Merge pull request #1190 from dballance/master

Add lookaside to `traverse` - Limits DFS revisit

Author: shockey

src/specmap/index.js

@@ -83,6 +83,8 @@ class SpecMap {
     // We might consider making this (traversing & application) configurable later.
     function createKeyBasedPlugin(pluginObj) {
       return function* (patches, specmap) {
+        const traversedRefs = {}
+
         for (const patch of patches.filter(lib.isAdditiveMutation)) {
           yield* traverse(patch.value, patch.path, patch)
         }
@@ -102,9 +104,21 @@ class SpecMap {
             for (const key of Object.keys(obj)) {
               const val = obj[key]
               const updatedPath = path.concat(key)
-
-              if (lib.isObject(val)) {
-                yield* traverse(val, updatedPath, patch)
+              const isObj = lib.isObject(val)
+
+              // If the object has a meta '$$ref' - and store this $$ref
+              // in a lookaside to prevent future traversals of this $ref's tree.
+              const objRef = obj.$$ref
+              const traversed = specmap.allowMetaPatches && traversedRefs[obj.$$ref]
+
+              if (!traversed) {
+                if (isObj) {
+                  // Only store the ref if it exists
+                  if (specmap.allowMetaPatches && objRef) {
+                    traversedRefs[objRef] = true
+                  }
+                  yield* traverse(val, updatedPath, patch)
+                }
               }
 
               if (!isRootProperties && key === pluginObj.key) {