From 16fdc3d253f0ba7003e64bf73675d0728de97da0 Mon Sep 17 00:00:00 2001
From: Julien Sanchez <julien.sanchez@gmail.com>
Date: Thu, 21 Nov 2013 09:20:54 +0100
Subject: [PATCH] fix(copy): preserve prototype chain when copying object

So far, angular.copy was copying all properties including those from
prototype chain and was losing the whole prototype chain (except for Date,
Regexp, and Array).

Deep copy should exclude properties from the prototype chain because it
is useless to do so. When modified, properties from prototype chain are
overwritten on the object itself and will be deeply copied then.

Moreover, preserving prototype chain allows instanceof operator to be
consistent between the source object and the copy.
Before this change,

    var Foo = function() {};
    var foo = new Foo();
    var fooCopy = angular.copy(foo);
    foo instanceof Foo; // => true
    fooCopy instanceof Foo; // => false

Now,

    foo instanceof Foo; // => true
    fooCopy instanceof Foo; // => true

The new behaviour is useful when using $http transformResponse. When
receiving JSON data, we could transform it and instantiate real object
"types" from it. The transformed response is always copied by Angular.
The old behaviour was losing the whole prototype chain and broke all
"types" from third-party libraries depending on instanceof.
---
 src/Angular.js      | 15 +++++++++------
 test/AngularSpec.js | 10 ++++++++++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/Angular.js b/src/Angular.js
index 8daf1e417140..a08bda672099 100644
--- a/src/Angular.js
+++ b/src/Angular.js
@@ -772,7 +772,8 @@ function copy(source, destination, stackSource, stackDest) {
       } else if (isRegExp(source)) {
         destination = new RegExp(source.source);
       } else if (isObject(source)) {
-        destination = copy(source, {}, stackSource, stackDest);
+        var emptyObject = Object.create(Object.getPrototypeOf(source));
+        destination = copy(source, emptyObject, stackSource, stackDest);
       }
     }
   } else {
@@ -807,12 +808,14 @@ function copy(source, destination, stackSource, stackDest) {
         delete destination[key];
       });
       for ( var key in source) {
-        result = copy(source[key], null, stackSource, stackDest);
-        if (isObject(source[key])) {
-          stackSource.push(source[key]);
-          stackDest.push(result);
+        if(source.hasOwnProperty(key)) {
+          result = copy(source[key], null, stackSource, stackDest);
+          if (isObject(source[key])) {
+            stackSource.push(source[key]);
+            stackDest.push(result);
+          }
+          destination[key] = result;
         }
-        destination[key] = result;
       }
       setHashKey(destination,h);
     }
diff --git a/test/AngularSpec.js b/test/AngularSpec.js
index 5d75eb1dca41..fea74f81212a 100644
--- a/test/AngularSpec.js
+++ b/test/AngularSpec.js
@@ -24,6 +24,16 @@ describe('angular', function() {
       expect(copy([], arr)).toBe(arr);
     });
 
+    it("should preserve prototype chaining", function() {
+      var GrandParentProto = {};
+      var ParentProto = Object.create(GrandParentProto);
+      var obj = Object.create(ParentProto);
+      expect(ParentProto.isPrototypeOf(copy(obj))).toBe(true);
+      expect(GrandParentProto.isPrototypeOf(copy(obj))).toBe(true);
+      var Foo = function() {};
+      expect(copy(new Foo()) instanceof Foo).toBe(true);
+    });
+
     it("should copy Date", function() {
       var date = new Date(123);
       expect(copy(date) instanceof Date).toBeTruthy();