Support source maps for scss in dev environments (#8638)

Author: mkorostoff

packages/react-scripts/config/webpack.config.js

@@ -123,7 +123,7 @@ module.exports = function(webpackEnv) {
             // which in turn let's users customize the target behavior as per their needs.
             postcssNormalize(),
           ],
-          sourceMap: isEnvProduction && shouldUseSourceMap,
+          sourceMap: isEnvProduction ? shouldUseSourceMap : isEnvDevelopment,
         },
       },
     ].filter(Boolean);
@@ -132,7 +132,7 @@ module.exports = function(webpackEnv) {
         {
           loader: require.resolve('resolve-url-loader'),
           options: {
-            sourceMap: isEnvProduction && shouldUseSourceMap,
+            sourceMap: isEnvProduction ? shouldUseSourceMap : isEnvDevelopment,
           },
         },
         {
@@ -498,7 +498,7 @@ module.exports = function(webpackEnv) {
               exclude: cssModuleRegex,
               use: getStyleLoaders({
                 importLoaders: 1,
-                sourceMap: isEnvProduction && shouldUseSourceMap,
+                sourceMap: isEnvProduction ? shouldUseSourceMap : isEnvDevelopment,
               }),
               // Don't consider CSS imports dead code even if the
               // containing package claims to have no side effects.
@@ -512,7 +512,7 @@ module.exports = function(webpackEnv) {
               test: cssModuleRegex,
               use: getStyleLoaders({
                 importLoaders: 1,
-                sourceMap: isEnvProduction && shouldUseSourceMap,
+                sourceMap: isEnvProduction ? shouldUseSourceMap : isEnvDevelopment,
                 modules: {
                   getLocalIdent: getCSSModuleLocalIdent,
                 },
@@ -527,7 +527,7 @@ module.exports = function(webpackEnv) {
               use: getStyleLoaders(
                 {
                   importLoaders: 3,
-                  sourceMap: isEnvProduction && shouldUseSourceMap,
+                  sourceMap: isEnvProduction ? shouldUseSourceMap : isEnvDevelopment,
                 },
                 'sass-loader'
               ),
@@ -544,7 +544,7 @@ module.exports = function(webpackEnv) {
               use: getStyleLoaders(
                 {
                   importLoaders: 3,
-                  sourceMap: isEnvProduction && shouldUseSourceMap,
+                  sourceMap: isEnvProduction ? shouldUseSourceMap : isEnvDevelopment,
                   modules: {
                     getLocalIdent: getCSSModuleLocalIdent,
                   },