Switched to webpack@4.12 and UglifyJsWebpackPlugin.

bin/build-ckeditor.sh

@@ -3,7 +3,7 @@
 echo "Building 'build/ckeditor.js'..."
 echo ""
 
-webpack
+webpack --mode production
 
 echo ""
 echo "Done."

package.json

@@ -49,12 +49,12 @@
     "@ckeditor/ckeditor5-theme-lark": "^10.1.0",
     "@ckeditor/ckeditor5-upload": "^10.0.1",
     "@ckeditor/ckeditor5-table": "^10.0.0",
-    "babel-minify-webpack-plugin": "^0.3.0",
-    "postcss-loader": "^2.0.10",
+    "postcss-loader": "^2.1.5",
     "raw-loader": "^0.5.1",
-    "style-loader": "^0.20.3",
-    "webpack": "^3.11.0",
-    "webpack-sources": "1.0.1"
+    "style-loader": "^0.21.0",
+    "uglifyjs-webpack-plugin": "^1.2.7",
+    "webpack": "^4.12.2",
+    "webpack-cli": "^3.0.8"
   },
   "engines": {
     "node": ">=6.0.0",

webpack.config.js

@@ -11,7 +11,7 @@ const path = require( 'path' );
 const webpack = require( 'webpack' );
 const { bundler, styles } = require( '@ckeditor/ckeditor5-dev-utils' );
 const CKEditorWebpackPlugin = require( '@ckeditor/ckeditor5-dev-webpack-plugin' );
-const BabiliPlugin = require( 'babel-minify-webpack-plugin' );
+const UglifyJsWebpackPlugin = require( 'uglifyjs-webpack-plugin' );
 const buildConfig = require( './build-config' );
 
 module.exports = {
@@ -27,19 +27,28 @@ module.exports = {
 		library: buildConfig.moduleName
 	},
 
+	optimization: {
+		minimizer: [
+			new UglifyJsWebpackPlugin( {
+				sourceMap: true,
+				uglifyOptions: {
+					output: {
+						comments: /^\**!/
+					}
+				}
+			} ),
+		]
+	},
+
 	plugins: [
 		new CKEditorWebpackPlugin( {
 			language: buildConfig.config.language,
 			additionalLanguages: 'all'
 		} ),
-		new BabiliPlugin( null, {
-			comments: false
-		} ),
 		new webpack.BannerPlugin( {
 			banner: bundler.getLicenseBanner(),
 			raw: true
-		} ),
-		new webpack.optimize.ModuleConcatenationPlugin()
+		} )
 	],
 
 	module: {