fix(copy): support copying properties with a null prototype

Partially cherry-picked from f7b9997

Author: petebacondarwin

src/Angular.js

@@ -36,6 +36,7 @@
   isUndefined: true,
   isDefined: true,
   isObject: true,
+  isBlankObject: true,
   isString: true,
   isNumber: true,
   isDate: true,
@@ -172,6 +173,7 @@ var
     splice            = [].splice,
     push              = [].push,
     toString          = Object.prototype.toString,
+    getPrototypeOf    = Object.getPrototypeOf,
     ngMinErr          = minErr('ng'),
 
     /** @name angular */
@@ -461,6 +463,16 @@ function isObject(value) {
 }
 
 
+/**
+ * Determine if a value is an object with a null prototype
+ *
+ * @returns {boolean} True if `value` is an `Object` with a null prototype
+ */
+function isBlankObject(value) {
+  return value !== null && typeof value === 'object' && !getPrototypeOf(value);
+}
+
+
 /**
  * @ngdoc function
  * @name angular.isString
@@ -742,7 +754,7 @@ function copy(source, destination, stackSource, stackDest) {
         destination = new RegExp(source.source, source.toString().match(/[^\/]*$/)[0]);
         destination.lastIndex = source.lastIndex;
       } else if (isObject(source)) {
-        var emptyObject = Object.create(Object.getPrototypeOf(source));
+        var emptyObject = Object.create(getPrototypeOf(source));
         destination = copy(source, emptyObject, stackSource, stackDest);
       }
     }
@@ -761,7 +773,7 @@ function copy(source, destination, stackSource, stackDest) {
       stackDest.push(destination);
     }
 
-    var result;
+    var result, key;
     if (isArray(source)) {
       destination.length = 0;
       for (var i = 0; i < source.length; i++) {
@@ -781,21 +793,40 @@ function copy(source, destination, stackSource, stackDest) {
           delete destination[key];
         });
       }
-      for (var key in source) {
-        if (source.hasOwnProperty(key)) {
-          result = copy(source[key], null, stackSource, stackDest);
-          if (isObject(source[key])) {
-            stackSource.push(source[key]);
-            stackDest.push(result);
+      if (isBlankObject(source)) {
+        // createMap() fast path --- Safe to avoid hasOwnProperty check because prototype chain is empty
+        for (key in source) {
+          putValue(key, source[key], destination, stackSource, stackDest);
+        }
+      } else if (source && typeof source.hasOwnProperty === 'function') {
+        // Slow path, which must rely on hasOwnProperty
+        for (key in source) {
+          if (source.hasOwnProperty(key)) {
+            putValue(key, source[key], destination, stackSource, stackDest);
+          }
+        }
+      } else {
+        // Slowest path --- hasOwnProperty can't be called as a method
+        for (key in source) {
+          if (hasOwnProperty.call(source, key)) {
+            putValue(key, source[key], destination, stackSource, stackDest);
           }
-          destination[key] = result;
         }
       }
       setHashKey(destination,h);
     }
-
   }
   return destination;
+
+  function putValue(key, val, destination, stackSource, stackDest) {
+    // No context allocation, trivial outer scope, easily inlined
+    var result = copy(val, null, stackSource, stackDest);
+    if (isObject(val)) {
+      stackSource.push(val);
+      stackDest.push(result);
+    }
+    destination[key] = result;
+  }
 }
 
 /**

test/AngularSpec.js

@@ -370,6 +370,21 @@ describe('angular', function() {
       expect(copy(undefined, [1,2,3])).toEqual([]);
       expect(copy({0: 1, 1: 2}, [1,2,3])).toEqual([1,2]);
     });
+
+    it('should copy objects with no prototype parent', function() {
+      var obj = extend(Object.create(null), {
+        a: 1,
+        b: 2,
+        c: 3
+      });
+      var dest = copy(obj);
+
+      expect(Object.getPrototypeOf(dest)).toBe(null);
+      expect(dest.a).toBe(1);
+      expect(dest.b).toBe(2);
+      expect(dest.c).toBe(3);
+      expect(Object.keys(dest)).toEqual(['a', 'b', 'c']);
+    });
   });
 
   describe("extend", function() {