[QUESTION] dependencies inherited from typing.Generic

How can I avoid ‘args’ and ‘kwargs’ as a required query parameters if I use typing.Generic?

I have got next generic base class

from typing import Generic, Type, TypeVar

ModelType = TypeVar("ModelType", bound=BaseModel)
CreateSchemaType = TypeVar("CreateSchemaType", bound=BaseModel)
UpdateSchemaType = TypeVar("UpdateSchemaType", bound=BaseModel)

class CRUDBase(Generic[ModelType, CreateSchemaType, UpdateSchemaType]):

    def __init__(self, db: Database, table: Table, model: Type[ModelType]):
        self.db = db
        self.model = model
        self.table = table

And successor class which used as a dependency

class UserService(CRUDBase[User, UserCreate, UserUpdate]):
    def __init__(self, db: Database = Depends(get_db)):
        super().__init__(db, UserTable, User)

Since typing.Generic has overwritten __new__ method, so FastAPI makes args and kwargs as a required query attributes.

I have only one solution with a factory function, have you another solution?

[dardosordi]

Got it working somehow with this decorator.

def restore_signature(cls):
    @functools.wraps(cls)
    def wrap(*args, **kwargs):
        return cls(*args, **kwargs)

    sig = inspect.signature(cls.__init__)
    parameters = list(sig.parameters.values())[1:]

    wrap.__signature__ = sig.replace(parameters=parameters)
    return wrap

[dardosordi]

@dardosordi Could you please share detail how you get it working?

class BaseService(Generic[ModelType, CreateSchemaType, UpdateSchemaType]):
    def __init__(self, model: Type[ModelType], db: Session):
      """Base class for generic service"""

@generic_dependency
class UserService(BaseService[User, UserCreate, UserUpdate]):
    def __init__(self, db: Session = Depends(get_db)):
        super().__init__(User, db)

@router.post("/signup")
def signup(user_service: UserService = Depends()):