How to pass MetadataFactory::create() into SerializationVisitorInterface::startVisitingObject()?

[simPod]

I'm creating metadata for class through $classMetadata = $context->getMetadataFactory()->getMetadataForClass(My::class);

interface MetadataFactoryInterface
{
    /**
     * @return ClassHierarchyMetadata|MergeableClassMetadata|null
     */
    public function getMetadataForClass(string $className);

So the return type is ClassHierarchyMetadata|MergeableClassMetadata|null

Though SerializationVisitorInterface::startVisitingObject() expects ClassMetadata which is not contravariant to what MetadataFactoryInterface::getMetadataForClass() returns.

interface SerializationVisitorInterface extends VisitorInterface
{
    public function startVisitingObject(ClassMetadata $metadata, object $data, array $type): void;

How to properly create those metadata and pass them then?

[goetas]

hmmm... did not get it. :-(

can you explain your goal rather than the technical consequence of it?

[simPod]

I'm trying to create class metadata so I can pass them to the visitor.

For that I'm using metadata factory. But it does not return compatible type to be passed into SerializationVisitorInterface:: startVisitingObject() (even though it technically works, the typing is not correct).

I need to pass JMS\Serializer\Metadata\ClassMetadata there but from factory I'm getting ClassHierarchyMetadata|MergeableClassMetadata

Currently what I'm doing is that I have to assert the type to be safe, because I'm not guaranteed by the MetadataFactory I'll receive JMS\Serializer\Metadata\ClassMetadata instance

$classMetadata = $context->getMetadataFactory()->getMetadataForClass(My::class);
Assert::isInstanceOf($classMetadata, \JMS\Serializer\Metadata\ClassMetadata::class);

$visitor->startVisitingObject($classMetadata, $entity, ['name' => get_class($entity)], $context);

So I'm looking for a proper way to get something like

interface MetadataFactoryInterface
{
    public function getMetadataForClass(string $className) : ?\JMS\Serializer\Metadata\ClassMetadata;

That said to receive ClassMetadata instance that I can safely pass into a visitor. Passing ClassHierarchyMetadata|MergeableClassMetadata does not seem to be type safe.

[goetas]

$classMetadata = $context->getMetadataFactory()->getMetadataForClass(My::class); should "almost always" return some metadata (despite its signature), so if you get NULL, something is wrong with your configs...
did you disable the annotation metadata reader?

[simPod]

The null is not issue. The issue is that it returns ClassHierarchyMetadata|MergeableClassMetadata metadata types while visitor requires \JMS\Serializer\Metadata\ClassMetadata which is not contra variant.

[goetas]

did you customize MetadataFactory ? by providing your own implementation? (that class should choose the right metadata...)

[simPod]

Yes, it gives correct type actually. When executed, it returns \JMS\Serializer\Metadata\ClassMetadata. There's no issue with running the code. This is about API.

I'd like to rely on the interfaces and these two are incompatible:

MetadataFactoryInterface::getMetadataForClass(...) : ClassHierarchyMetadata|MergeableClassMetadata|null;
SerializationVisitorInterface:: startVisitingObject(\JMS\Serializer\Metadata\ClassMetadata, ...);

so it works but it's not correct in terms of interface type compatibility. I cannot pass return type ClassHierarchyMetadata|MergeableClassMetadata where \JMS\Serializer\Metadata\ClassMetadata is expected. It's not covariant.

[goetas]

well, I'm aware that this library is not fully type safe. Adding phpstan/psalm is a lot of work (and making it type-safe would require BC breaks for sure).

Is one day someone will be interested to work on adding static analysis, that would be nice!

[simPod]

Ah ok, I was wondering whether I'm doing something wrong or not. Thanks!