Ensure _.merge correctly coerces objects to arrays. [closes #1061]

lodash.src.js

@@ -2581,7 +2581,7 @@
         if (isLength(srcValue.length) && (isArray(srcValue) || isTypedArray(srcValue))) {
           result = isArray(value)
             ? value
-            : (value ? arrayCopy(value) : []);
+            : ((value && value.length) ? arrayCopy(value) : []);
         }
         else if (isPlainObject(srcValue) || isArguments(srcValue)) {
           result = isArguments(value)

test/test.js

@@ -9995,8 +9995,10 @@
     });
 
     test('should work with four arguments', 1, function() {
-      var expected = { 'a': 4 };
+      var expected = { 'a': 4 },
-      deepEqual(_.merge({ 'a': 1 }, { 'a': 2 }, { 'a': 3 }, expected), expected);
+          actual = _.merge({ 'a': 1 }, { 'a': 2 }, { 'a': 3 }, expected);
+
+      deepEqual(actual, expected);
     });
 
     test('should assign `null` values', 1, function() {
@@ -10009,7 +10011,7 @@
       deepEqual(actual, { 'a': 1 });
     });
 
-    test('should not not error on DOM elements', 1, function() {
+    test('should not error on DOM elements', 1, function() {
       var object1 = { 'el': document && document.createElement('div') },
           object2 = { 'el': document && document.createElement('div') },
           pairs = [[{}, object1], [object1, object2]],
@@ -10038,6 +10040,16 @@
       deepEqual(actual, expected);
     });
 
+    test('should convert values to an array when merging with arrays of `source`', 2, function() {
+      var object = { 'a': { '1': 'y', 'b': 'z', 'length': 2 } },
+          actual = _.merge(object, { 'a': ['x'] });
+
+      deepEqual(actual, { 'a': ['x', 'y'] });
+
+      actual = _.merge({ 'a': {} }, { 'a': [] });
+      deepEqual(actual, { 'a': [] });
+    });
+
     test('should work with a function `object` value', 2, function() {
       function Foo() {}