"AttributeError: 'property' object has no attribute 'get'" when using Depends in FastAPI

To implement authentication for a FastAPI endpoint, I want to make use of the Depends functionality offered in the latest versions (>=0.95) of FastAPI. I have tried several ways to implement it but I am facing an error "AttributeError: 'property' object has no attribute 'get'". This implies that the starlette Request object is not recognised as such when using Depends.

Endpoint implementation:

@app.get("/")
async def home(user: Annotated[User, Depends(authenticate_request(Request))]):
    """
    status _summary_
    Returns status message if service is running
    """
    if isinstance(user, User):
        return {"Welcome, service is running ok!"}
    raise HTTPException(
        status_code=401,
        detail="User not authorized!",
    )

Function authenticate_request checks validity of cookies based on provided Request:

def authenticate_request(request: Request) -> User:
    cookie1 = request.cookies.get("x")
    cookie2 = request.cookies.get("y")
    if cookie1 is not None and cookie2 is not None:
        tenant = get_tenant(request)
        if user := authenticate_cookies(cookie1, cookie2, tenant):
            if not tenant.startswith(user.tenant):
                print("Unauthorized: Token hostname mismatch")
                raise Exception("Token hostname mismatch")
            return user
    print("Unauthorized: please login")
    raise HTTPException(status_code=401, detail="Unauthorized: please login")

This results in error "AttributeError: 'property' object has no attribute 'get'". This implies that the Request object is not passed correctly or is not recognised as such.

I then tried to solve this without using Depends:

@app.get("/")
async def home(request: Request):
    """
    status _summary_
    Returns status message if service is running
    """
    user = authenticate_request(request=request)
    if isinstance(user, User):
        return {"Welcome, service is running ok!"}
    raise HTTPException(
        status_code=401,
        detail="User not authorized!",
    )

This is working correctly. If no valid cookie is provided a 401 is returned. Based on this I come to the conclusion that my authenticate_request() function is working correctly.

Does anybody know why there is a difference in behaviour between Depends() and the alternative solution?

Help is much appreciated!

Regards,
Laurens

When using Depends(), you just need to pass the name of the dependency function within the brackets. As described in the documentation:

> Let's first focus on the dependency.
>
> It is just a function that can take all the same parameters that a
> path operation function can take.
>
> And it has the same shape and structure that all your path operation
> functions have.
>
> You can think of it as a path operation function without the
> "decorator" (without the @app.get("/some-path")).
>
> And it can return anything you want.

Thus, any other parameters that your dependency function takes, you simply need to declare them in that function and not passing them through Depends(). Same applies to the Request object.

Hence, your path operation function (also known as endpoint) should look like this:

@app.get("/")
async def home(user: Annotated[User, Depends(authenticate_request)]):
    pass

and your authenticate_request dependency function should be as follows:

def authenticate_request(request: Request) -> User:
    pass