How to add a custom decorator to a FastAPI route?

I want to add an auth_required decorator to my endpoints. (Please consider that this question is about decorators, not middleware)

So a simple decorator looks like this:

def auth_required(func):
    def wrapper(*args, **kwargs):
        if user_ctx.get() is None:
            raise HTTPException(...)
        return func(*args, **kwargs)
    return wrapper

So there are 2 usages:

@auth_required
@router.post(...)

or

@router.post(...)
@auth_required

The first way doesn't work because router.post creates a router that saved into self.routes of APIRouter object. The second way doesn't work because it fails to verify pydantic object. For any request model, it says missing args, missing kwargs.

So my question is - how can I add any decorators to FastAPI endpoints? Should I get into router.routes and modify the existing endpoint? Or use some functools.wraps like functions?

from How to add a custom decorator to a FastAPI route?