Webpack 4 devtool option does not work with webpack-dev-server

So, after a long tried and error, I finally got help from one of webpack mainteiners. The main issue was eslint. If you load it as a loader, it creates unexpected behaviour. By deleting the eslint from webpack loaders for js you can fix that.

The webpack setup before:

// webpack v4
const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const WebpackMd5Hash = require('webpack-md5-hash');
const CleanWebpackPlugin = require('clean-webpack-plugin');

const baseConfig = {
  entry: { main: './src/index.js' },
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].[hash].js'
  },
  devServer: {
    contentBase: './dist',
    hot: true,
    open: true
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        **use: [
          { loader: 'babel-loader' },
          {
            loader: 'eslint-loader',
            options: { formatter: require('eslint/lib/formatters/stylish') }
          }**
        ]
      }
    ]
  },
  plugins: [
    new CleanWebpackPlugin('dist'),
    new HtmlWebpackPlugin({
      inject: false,
      hash: true,
      template: './src/index.html',
      filename: 'index.html'
    }),
    new WebpackMd5Hash()
  ]
};

if (process.env.NODE_ENV === 'development') {
  baseConfig.devtool = 'inline-source-map';
}

module.exports = baseConfig

the webpack that works after:

// webpack v4
const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const WebpackMd5Hash = require('webpack-md5-hash');
const CleanWebpackPlugin = require('clean-webpack-plugin');
module.exports = {
  entry: { main: './src/index.js' },
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].[hash].js'
  },
  devtool: 'cheap-module-source-map',
  devServer: {
    contentBase: './dist',
    hot: true,
    open: true
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        **use: [{ loader: 'babel-loader' }]**
      }
    ]
  },
  plugins: [
    new CleanWebpackPlugin('dist'),
    new HtmlWebpackPlugin({
      inject: false,
      hash: true,
      template: './src/index.html',
      filename: 'index.html'
    }),
    new WebpackMd5Hash()
  ]
};

my packeje.json looks like:

{
  "name": "post",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "build": "webpack --mode=production",
    "start": "NODE_ENV=development webpack-dev-server --mode=development --hot"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-cli": "^6.26.0",
    "babel-core": "^6.26.0",
    "babel-loader": "^7.1.4",
    "babel-preset-env": "^1.6.1",
    "babel-preset-react": "^6.24.1",
    "babel-runtime": "^6.26.0",
    "clean-webpack-plugin": "^0.1.19",
    "eslint": "^4.19.1",
    "eslint-config-prettier": "^2.9.0",
    "eslint-loader": "^2.0.0",
    "eslint-plugin-prettier": "^2.6.0",
    "eslint-plugin-react": "^7.7.0",
    "html-webpack-plugin": "^3.2.0",
    "prettier": "^1.12.1",
    "react": "^16.3.2",
    "react-dom": "^16.3.2",
    "webpack": "^4.6.0",
    "webpack-cli": "^2.0.13",
    "webpack-md5-hash": "0.0.6"
  },
  "dependencies": {
    "webpack-dev-server": "^3.1.3"
  }
}

See also the suggestions from the issue that was created on my branch: https://github.com/marharyta/webpack-4.6.0-test

Tags:

Npm

Source Maps

Reactjs

Webpack

Webpack Dev Server

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