From 479f87e1e008cbf8fcd23cef2eacab2754561ced Mon Sep 17 00:00:00 2001
From: Jose Lorenzo Rodriguez <jose.zap@gmail.com>
Date: Tue, 4 Sep 2018 10:53:47 +0200
Subject: [PATCH] Fixed code for lastN when passing a countable

---
 src/Collection/CollectionTrait.php           |  4 +++-
 tests/TestCase/Collection/CollectionTest.php | 25 +++++++++++++++++---
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/Collection/CollectionTrait.php b/src/Collection/CollectionTrait.php
index e33ddf4ec94..76e10189f42 100644
--- a/src/Collection/CollectionTrait.php
+++ b/src/Collection/CollectionTrait.php
@@ -415,9 +415,11 @@ public function lastN($howMany)
 
         if ($iterator instanceof Countable) {
             $count = count($iterator);
+
             if ($count === 0) {
-                return null;
+                return new Collection([]);
             }
+
             $iterator = new LimitIterator($iterator, max(0, $count - $howMany), $howMany);
 
             return new Collection($iterator);
diff --git a/tests/TestCase/Collection/CollectionTest.php b/tests/TestCase/Collection/CollectionTest.php
index ff58eab4c9b..27b2ef20bfe 100644
--- a/tests/TestCase/Collection/CollectionTest.php
+++ b/tests/TestCase/Collection/CollectionTest.php
@@ -63,6 +63,24 @@ public function checkValues()
     }
 }
 
+class CountableIterator extends \IteratorIterator implements \Countable
+{
+    public function __construct($items)
+    {
+        $f = function () use ($items) {
+            foreach ($items as $e) {
+                yield $e;
+            }
+        };
+        parent::__construct($f());
+    }
+
+    public function count()
+    {
+        return 6;
+    }
+}
+
 /**
  * CollectionTest
  */
@@ -2199,11 +2217,12 @@ public function testLasNtWithOddData($data)
      */
     public function testLasNtWithCountable()
     {
-        $collection = new Collection(new ArrayObject([1, 2, 3, 4, 5]));
-        $result = $collection->lastN(2)->toArray();
+        $collection = new Collection(new CountableIterator(range(0, 5)));
+        $result = $collection->lastN(2)->toList();
         $this->assertEquals([4, 5], $result);
 
-        $result = $collection->lastN(1)->toArray();
+        $collection = new Collection(new CountableIterator(range(0, 5)));
+        $result = $collection->lastN(1)->toList();
         $this->assertEquals([5], $result);
     }