Enforce 1 being the minimal chunk size

#1919

test/arrays.js

@@ -542,12 +542,12 @@
   test('chunk', function() {
     deepEqual(_.chunk([], 2), [], 'chunk for empty array returns an empty array');
 
-    deepEqual(_.chunk([1, 2, 3], 0), [1, 2, 3], 'chunk into parts of 0 elements returns original array');
+    deepEqual(_.chunk([1, 2, 3], 0), [], 'chunk into parts of 0 elements returns empty array');
+    deepEqual(_.chunk([1, 2, 3], -1), [], 'chunk into parts of negative amount of elements returns an empty array');
+    deepEqual(_.chunk([1, 2, 3]), [], 'defaults to empty array (chunk size 0)');
+    deepEqual(_.chunk([1, 2, 3], {}), [], 'nonsense defaults to empty array (chunk size 0)');
 
-    deepEqual(_.chunk([1, 2, 3], 1), [1, 2, 3], 'chunk into parts of 1 elements returns original array');
-    deepEqual(_.chunk([1, 2, 3]), [1, 2, 3], 'chunk into parts of 1 elements is default value and returns original array');
-
-    deepEqual(_.chunk([1, 2, 3], -1), [1, 2, 3], 'chunk into parts of negative amount of elements returns an empty array');
+    deepEqual(_.chunk([1, 2, 3], 1), [[1], [2], [3]], 'chunk into parts of 1 elements returns original array');
 
     deepEqual(_.chunk([1, 2, 3], 3), [[1, 2, 3]], 'chunk into parts of current array length elements returns the original array');
     deepEqual(_.chunk([1, 2, 3], 5), [[1, 2, 3]], 'chunk into parts of more then current array length elements returns the original array');

underscore.js

@@ -699,15 +699,13 @@
   // Split an **array** into several arrays containing **count** or less elements
   // of initial array
   _.chunk = function(array, count) {
-    count = +count || 1;
-    if (count <= 1) return slice.call(array);
+    if (!(count >= 1)) return [];
 
     var result = [];
     var i = 0, length = array.length;
     while (i < length) {
       result.push(slice.call(array, i, i += count));
     }
-
     return result;
   };