bug #3104 Fix the "empty" test on Traversable instances (fabpot)

This PR was merged into the 1.x branch.

Discussion
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Fix the "empty" test on Traversable instances

closes #3101

Commits
-------

b202fe38 fixed the "empty" test on Traversable instances

CHANGELOG

@@ -1,5 +1,6 @@
 * 1.42.3 (2019-XX-XX)
 
+ * fixed the "empty" test on Traversable instances
  * fixed cache when opcache is installed but disabled
 
 * 1.42.2 (2019-06-18)

src/Extension/CoreExtension.php

@@ -1507,6 +1507,10 @@ function twig_test_empty($value)
         return 0 == \count($value);
     }
 
+    if ($value instanceof \Traversable) {
+        return !iterator_count($value);
+    }
+
     if (\is_object($value) && method_exists($value, '__toString')) {
         return '' === (string) $value;
     }

tests/Fixtures/tests/empty.test

@@ -15,6 +15,10 @@
 {{ tostring_not_empty is empty ? 'ko' : 'ok' }}
 {{ markup_empty is empty ? 'ok' : 'ko' }}
 {{ markup_not_empty is empty ? 'ko' : 'ok' }}
+{{ iterator is empty ? 'ko' : 'ok' }}
+{{ empty_iterator is empty ? 'ok' : 'ko' }}
+{{ callback_iterator is empty ? 'ko' : 'ok' }}
+{{ empty_callback_iterator is empty ? 'ok' : 'ko' }}
 --DATA--
 return [
     'string_empty' => '', 'string_zero' => '0',
@@ -24,6 +28,10 @@ return [
     'countable_empty' => new \Twig\Tests\CountableStub([]), 'countable_not_empty' => new \Twig\Tests\CountableStub([1, 2]),
     'tostring_empty' => new \Twig\Tests\ToStringStub(''), 'tostring_not_empty' => new \Twig\Tests\ToStringStub('0' /* edge case of using "0" as the string */),
     'markup_empty' => new \Twig\Markup('', 'UTF-8'), 'markup_not_empty' => new \Twig\Markup('test', 'UTF-8'),
+    'iterator' => $iter = new \ArrayIterator(['bar', 'foo']),
+    'empty_iterator' => new \ArrayIterator(),
+    'callback_iterator' => new \CallbackFilterIterator($iter, function ($el) { return true; }),
+    'empty_callback_iterator' => new \CallbackFilterIterator($iter, function ($el) { return false; }),
 ]
 --EXPECT--
 ok
@@ -40,3 +48,7 @@ ok
 ok
 ok
 ok
+ok
+ok
+ok
+ok