Use a lazyintertor to close files descriptors when no longer used

src/Symfony/Component/Finder/Finder.php

@@ -20,6 +20,7 @@ use Symfony\Component\Finder\Iterator\DepthRangeFilterIterator;
 use Symfony\Component\Finder\Iterator\ExcludeDirectoryFilterIterator;
 use Symfony\Component\Finder\Iterator\FilecontentFilterIterator;
 use Symfony\Component\Finder\Iterator\FilenameFilterIterator;
+use Symfony\Component\Finder\Iterator\LazyIterator;
 use Symfony\Component\Finder\Iterator\SizeRangeFilterIterator;
 use Symfony\Component\Finder\Iterator\SortableIterator;
 
@@ -635,7 +636,9 @@ class Finder implements \IteratorAggregate, \Countable
 
         $iterator = new \AppendIterator();
         foreach ($this->dirs as $dir) {
-            $iterator->append($this->searchInDirectory($dir));
+            $iterator->append(new \IteratorIterator(new LazyIterator(function () use ($dir) {
+                return $this->searchInDirectory($dir);
+            })));
         }
 
         foreach ($this->iterators as $it) {

src/Symfony/Component/Finder/Iterator/LazyIterator.php

@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Finder\Iterator;
+
+/**
+ * @author Jérémy Derussé <jeremy@derusse.com>
+ */
+class LazyIterator implements \IteratorAggregate
+{
+    private $iteratorFactory;
+
+    public function __construct(callable $iteratorFactory)
+    {
+        $this->iteratorFactory = $iteratorFactory;
+    }
+
+    public function getIterator()
+    {
+        yield from ($this->iteratorFactory)();
+    }
+}

src/Symfony/Component/Finder/Tests/Iterator/LazyIteratorTest.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Finder\Tests\Iterator;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Finder\Iterator\LazyIterator;
+
+class LazyIteratorTest extends TestCase
+{
+    public function testLazy()
+    {
+        new LazyIterator(function () {
+            $this->markTestFailed('lazyIterator should not be called');
+        });
+
+        $this->expectNotToPerformAssertions();
+    }
+
+    public function testDelegate()
+    {
+        $iterator = new LazyIterator(function () {
+            return new Iterator(['foo', 'bar']);
+        });
+
+        $this->assertCount(2, $iterator);
+    }
+
+    public function testInnerDestructedAtTheEnd()
+    {
+        $count = 0;
+        $iterator = new LazyIterator(function () use (&$count) {
+            ++$count;
+
+            return new Iterator(['foo', 'bar']);
+        });
+
+        foreach ($iterator as $x) {
+        }
+        $this->assertSame(1, $count);
+        foreach ($iterator as $x) {
+        }
+        $this->assertSame(2, $count);
+    }
+}