From d33ead3f1692342bc43fb2c96e037836d985bce6 Mon Sep 17 00:00:00 2001
From: Samuel Susla <samuelsusla@fb.com>
Date: Thu, 27 Feb 2020 05:40:02 -0800
Subject: [PATCH] Fix matricesDiffer ignoring first value of matrix

Summary:
Changelog: [internal]

# Problem

Implementation of `matricesDiffer` was ignoring first element in the matrix, therefore two matrixes that were different were actually evaluated as same and React didn't pass value to native.

# Solution

Take first element in the matrix into account when comparing matrices.

Reviewed By: cpojer

Differential Revision: D20117210

fbshipit-source-id: 84c3b4e580da44bda4fc8bd8669318282ae9aa32
---
 .../differ/__tests__/matricesDiffer-test.js   | 45 +++++++++++++++++++
 Libraries/Utilities/differ/matricesDiffer.js  |  1 +
 2 files changed, 46 insertions(+)
 create mode 100644 Libraries/Utilities/differ/__tests__/matricesDiffer-test.js

diff --git a/Libraries/Utilities/differ/__tests__/matricesDiffer-test.js b/Libraries/Utilities/differ/__tests__/matricesDiffer-test.js
new file mode 100644
index 00000000000..26cc35ce3f5
--- /dev/null
+++ b/Libraries/Utilities/differ/__tests__/matricesDiffer-test.js
@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @emails oncall+react_native
+ */
+
+'use strict';
+
+const matricesDiffer = require('../matricesDiffer');
+
+describe('matricesDiffer', function() {
+  it('diffs matrices with single element', () => {
+    var x = [1];
+    var y = [2];
+    expect(matricesDiffer(x, y)).toBe(true);
+
+    x = [1];
+    y = [1];
+    expect(matricesDiffer(x, y)).toBe(false);
+  });
+
+  it('diffs matrices with different number of elements', () => {
+    var x = [1, 1, 1, 1];
+    var y = [1, 1, 1, 2];
+    expect(matricesDiffer(x, y)).toBe(true);
+  });
+
+  it('diffs matrices with 16 elements', () => {
+    var x = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
+    var y = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
+    expect(matricesDiffer(x, y)).toBe(false);
+
+    x = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
+    y = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1];
+    expect(matricesDiffer(x, y)).toBe(true);
+
+    x = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
+    y = [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1];
+    expect(matricesDiffer(x, y)).toBe(true);
+  });
+});
diff --git a/Libraries/Utilities/differ/matricesDiffer.js b/Libraries/Utilities/differ/matricesDiffer.js
index ade2a5fc3f9..1726ad361e3 100644
--- a/Libraries/Utilities/differ/matricesDiffer.js
+++ b/Libraries/Utilities/differ/matricesDiffer.js
@@ -30,6 +30,7 @@ const matricesDiffer = function(one, two) {
     one[14] !== two[14] ||
     one[5] !== two[5] ||
     one[10] !== two[10] ||
+    one[0] !== two[0] ||
     one[1] !== two[1] ||
     one[2] !== two[2] ||
     one[3] !== two[3] ||