[stable28] fix xml ocs response for serializable objects

lib/private/AppFramework/OCS/BaseResponse.php

@@ -159,6 +159,10 @@ protected function toXML(array $array, \XMLWriter $writer): void {
 				$writer->startElement($k);
 				$this->toXML($v, $writer);
 				$writer->endElement();
+			} elseif ($v instanceof \JsonSerializable) {
+				$writer->startElement($k);
+				$this->toXML($v->jsonSerialize(), $writer);
+				$writer->endElement();
 			} else {
 				$writer->writeElement($k, $v);
 			}

tests/lib/AppFramework/OCS/BaseResponseTest.php

@@ -28,6 +28,17 @@
 
 use OC\AppFramework\OCS\BaseResponse;
 
+class ArrayValue implements \JsonSerializable {
+	private $array;
+	public function __construct(array $array) {
+		$this->array = $array;
+	}
+
+	public function jsonSerialize(): mixed {
+		return $this->array;
+	}
+}
+
 class BaseResponseTest extends \Test\TestCase {
 	public function testToXml(): void {
 		/** @var BaseResponse $response */
@@ -56,4 +67,32 @@ public function testToXml(): void {
 			$writer->outputMemory(true)
 		);
 	}
+
+	public function testToXmlJsonSerializable(): void {
+		/** @var BaseResponse $response */
+		$response = $this->createMock(BaseResponse::class);
+
+		$writer = new \XMLWriter();
+		$writer->openMemory();
+		$writer->setIndent(false);
+		$writer->startDocument();
+
+		$data = [
+			'hello' => 'hello',
+			'information' => new ArrayValue([
+				'@test' => 'some data',
+				'someElement' => 'withAttribute',
+			]),
+			'value without key',
+			'object' => new \stdClass(),
+		];
+
+		$this->invokePrivate($response, 'toXml', [$data, $writer]);
+		$writer->endDocument();
+
+		$this->assertEquals(
+			"<?xml version=\"1.0\"?>\n<hello>hello</hello><information test=\"some data\"><someElement>withAttribute</someElement></information><element>value without key</element><object/>\n",
+			$writer->outputMemory(true)
+		);
+	}
 }