Fix marshalling/unmarshalling of nullable object properties (#334)

src/Internal/Marshaller/Type/ObjectType.php

@@ -55,7 +55,13 @@ public static function makeRule(\ReflectionProperty $property): ?MarshallingRule
             return null;
         }
 
-        return new MarshallingRule($property->getName(), self::class, $type->getName());
+        return $type->allowsNull()
+            ? new MarshallingRule(
+                $property->getName(),
+                NullableType::class,
+                new MarshallingRule(type: self::class, of: $type->getName()),
+            )
+            : new MarshallingRule($property->getName(), self::class, $type->getName());
     }
 
     /**

tests/Unit/DTO/Type/ObjectType/ObjectTypeTestCase.php

@@ -18,6 +18,7 @@
 use Temporal\Tests\Unit\DTO\Type\ObjectType\Stub\Nested2;
 use Temporal\Tests\Unit\DTO\Type\ObjectType\Stub\Nested3;
 use Temporal\Tests\Unit\DTO\Type\ObjectType\Stub\NestedParent;
+use Temporal\Tests\Unit\DTO\Type\ObjectType\Stub\NullableProperty;
 use Temporal\Tests\Unit\DTO\Type\ObjectType\Stub\ParentDto;
 use Temporal\Tests\Unit\DTO\DTOMarshallingTestCase;
 use Temporal\Tests\Unit\DTO\Type\ObjectType\Stub\ReadonlyProperty;
@@ -60,6 +61,24 @@ public function testReadonlyMarshal(): void
         $this->assertEquals(['child' => ['foo' => 'foo']], $result);
     }
 
+    public function testNullableObjectMarshal(): void
+    {
+        $dto = new NullableProperty(null);
+
+        $result = $this->marshal($dto);
+
+        $this->assertEquals(['child' => null], $result);
+    }
+
+    public function testNullableObjectUnmarshal(): void
+    {
+        $dto = $this->unmarshal([
+            'child' => null,
+        ], (new ReflectionClass(NullableProperty::class))->newInstanceWithoutConstructor());
+
+        self::assertEquals(new NullableProperty(null), $dto);
+    }
+
     /**
      * @requires PHP >= 8.1
      */

tests/Unit/DTO/Type/ObjectType/Stub/NullableProperty.php

@@ -0,0 +1,20 @@
+<?php
+
+/**
+ * This file is part of Temporal package.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Temporal\Tests\Unit\DTO\Type\ObjectType\Stub;
+
+final class NullableProperty
+{
+    public function __construct(
+        public ?ChildDto $child,
+    ) {
+    }
+}