From ad5df215868108c04f944b9af29263f09e5b6fd2 Mon Sep 17 00:00:00 2001
From: Stefan Penner <stefan.penner@gmail.com>
Date: Tue, 14 Oct 2014 20:27:16 -0400
Subject: [PATCH] =?UTF-8?q?ensure=20we=20don=E2=80=99t=20needlessly=20scan?=
 =?UTF-8?q?=20the=20concatenated=20properties=20array?=
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---
 packages/ember-metal/lib/mixin.js                |  6 +++++-
 .../tests/mixin/concatenatedProperties_test.js   | 16 ++++++++++++++++
 packages/ember-runtime/lib/system/core_object.js |  4 +++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/packages/ember-metal/lib/mixin.js b/packages/ember-metal/lib/mixin.js
index 170e7ef8ae8..c925056339d 100644
--- a/packages/ember-metal/lib/mixin.js
+++ b/packages/ember-metal/lib/mixin.js
@@ -194,7 +194,11 @@ function applyConcatenatedProperties(obj, key, value, values) {
 
   if (baseValue) {
     if ('function' === typeof baseValue.concat) {
-      return baseValue.concat(value);
+      if (value === null || value === undefined) {
+        return baseValue;
+      } else {
+        return baseValue.concat(value);
+      }
     } else {
       return makeArray(baseValue).concat(value);
     }
diff --git a/packages/ember-metal/tests/mixin/concatenatedProperties_test.js b/packages/ember-metal/tests/mixin/concatenatedProperties_test.js
index f4b87b0801b..e348b83e77f 100644
--- a/packages/ember-metal/tests/mixin/concatenatedProperties_test.js
+++ b/packages/ember-metal/tests/mixin/concatenatedProperties_test.js
@@ -15,6 +15,22 @@ test('defining concatenated properties should concat future version', function()
   deepEqual(Ember.get(obj, 'foo'), ['a', 'b', 'c', 'd', 'e', 'f']);
 });
 
+test('defining concatenated properties should concat future version', function() {
+
+  var MixinA = Ember.Mixin.create({
+    concatenatedProperties: null,
+  });
+
+  var MixinB = Ember.Mixin.create({
+    concatenatedProperties: null,
+  });
+
+  var obj = Ember.mixin({}, MixinA, MixinB);
+
+  deepEqual(obj.concatenatedProperties, []);
+});
+
+
 test('concatenatedProperties should be concatenated', function() {
 
   var MixinA = Ember.Mixin.create({
diff --git a/packages/ember-runtime/lib/system/core_object.js b/packages/ember-runtime/lib/system/core_object.js
index c565317359a..319502f36c6 100644
--- a/packages/ember-runtime/lib/system/core_object.js
+++ b/packages/ember-runtime/lib/system/core_object.js
@@ -132,7 +132,9 @@ function makeCtor() {
                        "time, when Ember.ActionHandler is used (i.e. views, " +
                        "controllers & routes).", !((keyName === 'actions') && ActionHandler.detect(this)));
 
-          if (concatenatedProperties && indexOf(concatenatedProperties, keyName) >= 0) {
+          if (concatenatedProperties && 
+              concatenatedProperties.length > 0 &&
+              indexOf(concatenatedProperties, keyName) >= 0) {
             var baseValue = this[keyName];
 
             if (baseValue) {