fix(mapper): properly serialize nullable properties in objects (#1107)

Author: olml89

src/Tempest/Mapper/src/Mappers/ObjectToArrayMapper.php

@@ -45,7 +45,7 @@ private function resolvePropertyValue(PropertyReflector $property, object $objec
     {
         $propertyValue = $property->getValue($object);
 
-        if (($serializer = $this->serializerFactory->forProperty($property)) !== null) {
+        if ($propertyValue !== null && ($serializer = $this->serializerFactory->forProperty($property)) !== null) {
             return $serializer->serialize($propertyValue);
         }
 

tests/Integration/Mapper/Fixtures/ObjectWithNullableProperties.php

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Tempest\Integration\Mapper\Fixtures;
+
+use DateTimeImmutable;
+use Tempest\Mapper\Strict;
+
+#[Strict]
+final class ObjectWithNullableProperties
+{
+    public function __construct(
+        public string $a,
+        public float $b,
+        public ?DateTimeImmutable $c,
+    ) {}
+}

tests/Integration/Mapper/Mappers/ObjectToArrayMapperTestCase.php

@@ -7,10 +7,12 @@
 use Tests\Tempest\Integration\FrameworkIntegrationTestCase;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectA;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithJsonSerialize;
+use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithNullableProperties;
 
 use function Tempest\map;
 
 /**
+ *
  * @internal
  */
 final class ObjectToArrayMapperTestCase extends FrameworkIntegrationTestCase
@@ -28,4 +30,19 @@ public function test_custom_to_array(): void
 
         $this->assertSame(['c' => 'a', 'd' => 'b'], $array);
     }
+
+    public function test_object_with_nullable_properties_to_array(): void
+    {
+        $object = new ObjectWithNullableProperties(a: 'a', b: 3.1416, c: null);
+        $array = map($object)->toArray();
+
+        $this->assertSame(
+            [
+                'a' => 'a',
+                'b' => '3.1416',
+                'c' => null,
+            ],
+            $array,
+        );
+    }
 }