库贼麻烦然后官方一不做二不休直接废除了之前的又捣鼓了这个webpack.optimize.SplitChunksPlugin

　　然后关于这个插件的使用我也是弄了很久后面跑去官方的example里面去看了一下才有所头绪，如果你之前大致了解原来的commonchunk plugin 直接去看官方的例子你就懂了这里贴一下官方的example链接，其中最重要的就是关于如何打包多文件入口的common-chunk-add-vendor-chunk例子，不多说放链接直接明了的告诉你如何拆分公用代码以及第三方库。

　　至于打包runtime代码 webpack4直接调用新的方法 ok 完事

        new webpack.optimize.RuntimeChunkPlugin({
            name: "manifest"
        }),

　　关于webpack.optimize.SplitChunksPlugin的详细用法我也贴出来有兴趣的同学可以自己琢磨

                new webpack.optimize.SplitChunksPlugin({
                    chunks: "initial", // 必须三选一： "initial" | "all"(默认就是all) | "async"
                    minSize: 0, // 最小尺寸，默认0
                    minChunks: 1, // 最小 chunk ，默认1
                    maxAsyncRequests: 1, // 最大异步请求数， 默认1
                    maxInitialRequests: 1, // 最大初始化请求书，默认1
                    name: function () {
                    }, // 名称，此选项可接收 function
                    cacheGroups: { // 这里开始设置缓存的 chunks
                        priority: 0, // 缓存组优先级
                        vendor: { // key 为entry中定义的 入口名称
                            chunks: "initial", // 必须三选一： "initial" | "all" | "async"(默认就是异步)
                            name: "vendor", // 要缓存的 分隔出来的 chunk 名称
                            minSize: 0,
                            minChunks: 1,
                            enforce: true,
                            maxAsyncRequests: 1, // 最大异步请求数， 默认1
                            maxInitialRequests: 1, // 最大初始化请求书，默认1
                            reuseExistingChunk: true // 可设置是否重用该chunk（查看源码没有发现默认值）
                        }
                    }
                }),

　　最后贴上修改后的webpack.optimize.SplitChunksPlugin的代码

        new webpack.optimize.SplitChunksPlugin({
            cacheGroups: {
                default: {
                    minChunks: 2,
                    priority: -20,
                    reuseExistingChunk: true,
                },
                //打包重复出现的代码
                vendor: {
                    chunks: 'initial',
                    minChunks: 2,
                    maxInitialRequests: 5, // The default limit is too small to showcase the effect
                    minSize: 0, // This is example is too small to create commons chunks
                    name: 'vendor'
                },
                //打包第三方类库
                commons: {
                    name: "commons",
                    chunks: "initial",
                    minChunks: Infinity
                }
            }
        }),

        new webpack.optimize.RuntimeChunkPlugin({
            name: "manifest"
        }),

4 升级happypack插件！！！！！

　　至于为啥用红字如果使用了happypack进行多线程加速打包的小伙伴们千万要记住升级happypack 因为我卡在这里开了很久后面看了别人的配置才知道happypack也不兼容需要进行升级泪奔。。。。贴一下当时的错误提示

TypeError: Cannot read property 'length' of undefined 
    at resolveLoader (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\happypack\lib\WebpackUtils.js:138:17)
    at C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\happypack\lib\WebpackUtils.js:126:7
    at C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\happypack\node_modules\async\lib\async.js:713:13

解决办法：升级呗

yarn add happypack@next -D

　5 剩下的问题大部分都是因为当前的包与webpack4不兼容这里就直接贴出来了

  var outputName = compilation.mainTemplate.applyPluginsWaterfall('asset-path', outputOptions.filename, {
                                                  ^

TypeError: compilation.mainTemplate.applyPluginsWaterfall is not a function
    at C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\html-webpack-plugin\lib\compiler.js:81:51
    at compile (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\webpack\lib\Compiler.js:240:11)
    at hooks.afterCompile.callAsync.err (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\webpack\lib\Compiler.js:488:14)

解决办法：升级html-webpack-plugin

1 yarn add webpack-contrib/html-webpack-plugin -D

最后 extract-text-webpack-plugin和sass-loader也需要进行升级具体我会在最后贴出我的webpack4 demo 大家看着安装哈

6 最后配置完成测试一哈

开发环境下

yarn run start ok 效果没问题看一下构建时间 9891ms 对比图中的webpack3 17161ms

:\Users\hboxs022\Desktop\webpack4>yarn run dev
yarn run v1.3.2
$ set NODE_ENV=dev && webpack-dev-server
Happy[js]: Version: 5.0.0-beta.3. Threads: 6 (shared pool)
(node:2060) DeprecationWarning: Tapable.plugin is deprecated. Use new API on `.hooks` instead
i ｢wds｣: Project is running at http://localhost:8072/
i ｢wds｣: webpack output is served from /
i ｢wds｣: Content not from webpack is served from C:\Users\hboxs022\Desktop\webpack4\src
Happy[js]: All set; signaling webpack to proceed.
Happy[css]: Version: 5.0.0-beta.3. Threads: 6 (shared pool)
Happy[css]: All set; signaling webpack to proceed.
(node:2060) DeprecationWarning: Tapable.apply is deprecated. Call apply on the plugin directly instead
i ｢wdm｣: wait until bundle finished: /page/index.html
i ｢wdm｣: Hash: 1911cfc871cd5dc27aca
Version: webpack 4.1.1
Time: 9891ms
Built at: 2018-3-28 18:49:25