From 34f4a0e42da6831dc4cdc5d9e7728acc99582363 Mon Sep 17 00:00:00 2001
From: Ian Obermiller <iano@fb.com>
Date: Wed, 4 Mar 2015 22:16:51 -0800
Subject: [PATCH] shallowEqual: bail if either argument is falsey

Also add some unit tests.
---
 src/utils/__tests__/shallowEqual-test.js | 71 ++++++++++++++++++++++++
 src/utils/shallowEqual.js                |  5 ++
 2 files changed, 76 insertions(+)
 create mode 100644 src/utils/__tests__/shallowEqual-test.js

diff --git a/src/utils/__tests__/shallowEqual-test.js b/src/utils/__tests__/shallowEqual-test.js
new file mode 100644
index 0000000000..522c62cda8
--- /dev/null
+++ b/src/utils/__tests__/shallowEqual-test.js
@@ -0,0 +1,71 @@
+/**
+ * Copyright 2014-2015, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @emails react-core
+ */
+
+'use strict';
+
+require('mock-modules')
+  .dontMock('shallowEqual');
+
+var shallowEqual;
+
+describe('shallowEqual', function() {
+
+  beforeEach(function() {
+    shallowEqual = require('shallowEqual');
+  });
+
+  it('returns false if either argument is null', function() {
+    expect(shallowEqual(null, {})).toBe(false);
+    expect(shallowEqual({}, null)).toBe(false);
+  });
+
+  it('returns true if both arguments are null or undefined', function() {
+    expect(shallowEqual(null, null)).toBe(true);
+    expect(shallowEqual(undefined, undefined)).toBe(true);
+  });
+
+  it('returns true if arguments are shallow equal', function() {
+    expect(
+      shallowEqual(
+        {a: 1, b: 2, c: 3},
+        {a: 1, b: 2, c: 3}
+      )
+    ).toBe(true);
+  });
+
+  it('returns false if first argument has too many keys', function() {
+    expect(
+      shallowEqual(
+        {a: 1, b: 2, c: 3},
+        {a: 1, b: 2}
+      )
+    ).toBe(false);
+  });
+
+  it('returns false if second argument has too many keys', function() {
+    expect(
+      shallowEqual(
+        {a: 1, b: 2},
+        {a: 1, b: 2, c: 3}
+      )
+    ).toBe(false);
+  });
+
+  it('returns false if arguments are not shallow equal', function() {
+    expect(
+      shallowEqual(
+        {a: 1, b: 2, c: {}},
+        {a: 1, b: 2, c: {}}
+      )
+    ).toBe(false);
+  });
+
+});
diff --git a/src/utils/shallowEqual.js b/src/utils/shallowEqual.js
index 9ff880377f..8b35d0d4dc 100644
--- a/src/utils/shallowEqual.js
+++ b/src/utils/shallowEqual.js
@@ -22,6 +22,11 @@ function shallowEqual(objA, objB) {
   if (objA === objB) {
     return true;
   }
+
+  if (!objA || !objB) {
+    return false;
+  }
+
   var key;
   // Test for A's keys different from B.
   for (key in objA) {