Symfony version(s) affected

6.2.7

Description

Hey.

I'm using symfony/validator as a standalone package to validate DTOs that come from frontend. To handle optional values (i.e. those that can be missing from the payload), I use a special MissingValue type in a union with the type I want (see reproduction).

I then use a custom ConstraintValidatorFactory to skip validation of MissingValue values. It all plays out very nicely, but there's one place where symfony/validator is not expecting a union: https://github.com/symfony/validator/blob/6.2/Mapping/ClassMetadata.php#L197

Here $property->getType() returns a ReflectionUnionType, while ReflectionNamedType is expected, so it throws an error for a missing ->getName() method.

How to reproduce

enum MissingValue
{
    case INSTANCE;
}

#[Cascade]
class InputDTO {
    #[Length(min: 1, max: 500)]
    public readonly string|null|MissingValue $optionalField = MissingValue::INSTANCE;
}

$validator->validate(new InputDTO());

Possible Solution

I'm aware my use case is not directly supported by symfony/validator, but this could be an easy fix: remove this check altogether, adding a #[Valid] attribute to every field regardless of it's type.

Additional Context

No response