Allow nested objects with similar keys.

Fixes #206

Author: leebyron

src/validation/__tests__/UniqueInputFieldNames.js

@@ -48,6 +48,22 @@ describe('Validate: Unique input field names', () => {
     `);
   });
 
+  it('allows for nested input objects with similar fields', () => {
+    expectPassesRule(UniqueInputFieldNames, `
+      {
+        field(arg: {
+          deep: {
+            deep: {
+              id: 1
+            }
+            id: 1
+          }
+          id: 1
+        })
+      }
+    `);
+  });
+
   it('duplicate input object fields', () => {
     expectFailsRule(UniqueInputFieldNames, `
       {

src/validation/rules/UniqueInputFieldNames.js

@@ -22,10 +22,18 @@ export function duplicateInputFieldMessage(fieldName: any): string {
  * uniquely named.
  */
 export function UniqueInputFieldNames(): any {
-  var knownNames = Object.create(null);
+  let knownNameStack = [];
+  let knownNames = Object.create(null);
+
   return {
-    ObjectValue() {
-      knownNames = Object.create(null);
+    ObjectValue: {
+      enter() {
+        knownNameStack.push(knownNames);
+        knownNames = Object.create(null);
+      },
+      leave() {
+        knownNames = knownNameStack.pop();
+      }
     },
     ObjectField(node) {
       var fieldName = node.name.value;