feat(serializer): denormalize into the declared collection class

src/Serializer/AbstractItemNormalizer.php

@@ -28,6 +28,7 @@
 use ApiPlatform\Metadata\UrlGeneratorInterface;
 use ApiPlatform\Metadata\Util\ClassInfoTrait;
 use ApiPlatform\Metadata\Util\CloneTrait;
+use Symfony\Bridge\Doctrine\Serializer\Normalizer\CollectionDenormalizer;
 use Symfony\Component\PropertyAccess\Exception\InvalidArgumentException as PropertyAccessInvalidArgumentException;
 use Symfony\Component\PropertyAccess\Exception\InvalidTypeException;
 use Symfony\Component\PropertyAccess\Exception\NoSuchPropertyException;
@@ -1110,6 +1111,19 @@ private function createAndValidateAttributeValue(string $attribute, mixed $value
                 unset($context['resource_class'], $context['uri_variables']);
 
                 try {
+                    // When the collection is declared with a class, such as a Doctrine collection,
+                    // ask the Serializer to build that class and pass the element and key types
+                    // through the context, the same way the core Serializer does. The class is
+                    // checked so older Symfony versions, which cannot build the collection, keep
+                    // the array type. A plain array or iterable keeps the "Foo[]" type too.
+                    $collectionClass = self::getCollectionContainerClass($t);
+                    if (null !== $collectionClass && class_exists(CollectionDenormalizer::class)) {
+                        $context['value_type'] = $unwrappedCollectionValueType;
+                        $context['key_type'] = $t->getCollectionKeyType();
+
+                        return $this->serializer->denormalize($value, $collectionClass, $format, $context);
+                    }
+
                     return $this->serializer->denormalize($value, $className.'[]', $format, $context);
                 } catch (NotNormalizableValueException $e) {
                     // union/intersect types: try the next type, if not valid, an exception will be thrown at the end
@@ -1272,6 +1286,20 @@ private function createAndValidateAttributeValue(string $attribute, mixed $value
         return $value;
     }
 
+    /**
+     * Returns the class of the container of a collection type, or null when the container is a plain array or iterable.
+     */
+    private static function getCollectionContainerClass(CollectionType $type): ?string
+    {
+        $containerType = $type->getWrappedType();
+
+        while ($containerType instanceof WrappingTypeInterface) {
+            $containerType = $containerType->getWrappedType();
+        }
+
+        return $containerType instanceof ObjectType ? $containerType->getClassName() : null;
+    }
+
     /**
      * Sets a value of the object using the PropertyAccess component.
      */

src/Serializer/Tests/AbstractItemNormalizerTest.php

@@ -50,6 +50,7 @@
 use PHPUnit\Framework\TestCase;
 use Prophecy\Argument;
 use Prophecy\PhpUnit\ProphecyTrait;
+use Symfony\Bridge\Doctrine\Serializer\Normalizer\CollectionDenormalizer;
 use Symfony\Component\PropertyAccess\PropertyAccessor;
 use Symfony\Component\PropertyAccess\PropertyAccessorInterface;
 use Symfony\Component\Serializer\Exception\MissingConstructorArgumentsException;
@@ -59,6 +60,8 @@
 use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
 use Symfony\Component\Serializer\SerializerInterface;
 use Symfony\Component\TypeInfo\Type;
+use Symfony\Component\TypeInfo\Type\ObjectType;
+use Symfony\Component\TypeInfo\TypeIdentifier;
 
 /**
  * @author Amrouche Hamza <hamza.simperfit@gmail.com>
@@ -1242,6 +1245,68 @@ public function testDenormalizeNullableCollectionOfBackedEnums(): void
         $this->assertInstanceOf(Dummy::class, $actual);
     }
 
+    public function testDenormalizeCollectionWithAClassContainer(): void
+    {
+        $data = ['relatedDummies' => [['name' => 'foo']]];
+
+        $propertyNameCollectionFactory = $this->createStub(PropertyNameCollectionFactoryInterface::class);
+        $propertyNameCollectionFactory->method('create')->willReturn(new PropertyNameCollection(['relatedDummies']));
+
+        // The property declares a Doctrine collection class and a value type that is not an API
+        // resource, so the element type has to travel through the context instead of the type.
+        $propertyMetadataFactory = $this->createStub(PropertyMetadataFactoryInterface::class);
+        $propertyMetadataFactory->method('create')->willReturn(
+            (new ApiProperty())
+                ->withNativeType(Type::collection(Type::object(ArrayCollection::class), Type::object(RelatedDummy::class), Type::int()))
+                ->withWritable(true)
+        );
+
+        $resourceClassResolver = $this->createStub(ResourceClassResolverInterface::class);
+        $resourceClassResolver->method('isResourceClass')->willReturnMap([
+            [Dummy::class, true],
+            [RelatedDummy::class, false],
+            [ArrayCollection::class, false],
+        ]);
+        $resourceClassResolver->method('getResourceClass')->willReturnMap([
+            [null, Dummy::class, Dummy::class],
+        ]);
+
+        $relatedDummy = new RelatedDummy();
+        $collection = new ArrayCollection([$relatedDummy]);
+
+        // Symfony 8.2 and later ship the Doctrine collection denormalizer, so the declared
+        // collection class is handed to the Serializer with the element and key types in the
+        // context. Earlier versions keep the "Foo[]" type and build a plain array.
+        $supportsCollectionClass = class_exists(CollectionDenormalizer::class);
+
+        $propertyAccessor = $this->createMock(PropertyAccessorInterface::class);
+        $propertyAccessor->expects($this->once())
+            ->method('setValue')
+            ->with($this->isInstanceOf(Dummy::class), 'relatedDummies', $supportsCollectionClass ? $collection : [$relatedDummy]);
+
+        $iriConverter = $this->createStub(IriConverterInterface::class);
+
+        $serializerProphecy = $this->prophesize(SerializerInterface::class);
+        $serializerProphecy->willImplement(DenormalizerInterface::class);
+
+        if ($supportsCollectionClass) {
+            $serializerProphecy->denormalize($data['relatedDummies'], ArrayCollection::class, null, Argument::that(static function (array $context): bool {
+                return $context['value_type'] instanceof ObjectType
+                    && RelatedDummy::class === $context['value_type']->getClassName()
+                    && $context['key_type']->isIdentifiedBy(TypeIdentifier::INT);
+            }))->willReturn($collection);
+        } else {
+            $serializerProphecy->denormalize($data['relatedDummies'], RelatedDummy::class.'[]', null, Argument::type('array'))->willReturn([$relatedDummy]);
+        }
+
+        $normalizer = new class($propertyNameCollectionFactory, $propertyMetadataFactory, $iriConverter, $resourceClassResolver, $propertyAccessor, null, null, [], null, null) extends AbstractItemNormalizer {};
+        $normalizer->setSerializer($serializerProphecy->reveal());
+
+        $actual = $normalizer->denormalize($data, Dummy::class);
+
+        $this->assertInstanceOf(Dummy::class, $actual);
+    }
+
     public function testDenormalizeWrongTypedValueForNullableObjectPropertyPreservesNormalizerException(): void
     {
         // What Symfony's DateTimeNormalizer throws for a value it cannot parse.