Be able to count on iterator

doc/filters/length.rst

@@ -14,6 +14,8 @@ return value of the ``count()`` method.
 For objects that implement the ``__toString()`` magic method (and not ``Countable``),
 it will return the length of the string provided by that method.
 
+For objects that implement the ``IteratorAggregate`` interface, ``length`` will use the return value of the ``iterator_count()`` method.
+
 .. code-block:: jinja
 
     {% if users|length > 10 %}

lib/Twig/Extension/Core.php

@@ -1270,6 +1270,10 @@ if (function_exists('mb_get_info')) {
         if ($thing instanceof \Countable || is_array($thing)) {
             return count($thing);
         }
+        
+        if ($thing instanceof \IteratorAggregate) {
+            return iterator_count($thing);
+        }
 
         return 1;
     }
@@ -1369,6 +1373,10 @@ else {
         if ($thing instanceof \Countable || is_array($thing)) {
             return count($thing);
         }
+        
+        if ($thing instanceof \IteratorAggregate) {
+            return iterator_count($thing);
+        }
 
         return 1;
     }

test/Twig/Tests/Fixtures/filters/length.test

@@ -6,6 +6,7 @@
 {{ number|length }}
 {{ to_string_able|length }}
 {{ countable|length }}
+{{ iterator_aggregate|length }}
 {{ null|length }}
 {{ magic|length }}
 {{ non_countable|length }}
@@ -16,6 +17,7 @@ return array(
     'number' => 1000,
     'to_string_able' => new ToStringStub('foobar'),
     'countable' => new CountableStub(42),       /* also asserts we do *not* call __toString() */
+    'iterator_aggregate' => new IteratorAggregateStub(array('a', 'b', 'c')),   /* also asserts we do *not* call __toString() */
     'null'          => null,
     'magic'         => new MagicCallStub(),     /* used to assert we do *not* call __call */
     'non_countable' => new \StdClass(),
@@ -26,6 +28,7 @@ return array(
 4
 6
 42
+3
 0
 1
 1

test/Twig/Tests/IntegrationTest.php

@@ -307,3 +307,21 @@ class CountableStub implements \Countable
         throw new Exception('__toString shall not be called on \Countables');
     }
 }
+
+/**
+ * This class is used in tests for the length filter
+ */
+class IteratorAggregateStub implements \IteratorAggregate
+{
+    private $data;
+
+    public function __construct(array $data)
+    {
+        $this->data = $data;
+    }
+
+    public function getIterator()
+    {
+        return new ArrayIterator($this->data);
+    }
+}