shop在webpack4的升级过程被HMR问题卡了很久，最近终于解决，有时间重新梳理并对升级过程踩的坑做下笔记。
- 把webpack、webpack-dev-middleware、webpack-dev-server、webpack-hot-middleware都升级到最新版本。
npm install webpack webpack-dev-middleware webpack-dev-server webpack-hot-middleware --save-dev
- 升级loaders，修改webpack loader的rules配置结构，从webpack2开始loader已经全部改成了rules的写法。
npm install bundle-loader css-loader file-loader less-loader postcss-loader sass-loader style-loader url-loader postcss-modules-values less precss base64-loader
mode: 'development',
loaders: [
{
test: /\.js$/,
loaders: ['babel'],
exclude: /node_modules/
}
...
]
- 重新打包Dll。
- 增加webpack mode配置。
- postcss的配置从webpack配置里放到了单独的文件postcss.config.js。
- 去除OccurenceOrderPlugin、DedupePlugin和CommonsChunkPlugin等插件。
- ExtractTextWebpackPlugin调整，选用新的CSS文件提取插件mini-css-extract-plugin。
- fs.walk在fs-extra 2.0.0以后移除，换成klaw。
- res.send(status, content) => res.status(status).send(content)
webpack 4取消了四个常用的用于性能优化的plugin（UglifyjsWebpackPlugin，CommonsChunkPlugin，ModuleConcatenationPlugin，NoEmitOnErrorsPlugin），转而提供了一个名为optimization的配置项，用于接手以上四位的工作。在webpack4，我们熟悉的CommonsChunkPlugin被splitChunks取代，另外runtimeChunk用于分开打包runtime。DllPlugin因为无法应用tree shaking，一般服务于develop环境。shop可以考虑优化成production环境使用splitChunks和runtimeChunk，develop环境使用DllPlugin。
- 升级babel8
npm uninstall babel-core babel-eslint babel-loader babel-plugin-transform-class-properties babel-plugin-transform-decorators-legacy babel-plugin-transform-object-rest-spread babel-plugin-transform-omodule-variable babel-polyfill babel-preset-env babel-preset-react babel-preset-react-hmre --save-dev
npm i @babel/core @babel/plugin-proposal-class-properties @babel/plugin-proposal-decorators @babel/plugin-proposal-export-default-from @babel/plugin-proposal-export-namespace-from @babel/plugin-syntax-dynamic-import @babel/plugin-transform-runtime @babel/preset-env @babel/preset-react @babel/runtime babel-eslint babel-loader babel-plugin-dynamic-import-node babel-plugin-syntax-dynamic-import babel-plugin-transform-omodule-variable --save-dev
修改babel配置
{
"presets": ["@babel/preset-react",
[
"@babel/preset-env",
{
"loose": true
}
]
],
"plugins": [
"transform-omodule-variable",
["@babel/plugin-proposal-decorators", { "legacy": true }],
"@babel/plugin-proposal-class-properties",
"@babel/plugin-proposal-export-default-from",
"@babel/plugin-proposal-export-namespace-from",
"@babel/plugin-transform-runtime",
["react-hot-loader/babel"],
["@babel/plugin-syntax-dynamic-import"]
]
}
enable inline javascript for less-loader
{
test: /\.less$/,
use: [
'style-loader',
'css-loader',
'postcss-loader',
{
loader: 'less-loader',
options: {
javascriptEnabled: true
}
}
]
}
- It's no longer allowed to omit the '-loader' suffix when using loaders.
You need to specify 'bundle-loader' instead of 'bundle'
按提示解决了一些小问题，这时候项目应该可以跑起来了。接下来说说HMR的解决方案。HMR之所以会出问题是因为omodule的require.context涉及到code splitting，更新之后的hot-update过程中，动态加载的组件不知道怎么刷新自己导致的。按照react-hot-loader的文档给组件包上RHL friendly的兼容库（例如 Loadable Components）之后还是无法解决。几经周折，最后尝试出在所有动态分割的组件加上hot方法：
- babel-preset-react-hmre => react-hot-loader
- require => import，RHL just support hot import component
- '../../configs/' + props.productId + '.js' =>
../../configs/${props.productId}.js- getComponent =>component (async)
- route.js里，对每个component包上hot方法
process-update.js:22 Ignored an update to unaccepted module ./node_modules/babel-loader/lib/index.js!./src/omodules/one-page-insurance/pages/OnePageDetail.js -> ./node_modules/bundle-loader/index.js!./src/omodules/one-page-insurance/pages/OnePageDetail.js -> ./src/omodules/one-page-insurance/route.js -> ./src/omodules/one-page-insurance/omodule.js -> ./src sync recursive ^\.\/omodules\/((?!\/)[\s\S])+\/omodule\.js$ -> ./src/omodule.js -> ./src/root/store/configureStore.dev.js -> ./src/root/store/configureStore.js -> ./src/root/index.js -> 0
onUnaccepted @ process-update.js:22
hotApply @ bootstrap:502
cb @ process-update.js:66
(anonymous) @ process-update.js:82
Promise.then (async)
check @ process-update.js:81
./node_modules/webpack-hot-middleware/process-update.js.module.exports @ process-update.js:42
processMessage @ client.js:268
handleMessage @ client.js:136
handleMessage @ client.js:99
process-update.js:95 [HMR] The following modules couldn't be hot updated: (Full reload needed)
This is usually because the modules which have changed (and their parents) do not know how to hot reload themselves. See https://webpack.js.org/concepts/hot-module-replacement/ for more details.
/**
* omodule 描述文件
* 大多数情况不需要修改该文件。新建一个模块，复制粘贴该文件即可
* {
* route,
* reducer, //一个omodule模块可以没有reducer
* childOmodules
* }
*
*/
import { hot } from 'react-hot-loader/root'
export const namespace = __omodule_namespace
const routes = require('./route').default
routes.childRoutes = routes.childRoutes.map(({ path, component }) => {
return {
path,
component: hot(component)
}
})
const omodule = {
route: routes,
// 异步reducer写法：
// 一般情况下都推荐用异步reducer，
// 只有当进入该omudle模块下的路由时异步reducer才会被加载
//
reducer: cb => {
import('./reducer/index.js').then(function(reducerFun) {
const reducer = {}
reducer[namespace] = reducerFun.default
cb(null, reducer)
})
},
// 同步reducer写法： 整个项目初始化就会加载该reducer
//
// reducer: {
// [`${namespace}`]: require('./reducer').default
// },
childOmodules: (r => {
return r.keys().map(key => r(key).default)
})(require.context('./', true, /^\.\/omodules\/((?!\/)[\s\S])+\/omodule\.js$/))
}
export default omodule
升级过程中发现webpack由4.23升级到4.29之后会报错，缺少解析动态import的loader，应该是plugin-syntax-dynamic-import不兼容4.29的webpack，回退到4.23。
HMR参考资料
https://github.com/gaearon/react-hot-loader
https://github.com/gaearon/react-hot-boilerplate
https://github.com/gaearon/react-hot-loader/blob/master/docs/Troubleshooting.md
https://webpack.docschina.org/guides/hot-module-replacement
https://github.com/gaearon/react-hot-loader/issues/288
https://github.com/gaearon/react-hot-loader/issues/249
其他
https://github.com/jprichardson/node-fs-extra/issues/338
https://segmentfault.com/a/1190000005614604
http://www.voidcn.com/article/p-sfoxvjwp-bbs.html
http://acgtofe.com/posts/2016/02/full-live-reload-for-express-with-webpack
https://zhuanlan.zhihu.com/p/35407642
