From 882d84f1e66776695eed4e784bb8a66507912f5f Mon Sep 17 00:00:00 2001
From: jdalton <john.david.dalton@gmail.com>
Date: Mon, 18 May 2015 07:29:35 -0700
Subject: [PATCH] Ensure `_.merge` skips `undefined` values if a destination
 value exists.

---
 lodash.src.js |  2 +-
 test/test.js  | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/lodash.src.js b/lodash.src.js
index b806d9bd3..5ef870596 100644
--- a/lodash.src.js
+++ b/lodash.src.js
@@ -2534,7 +2534,7 @@
           if (isCommon) {
             result = srcValue;
           }
-          if ((isSrcArr || result !== undefined) &&
+          if ((result !== undefined || (isSrcArr && !(key in object))) &&
               (isCommon || (result === result ? (result !== value) : (value === value)))) {
             object[key] = result;
           }
diff --git a/test/test.js b/test/test.js
index 94a8bf40b..f48e03240 100644
--- a/test/test.js
+++ b/test/test.js
@@ -10681,6 +10681,23 @@
       deepEqual(actual, expected);
     });
 
+    test('should skip `undefined` values in arrays if a destination value exists', 2, function() {
+      var array = Array(3);
+      array[0] = 1;
+      array[2] = 3;
+
+      var actual = _.merge([4, 5, 6], array),
+          expected = [1, 5, 3];
+
+      deepEqual(actual, expected);
+
+      array = [1, , 3];
+      array[1] = undefined;
+
+      actual = _.merge([4, 5, 6], array);
+      deepEqual(actual, expected);
+    });
+
     test('should merge `arguments` objects', 3, function() {
       var object1 = { 'value': args },
           object2 = { 'value': { '3': 4 } },