tempestphp
@@ -14,8 +14,6 @@
 use Tempest\Reflection\ClassReflector;
 use Tempest\Reflection\PropertyReflector;
 
-use function Tempest\Mapper\map;
-
 final readonly class ObjectToArrayMapper implements Mapper
 {
     public function __construct(
@@ -30,32 +28,63 @@ public function canMap(mixed $from, mixed $to): bool
 
     public function map(mixed $from, mixed $to): mixed
     {
-        if ($from instanceof JsonSerializable) {
-            return $from->jsonSerialize();
+        $visited = [];
+
+        return $this->mapValue($from, $visited);
+    }
+
+    /**
+     * @param array<int, true> $visited
+     */
+    private function mapValue(mixed $value, array &$visited): mixed
+    {
+        if ($value instanceof JsonSerializable) {
+            return $value->jsonSerialize();
         }
 
-        if (is_object($from)) {
-            $class = new ClassReflector($from);
+        if (! is_object($value)) {
+            return $value;
+        }
 
-            $mappedProperties = [];
+        return $this->mapObject($value, $visited);
+    }
 
-            foreach ($class->getPublicProperties() as $property) {
-                if ($property->hasAttribute(Hidden::class)) {
-                    continue;
-                }
+    /**
+     * @param array<int, true> $visited
+     */
+    private function mapObject(object $object, array &$visited): mixed
+    {
+        $objectId = spl_object_id($object);
 
-                $propertyName = $this->resolvePropertyName($property);
-                $propertyValue = $this->resolvePropertyValue($property, $from);
-                $mappedProperties[$propertyName] = $propertyValue;
+        if (isset($visited[$objectId])) {
+            return $object;
+        }
+
+        $visited[$objectId] = true;
+
+        $class = new ClassReflector($object);
+
+        $mappedProperties = [];
+
+        foreach ($class->getPublicProperties() as $property) {
+            if ($property->hasAttribute(Hidden::class)) {
+                continue;
             }
-        } else {
-            $mappedProperties = $from;
+
+            $propertyName = $this->resolvePropertyName($property);
+            $propertyValue = $this->resolvePropertyValue($property, $object, $visited);
+            $mappedProperties[$propertyName] = $propertyValue;
         }
 
+        unset($visited[$objectId]);
+
         return $mappedProperties;
     }
 
-    private function resolvePropertyValue(PropertyReflector $property, object $object): mixed
+    /**
+     * @param array<int, true> $visited
+     */
+    private function resolvePropertyValue(PropertyReflector $property, object $object, array &$visited): mixed
     {
         if (! $property->isInitialized($object)) {
             return null;
@@ -69,7 +98,7 @@ private function resolvePropertyValue(PropertyReflector $property, object $objec
                     continue;
                 }
 
-                $propertyValue[$key] = map($value)->toArray();
+                $propertyValue[$key] = $this->mapValue($value, $visited);
             }
 
             return $propertyValue;
@@ -79,6 +108,10 @@ private function resolvePropertyValue(PropertyReflector $property, object $objec
             return $serializer->serialize($propertyValue);
         }
 
+        if ($propertyValue !== null && is_object($propertyValue)) {
+            return $this->mapValue($propertyValue, $visited);
+        }
+
         return $propertyValue;
     }
 

@@ -4,9 +4,12 @@
 
 namespace Tempest\Mapper\Serializers;
 
+use Tempest\Mapper\ConfigurableSerializer;
+use Tempest\Mapper\Context;
 use Tempest\Mapper\DynamicSerializer;
 use Tempest\Mapper\Exceptions\ValueCouldNotBeSerialized;
 use Tempest\Mapper\Mappers\ObjectToArrayMapper;
+use Tempest\Mapper\MappingContext;
 use Tempest\Mapper\Serializer;
 use Tempest\Reflection\PropertyReflector;
 use Tempest\Reflection\TypeReflector;
@@ -15,8 +18,16 @@
 use function Tempest\Mapper\map;
 
 #[Priority(Priority::HIGHEST)]
-final class ArrayOfObjectsSerializer implements Serializer, DynamicSerializer
+final class ArrayOfObjectsSerializer implements Serializer, DynamicSerializer, ConfigurableSerializer
 {
+    private readonly Context $context;
+
+    public function __construct(
+        ?Context $context = null,
+    ) {
+        $this->context = $context ?? MappingContext::default();
+    }
+
     public static function accepts(PropertyReflector|TypeReflector $input): bool
     {
         if ($input instanceof TypeReflector) {
@@ -26,6 +37,11 @@ public static function accepts(PropertyReflector|TypeReflector $input): bool
         return $input->getIterableType() instanceof TypeReflector;
     }
 
+    public static function configure(PropertyReflector|TypeReflector|string $input, Context $context): Serializer
+    {
+        return new self($context);
+    }
+
     public function serialize(mixed $input): array
     {
         if (! is_array($input)) {
@@ -35,7 +51,10 @@ public function serialize(mixed $input): array
         $values = [];
 
         foreach ($input as $key => $object) {
-            $values[$key] = map($object)->with(ObjectToArrayMapper::class)->do();
+            $values[$key] = map($object)
+                ->in($this->context)
+                ->with(ObjectToArrayMapper::class)
+                ->do();
         }
 
         return $values;

diff --git a/tests/Integration/Mapper/Fixtures/NestedObjectWithDate.php b/tests/Integration/Mapper/Fixtures/NestedObjectWithDate.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Tempest\Integration\Mapper\Fixtures;
+
+use Tempest\DateTime\DateTime;
+use Tempest\DateTime\FormatPattern;
+use Tempest\Validation\Rules\HasDateTimeFormat;
+
+final readonly class NestedObjectWithDate
+{
+    public function __construct(
+        #[HasDateTimeFormat(FormatPattern::ISO8601)]
+        public DateTime $createdAt,
+    ) {}
+}
diff --git a/tests/Integration/Mapper/Fixtures/ObjectWithNestedObjectAndDate.php b/tests/Integration/Mapper/Fixtures/ObjectWithNestedObjectAndDate.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Tempest\Integration\Mapper\Fixtures;
+
+use Tempest\DateTime\DateTime;
+use Tempest\DateTime\FormatPattern;
+use Tempest\Validation\Rules\HasDateTimeFormat;
+
+final readonly class ObjectWithNestedObjectAndDate
+{
+    public function __construct(
+        #[HasDateTimeFormat(FormatPattern::ISO8601)]
+        public DateTime $createdAt,
+        public NestedObjectWithDate $child,
+        /** @var \Tests\Tempest\Integration\Mapper\Fixtures\NestedObjectWithDate[] */
+        public array $children,
+    ) {}
+}
diff --git a/tests/Integration/Mapper/Mappers/ObjectToArrayMapperTest.php b/tests/Integration/Mapper/Mappers/ObjectToArrayMapperTest.php
@@ -4,12 +4,21 @@
 
 namespace Tests\Tempest\Integration\Mapper\Mappers;
 
+use PHPUnit\Framework\Attributes\RequiresPhpExtension;
 use PHPUnit\Framework\Attributes\Test;
+use RuntimeException;
+use Tempest\DateTime\DateTime;
+use Tempest\Mapper\Mapper;
+use Tempest\Mapper\MapperConfig;
+use Tempest\Support\Json\Exception\JsonCouldNotBeEncoded;
 use Tests\Tempest\Integration\FrameworkIntegrationTestCase;
+use Tests\Tempest\Integration\Mapper\Fixtures\NestedObjectWithDate;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectA;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithJsonSerialize;
+use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithNestedObjectAndDate;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithNullableProperties;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithScalarValues;
+use Tests\Tempest\Integration\Mapper\Fixtures\ParentObject;
 
 use function Tempest\Mapper\map;
 
@@ -69,4 +78,110 @@ public function object_with_scalar_values_to_array(): void
             $array,
         );
     }
+
+    #[Test]
+    public function object_with_single_nested_object_to_array(): void
+    {
+        $date = DateTime::parse('2026-08-19T12:34:56+00:00');
+
+        $array = map(new ObjectWithNestedObjectAndDate(
+            createdAt: $date,
+            child: new NestedObjectWithDate($date),
+            children: [new NestedObjectWithDate($date)],
+        ))->toArray();
+
+        $this->assertSame(
+            [
+                'createdAt' => '2026-08-19T12:34:56.000Z',
+                'child' => [
+                    'createdAt' => '2026-08-19T12:34:56.000Z',
+                ],
+                'children' => [
+                    ['createdAt' => '2026-08-19T12:34:56.000Z'],
+                ],
+            ],
+            $array,
+        );
+    }
+
+    #[Test]
+    #[RequiresPhpExtension('pcntl')]
+    public function cyclic_nested_objects_fail_instead_of_hanging(): void
+    {
+        $parent = map([
+            'name' => 'parent',
+            'child' => ['name' => 'child'],
+        ])->to(ParentObject::class);
+        $this->assertInstanceOf(ParentObject::class, $parent);
+
+        pcntl_async_signals(true);
+        pcntl_signal(SIGALRM, static function (): never {
+            throw new RuntimeException('Serialization did not terminate');
+        });
+        pcntl_alarm(2);
+
+        try {
+            $this->expectException(JsonCouldNotBeEncoded::class);
+
+            map($parent)->toJson();
+        } finally {
+            pcntl_alarm(0);
+            pcntl_signal(SIGALRM, SIG_DFL);
+        }
+    }
+
+    #[Test]
+    public function nested_objects_do_not_resolve_unused_mappers(): void
+    {
+        map(new ObjectA('a', 'b'))->toArray();
+
+        $this->container
+            ->get(MapperConfig::class)
+            ->addMapper(MapperResolutionProbe::class);
+
+        MapperResolutionProbe::$constructions = 0;
+
+        map(new ObjectWithMapperResolutionChildren([
+            new MapperResolutionChild('a'),
+            new MapperResolutionChild('b'),
+            new MapperResolutionChild('c'),
+        ]))->toArray();
+
+        $this->assertSame(0, MapperResolutionProbe::$constructions);
+    }
+}
+
+final readonly class ObjectWithMapperResolutionChildren
+{
+    public function __construct(
+        /** @var \Tests\Tempest\Integration\Mapper\Mappers\MapperResolutionChild[] */
+        public array $children,
+    ) {}
+}
+
+final readonly class MapperResolutionChild
+{
+    public function __construct(
+        public string $name,
+    ) {}
+}
+
+final class MapperResolutionProbe implements Mapper
+{
+    public static int $constructions = 0;
+
+    public function __construct()
+    {
+        self::$constructions++;
+    }
+
+    public function canMap(mixed $from, mixed $to): bool
+    {
+        return false;
+    }
+
+    public function map(mixed $from, mixed $to): mixed
+    {
+        return $from;
+    }
 }
diff --git a/tests/Integration/Mapper/Mappers/ObjectToJsonMapperTest.php b/tests/Integration/Mapper/Mappers/ObjectToJsonMapperTest.php
@@ -5,8 +5,11 @@
 namespace Tests\Tempest\Integration\Mapper\Mappers;
 
 use PHPUnit\Framework\Attributes\Test;
+use Tempest\DateTime\DateTime;
 use Tests\Tempest\Integration\FrameworkIntegrationTestCase;
+use Tests\Tempest\Integration\Mapper\Fixtures\NestedObjectWithDate;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectA;
+use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithNestedObjectAndDate;
 use Tests\Tempest\Integration\Mapper\Fixtures\ObjectWithScalarValues;
 
 use function Tempest\Mapper\map;
@@ -42,4 +45,29 @@ public function object_with_scalar_values_to_json(): void
             json_decode($json, associative: true, flags: JSON_THROW_ON_ERROR),
         );
     }
+
+    #[Test]
+    public function object_with_single_nested_object_to_json(): void
+    {
+        $date = DateTime::parse('2026-08-19T12:34:56+00:00');
+
+        $json = map(new ObjectWithNestedObjectAndDate(
+            createdAt: $date,
+            child: new NestedObjectWithDate($date),
+            children: [new NestedObjectWithDate($date)],
+        ))->toJson();
+
+        $this->assertSame(
+            [
+                'createdAt' => '2026-08-19T12:34:56.000Z',
+                'child' => [
+                    'createdAt' => '2026-08-19T12:34:56.000Z',
+                ],
+                'children' => [
+                    ['createdAt' => '2026-08-19T12:34:56.000Z'],
+                ],
+            ],
+            json_decode($json, associative: true, flags: JSON_THROW_ON_ERROR),
+        );
+    }
 }