Merge pull request #190 from haggholm/avoid-useless-mutation

Do not mutate objects when values do not change

Author: JamesMessinger

lib/dereference.js

@@ -57,13 +57,19 @@ function crawl (obj, path, pathFromRoot, parents, $refs, options) {
         if ($Ref.isAllowed$Ref(value, options)) {
           dereferenced = dereference$Ref(value, keyPath, keyPathFromRoot, parents, $refs, options);
           circular = dereferenced.circular;
-          obj[key] = dereferenced.value;
+          // Avoid pointless mutations; breaks frozen objects to no profit
+          if (obj[key] !== dereferenced.value) {
+            obj[key] = dereferenced.value;
+          }
         }
         else {
           if (parents.indexOf(value) === -1) {
             dereferenced = crawl(value, keyPath, keyPathFromRoot, parents, $refs, options);
             circular = dereferenced.circular;
-            obj[key] = dereferenced.value;
+            // Avoid pointless mutations; breaks frozen objects to no profit
+            if (obj[key] !== dereferenced.value) {
+              obj[key] = dereferenced.value;
+            }
           }
           else {
             circular = foundCircularReference(keyPath, $refs, options);