webpack.config.dev.js

// @remove-on-eject-begin
/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
// @remove-on-eject-end

var path = require('path');
var autoprefixer = require('autoprefixer');
var webpack = require('webpack');
var HtmlWebpackPlugin = require('html-webpack-plugin');
var CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
var WatchMissingNodeModulesPlugin = require('../scripts/utils/WatchMissingNodeModulesPlugin');
var paths = require('./paths');
var env = require('./env');

// This is the development configuration.
// It is focused on developer experience and fast rebuilds.
// The production configuration is different and lives in a separate file.
module.exports = {
  // This makes the bundle appear split into separate modules in the devtools.
  // We don't use source maps here because they can be confusing:
  // https://github.com/facebookincubator/create-react-app/issues/343#issuecomment-237241875
  // You may want 'cheap-module-source-map' instead if you prefer source maps.
  devtool: 'eval',
  // These are the "entry points" to our application.
  // This means they will be the "root" imports that are included in JS bundle.
  // The first two entry points enable "hot" CSS and auto-refreshes for JS.
  entry: [
    // Include WebpackDevServer client. It connects to WebpackDevServer via
    // sockets and waits for recompile notifications. When WebpackDevServer
    // recompiles, it sends a message to the client by socket. If only CSS
    // was changed, the app reload just the CSS. Otherwise, it will refresh.
    // The "?/" bit at the end tells the client to look for the socket at
    // the root path, i.e. /sockjs-node/. Otherwise visiting a client-side
    // route like /todos/42 would make it wrongly request /todos/42/sockjs-node.
    // The socket server is a part of WebpackDevServer which we are using.
    // The /sockjs-node/ path I'm referring to is hardcoded in WebpackDevServer.
    require.resolve('webpack-dev-server/client') + '?/',
    // Include Webpack hot module replacement runtime. Webpack is pretty
    // low-level so we need to put all the pieces together. The runtime listens
    // to the events received by the client above, and applies updates (such as
    // new CSS) to the running application.
    require.resolve('webpack/hot/dev-server'),
    // We ship a few polyfills by default.
    require.resolve('./polyfills'),
    // Finally, this is your app's code:
    paths.appIndexJs
    // We include the app code last so that if there is a runtime error during
    // initialization, it doesn't blow up the WebpackDevServer client, and
    // changing JS code would still trigger a refresh.
  ],
  output: {
    // Next line is not used in dev but WebpackDevServer crashes without it:
    path: paths.appBuild,
    // Add /* filename */ comments to generated require()s in the output.
    pathinfo: true,
    // This does not produce a real file. It's just the virtual path that is
    // served by WebpackDevServer in development. This is the JS bundle
    // containing code from all our entry points, and the Webpack runtime.
    filename: 'static/js/bundle.js',
    // In development, we always serve from the root. This makes config easier.
    publicPath: '/'
  },
  resolve: {
    // This allows you to set a fallback for where Webpack should look for modules.