🚀 New issue to wemake-services/django-modern-rest by @LesPrimus
📝 UnsolvableAnnotationsError when subclassing a concrete Controller subclass` (#873)


What's wrong?

Bug: UnsolvableAnnotationsError when subclassing a concrete Controller subclass

Description

When creating an intermediate concrete controller class and then subclassing it,
__init_subclass__ raises UnsolvableAnnotationsError even though the serializer
is already resolved on the parent.

Reproduction

from dmr import Controller
from dmr.plugins.pydantic import PydanticSerializer
from dmr.serializer import BaseSerializer
                                                                                                                                                                            
 
class BaseController[T: BaseSerializer](Controller[T]):                                                                                                                     
    pass        


class PydanticController(BaseController[PydanticSerializer]):
    pass


# This raises UnsolvableAnnotationsError
class UserController(PydanticController):
    def get(self) -> ...:
        ...                                                                                                                                                                 
 
Error                                                                                                                                                                       
                
dmr.exceptions.UnsolvableAnnotationsError: Type args () are not correct for <class 'UserController'>,
at least 1 type arg must be provided

Expected behavior

UserController should inherit the serializer from its concrete parent PydanticController,                                                                                   
which already has serializer = PydanticSerializer set.


--

Thanks for the awesome library, I just started exploring it and I'm really enjoying it so far!

--

### How it should be?

Subclassing a concrete `Controller` subclass (one that already has a resolved serializer)                                                                                   
should work without requiring the type argument to be re-specified.                                                                                                         
                                                                                                                                                                            
`UserController(PydanticController)` should behave the same as `UserController(BaseController[PydanticSerializer])`.

### Used versions

- `django-modern-rest==0.5.0`                                                                                                                                               
-  `Python 3.14.0` 

### OS information

- `Linux tuxedo-stellaris 6.17.0-111019-tuxedo x86_64 (Ubuntu 24.04)`

#bug #good_first_issue #help_wanted #django_modern_rest
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