Make CSS optimization actually work.

package.json

@@ -38,6 +38,7 @@
     "case-sensitive-paths-webpack-plugin": "^2.1.2",
     "chalk": "^2.4.1",
     "css-loader": "^1.0.0",
+    "cssnano": "^4.0.1",
     "debug": "^3.1.0",
     "eslint": "4",
     "eslint-config-airbnb-base": "^13.0.0",
@@ -53,9 +54,11 @@
     "nodemon": "^1.18.1",
     "normalize-scss": "^7.0.1",
     "npm-run-all": "^4.1.3",
+    "optimize-css-assets-webpack-plugin": "^4.0.3",
     "postcss-import": "^11.1.0",
     "postcss-loader": "^2.1.6",
     "postcss-preset-env": "^5.2.1",
+    "postcss-safe-parser": "^3.0.1",
     "progress-bar-webpack-plugin": "^1.11.0",
     "resolve-url-loader": "^2.3.0",
     "responsive-loader": "^1.1.0",
@@ -76,5 +79,8 @@
   },
   "dependencies": {
     "typeface-orbitron": "^0.0.54"
+  },
+  "resolutions": {
+    "caniuse-api": "3.0.0"
   }
 }

webpack.config.babel.js

@@ -15,12 +15,18 @@ import { isatty } from 'tty';
 import chalk from 'chalk';
 import _debug from 'debug';
 // import slash from 'slash';
+
+import cssnano from 'cssnano';
+
 import CaseSensitivePathsPlugin from 'case-sensitive-paths-webpack-plugin';
 // import ExtractTextPlugin from 'extract-text-webpack-plugin';
 import MiniCssExtractPlugin from 'mini-css-extract-plugin';
 import HtmlPlugin from 'html-webpack-plugin';
 import ProgressBarPlugin from 'progress-bar-webpack-plugin';
 import UglifyJsPlugin from 'uglifyjs-webpack-plugin';
+import OptimizeCssAssetsPlugin from 'optimize-css-assets-webpack-plugin';
+
+import postcssSafeParser from 'postcss-safe-parser';
 
 import Environment from './config/webpack/environment';
 
@@ -263,7 +269,6 @@ export default (options, { mode }) => {
 
       // Production builds
       ...[
-      // JavaScript minification
         new LoaderOptionsPlugin({ debug: false, minimize: true }),
 
         // Hoisting
@@ -319,6 +324,15 @@ export default (options, { mode }) => {
           },
           sourceMap: true,
         }),
+        new OptimizeCssAssetsPlugin({
+          assetNameRegExp: /\.css$/gi,
+          cssProcessor: cssnano,
+          cssProcessorOptions: {
+            parser: postcssSafeParser,
+            discardComments: { removeAll: true },
+          },
+          canPrint: true,
+        }),
       ],
     },
     devtool: server ? 'cheap-module-source-map' : 'source-map',