Webpack 4 + Express + Hot module reloading without middleware

gistfile1.txt

//*********server.js*********

const express = require('express')
const path = require('path')

const app = express()
const port = process.env.PORT || 3000

app.use(express.static(path.join(__dirname, 'public/build')))
app.use('/api', someApiRoutes)
app.get('*', (req, res) => {
  res.sendFile(path.join(__dirname, 'public/build/index.html'));
});

app.listen(port, () => {
  console.log(`Server Started at port ${port}`);
});

//*********webpack.config.js*********

const path = require('path')
const webpack = require('webpack')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const MiniCssExtractPlugin = require("mini-css-extract-plugin")
//const ExtractTextPlugin = require('extract-text-webpack-plugin')
const autoprefixer = require('autoprefixer')
const chalk = require('chalk')

let config
let setPlugins
let setStyleRules
let isDev
let publicPath

process.env.NODE_ENV = process.env.NODE_ENV || 'development'
isDev = process.env.NODE_ENV !== 'production'
publicPath = '/'

console.log('environment: ' + chalk.bgGreen(` ${process.env.NODE_ENV} `) + '\n')

//plugins assigned to a variable so dev and prod can each have their own plugins
setPlugins = () => {
  if (!isDev) { //prod
    return [
      new webpack.DefinePlugin({
        'process.env': { NODE_ENV: JSON.stringify('production') }
      }),
      new HtmlWebpackPlugin({
        template: './app/index.tpl.html',
        inject: 'head',
        filename: 'index.html'
      }),
      new MiniCssExtractPlugin({
        filename: path.join('css','[name].css')
      }),
      //new webpack.optimize.CommonsChunkPlugin({
      //  name: 'vendor',
      //  minChunks: function (module) {
      //    return module.context && (module.context.indexOf('node_modules') !== -1 || module.context.indexOf('_lib') !== -1);
      //  }
      //})
    ]
  }
  else { //dev
    return [
      new HtmlWebpackPlugin({
        template: './app/index.tpl.html',
        inject: 'head',
        filename: 'index.html'
      })
    ]
  }
}

// css/less rules object assigned to a variable so we can use it in both dev and prod flow
setStyleRules = () => {

  let loaders = isDev ? ['style-loader'] : [MiniCssExtractPlugin.loader]

  loaders.push(
    {
      loader: 'css-loader',
      options: {
        sourceMap: isDev,
      }
    },
    {
      loader: 'sass-loader',
      options: {
        sourceMap: isDev,
      },
    },
    {
      loader: 'postcss-loader',
      options: {
        plugins: [autoprefixer],
        minimize: !isDev
      },
    }
  )

  return loaders
}

//main config
config = {
  mode: isDev ? 'development' : 'production',
  entry: {
    app: ['babel-polyfill', path.join(__dirname, 'app', 'index.jsx')]
  },
  resolve: {
    extensions: ['.js', '.jsx']
  },
  optimization: {
    splitChunks: {
      // include all types of chunks
      chunks: 'all',
      cacheGroups: {
        commons: {
          name: 'commons',
          chunks: 'initial',
          minChunks: 2
        },
        vendors: {
          test: /[\\/]node_modules[\\/]/,
          name: 'vendors',
          chunks: 'all'
        }
      }
    }
  },
  module: {
    rules: [
      //*** js
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader'
        }
      },
      //*** styles
      {
        test: /\.s?css$/,
        use: setStyleRules()
      },
      //*** bundled images
      {
        test: /\.(png|jpg|svg)$/,
        use: {
          loader: 'file-loader',
          options: {
            //outputPath: '',
            name: 'img/[name].[ext]'
          }
        }
      }
    ]
  },
  plugins: setPlugins(),
  output: {
    path: path.join(__dirname, 'public'),
    filename: path.join('js', '[name].js'),
    publicPath: publicPath
  },
  devServer: {
    historyApiFallback: true,
    publicPath: publicPath,
    hot: true,
    proxy: {
      '/api': {
        target: 'http://localhost:3000'
      }
    }
  },
  devtool: isDev ? 'eval-sourcemap' : false
}

module.exports = config

*********package.json*********

{
  "name": "fullstack-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "export NODE_ENV=development && npm run devclient",
    "build": "export NODE_ENV=production && rm -rf ./build && npm run client && npm run server",
    "devserver": "nodemon server.js",
    "devclient": "webpack-dev-server --open --hot",
    "server": "node server.js",
    "client": "webpack -p",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "samelwitt@gmail.com",
  "license": "ISC",
  "dependencies": {
    "autoprefixer": "^8.6.3",
    "babel-core": "^6.26.3",
    "babel-loader": "^7.1.4",
    "babel-plugin-transform-class-properties": "^6.24.1",
    "babel-polyfill": "^6.26.0",
    "babel-preset-env": "^1.7.0",
    "babel-preset-react": "^6.24.1",
    "body-parser": "^1.18.3",
    "chalk": "^2.4.1",
    "copy-webpack-plugin": "^4.5.1",
    "css-loader": "^2.1.1",
    "dotenv": "^6.0.0",
    "express": "^4.16.3",
    "file-loader": "^1.1.11",
    "html-webpack-plugin": "^3.2.0",
    "mini-css-extract-plugin": "^0.4.0",
    "mongodb": "^3.1.8",
    "node-sass": "^4.12.0",
    "postcss-loader": "^2.1.5",
    "prop-types": "^15.6.2",
    "react": "^16.4.1",
    "react-dom": "^16.4.1",
    "react-hot-loader": "^4.3.3",
    "react-json-view": "latest",
    "react-router-dom": "^4.3.1",
    "sass-loader": "^7.1.0",
    "uuid": "^3.2.1",
    "webpack": "^4.12.0",
    "webpack-cli": "^3.0.8"
  },
  "devDependencies": {
    "style-loader": "^0.21.0",
    "webpack-dev-server": "^3.3.1"
  }
}
  
*********babel.rc*********

...
  "plugins": [
    "react-hot-loader/babel"
  ]
...

*********components/App.jsx*********

import React from 'react'
import { hot } from 'react-hot-loader'

class App extends React.Component {

  state = {}

  // lifecycle
  componentWillMount () {
    //
  }

  // main render method
  render () {
    return (<div>App!</div>)
  }
}

export default hot(module)(App)