don't read current key and value when end of iterator is reached

src/Runtime/LoopIterator.php

@@ -67,7 +67,11 @@ final class LoopIterator implements \Iterator
         } else {
             $this->seq->next();
         }
-        $this->current = ['valid' => $this->seq->valid(), 'key' => $this->seq->key(), 'value' => $this->seq->current()];
+        if ($this->seq->valid()) {
+            $this->current = ['valid' => $this->seq->valid(), 'key' => $this->seq->key(), 'value' => $this->seq->current()];
+        } else {
+            $this->current = ['valid' => false, 'key' => null, 'value' => null];
+        }
         ++$this->index0;
     }
 

tests/Runtime/LoopIteratorTest.php

@@ -0,0 +1,111 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Tests\Runtime;
+
+use PHPUnit\Framework\TestCase;
+use Twig\Runtime\LoopIterator;
+
+class LoopIteratorTest extends TestCase
+{
+    /**
+     * @dataProvider provideIterablesForNext
+     */
+    public function testNextWhenValid(iterable $iterable)
+    {
+        $iterator = new LoopIterator($iterable);
+        $iterator->next();
+
+        $this->assertTrue($iterator->valid());
+        $this->assertSame(1, $iterator->key());
+        $this->assertSame('bar', $iterator->current());
+    }
+
+    /**
+     * @dataProvider provideIterablesForNext
+     */
+    public function testNextWhenNotValid(iterable $iterable)
+    {
+        $iterator = new LoopIterator($iterable);
+        $iterator->next();
+        $iterator->next();
+
+        $this->assertFalse($iterator->valid());
+        $this->assertNull($iterator->key());
+        $this->assertNull($iterator->current());
+    }
+
+    public function provideIterablesForNext()
+    {
+        yield [['foo', 'bar']];
+        yield [new \ArrayIterator(['foo', 'bar'])];
+        yield [new TypedArrayIterator(['foo', 'bar'])];
+    }
+
+    /**
+     * @dataProvider provideIterablesForRewind
+     */
+    public function testRewind(iterable $iterable)
+    {
+        $iterator = new LoopIterator($iterable);
+        $iterator->next();
+
+        $this->assertTrue($iterator->valid());
+        $this->assertSame(1, $iterator->key());
+        $this->assertSame('bar', $iterator->current());
+
+        $iterator->rewind();
+
+        $this->assertTrue($iterator->valid());
+        $this->assertSame(0, $iterator->key());
+        $this->assertSame('foo', $iterator->current());
+    }
+
+    public function provideIterablesForRewind()
+    {
+        yield [['foo', 'bar']];
+        yield [new \ArrayIterator(['foo', 'bar'])];
+        yield [new TypedArrayIterator(['foo', 'bar'])];
+    }
+}
+
+class TypedArrayIterator implements \Iterator
+{
+    public function __construct(
+        private array $values,
+    ) {
+    }
+
+    public function current(): string
+    {
+        return current($this->values);
+    }
+
+    public function next(): void
+    {
+        next($this->values);
+    }
+
+    public function key(): int
+    {
+        return key($this->values);
+    }
+
+    public function valid(): bool
+    {
+        return null !== key($this->values);
+    }
+
+    public function rewind(): void
+    {
+        reset($this->values);
+    }
+}