generate source map for uglify if devtool === #source-map (#3451)

* generate source map for uglify if devtool === #source-map

* support different variants of source-map option

* change source map to be likes in official webpack repo
https://github.com/webpack/webpack/blob/master/lib/WebpackOptionsDefaulter.js#L294

* small code cleanup

lib/builder/webpack/client.js

@@ -98,26 +98,6 @@ export default class WebpackClientConfig extends WebpackBaseConfig {
       }
     }
 
-    // Make uglifyjs faster
-    if (!this.options.dev && !config.optimization.minimizer) {
-      // https://github.com/webpack-contrib/uglifyjs-webpack-plugin
-      config.optimization.minimizer = [
-        new UglifyJsWebpackPlugin({
-          parallel: true,
-          cache: this.options.build.cache,
-          sourceMap: false,
-          extractComments: {
-            filename: 'LICENSES'
-          },
-          uglifyOptions: {
-            output: {
-              comments: /^\**!|@preserve|@license|@cc_on/
-            }
-          }
-        })
-      ]
-    }
-
     // Add HMR support
     if (this.options.dev) {
       config.entry = [
@@ -153,6 +133,26 @@ export default class WebpackClientConfig extends WebpackBaseConfig {
       }
     }
 
+    // Make uglifyjs faster
+    if (!this.options.dev && !config.optimization.minimizer) {
+      // https://github.com/webpack-contrib/uglifyjs-webpack-plugin
+      config.optimization.minimizer = [
+        new UglifyJsWebpackPlugin({
+          parallel: true,
+          cache: this.options.build.cache,
+          sourceMap: config.devtool && /source-?map/.test(config.devtool),
+          extractComments: {
+            filename: 'LICENSES'
+          },
+          uglifyOptions: {
+            output: {
+              comments: /^\**!|@preserve|@license|@cc_on/
+            }
+          }
+        })
+      ]
+    }
+
     return config
   }
 }