Fix: prevent "Cannot traverse an already closed generator" error by materializing Traversable input

santysisi · santysisi · commit c6d056deafb0 · 2025-04-23T18:58:26.000-03:00
diff --git a/src/Symfony/Component/Serializer/Encoder/CsvEncoder.php b/src/Symfony/Component/Serializer/Encoder/CsvEncoder.php
@@ -65,6 +65,12 @@ public function encode(mixed $data, string $format, array $context = []): string
         } elseif (empty($data)) {
             $data = [[]];
         } else {
+            // TODO: Remove this check once PHP 8.2+ is the minimum supported version.
+            // In PHP 8.2, iterator_to_array() accepts iterable, so this instanceof check becomes unnecessary.
+            if ($data instanceof \Traversable) {
+                // Generators can only be iterated once — convert to array to allow multiple traversals
+                $data = iterator_to_array($data);
+            }
             // Sequential arrays of arrays are considered as collections
             $i = 0;
             foreach ($data as $key => $value) {
diff --git a/src/Symfony/Component/Serializer/Tests/Encoder/CsvEncoderTest.php b/src/Symfony/Component/Serializer/Tests/Encoder/CsvEncoderTest.php
@@ -710,4 +710,16 @@ public function testEndOfLinePassedInConstructor()
         $encoder = new CsvEncoder([CsvEncoder::END_OF_LINE => "\r\n"]);
         $this->assertSame("foo,bar\r\nhello,test\r\n", $encoder->encode($value, 'csv'));
     }
+
+    public function testEncodeWithGenerator()
+    {
+        $this->assertSame("0\n1\n2\n3\n4\n5\n", $this->encoder->encode($this->getLineIterator(), CsvEncoder::FORMAT));
+    }
+
+    private function getLineIterator(): \Generator
+    {
+        for ($i = 1; $i <= 5; ++$i) {
+            yield [(string) $i];
+        }
+    }
 }
