webpack live hot reload for sass

Question

I am building a workflow for a react starter and would like to have my browser auto reload when I make a change to my scss files.

Currently, webpack will hot reload when I make a change in my index.js file (set as my entry point). However when I change/add scss code in my scss file, it gets compiled, but the css doesn't get output anywhere and does not trigger a browser reload.

I am new to webpack would really appreciate some insight here.

Here is my webpack.config.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ExtractTextPlugin = require('extract-text-webpack-plugin');

module.exports = {
    entry: ['./src/js/index.js', './src/scss/style.scss'],
    output: {
        path: path.join(__dirname, 'dist'),
        filename: 'js/index_bundle.js',
    },
    module: {
        rules: [
            {
                test: /\.js$/,
                exclude: /node_modules/,
                use: {
                    loader: 'babel-loader'
                }
            },
            {
                test: /\.css$/,
                use: ['style-loader', 'css-loader']
            },
            {
                test: /\.scss$/,
                use: [
                    {
                        loader: 'file-loader',
                        options: {
                            name: '[name].css',
                            outputPath: 'css/'
                        }
                    },
                    {
                        loader: 'extract-loader'
                    },
                    {
                        loader: 'css-loader'
                    },
                    {
                        loader: 'postcss-loader'
                    },
                    {
                        loader: 'sass-loader'
                    }
                ]
            }
        ]
    },
    plugins: [
        new HtmlWebpackPlugin({
            template: './src/index.html'    
        })
    ]
}

My index.js entry point file

import React from 'react';
import ReactDOM from 'react-dom';
import App from '../components/App';


ReactDOM.render(
    <App/>,
    document.getElementById('App')
);

And my App component

import React, {Component} from 'react';
import '../../dist/css/style.css';



class App extends Component {
    render() {
        return (
            <div>
                <p>Test</p>         
            </div>
        )
    }
}

export default App;

Answer 1

Actually, style-loader is the one that is responsible for CSS HMR.

You should add it at the end of the style pipeline, only for dev. For production, you can remain your config.

It should look something like that:

const devMode = process.env.NODE_ENV !== 'production'

{
  test: /\.scss$/,
  use: [
    devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
    {
      loader: 'css-loader'
    },
    {
      loader: 'postcss-loader'
    },
    {
      loader: 'sass-loader'
    }
  ]
}

Pay attention, the best practice of extracting css into a separate file is to use MiniCssExtractPlugin if you are using webpack 4, or ExtractTextWebpackPlugin, if you are using webpack < 4.