Path Parameters in Advanced Dependency

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Example Code

@router.get("/{project_id}/team}", response_model=List[schemas.team])
def get_team(
    project_id: UUID,
    is_authorized: bool = Depends(deps.AuthorizationCheck(project_id=project_id))
) -> Any:
# Get the Team through crud operations
 pass

class AuthorizationCheck:
    def __init__(self, project_id) -> None:
        self.project_id = project_id

    def __call__(self, air_data_session: Session = Depends(session),
    auth_id: str = Depends(get_firebase_auth_id)) -> bool:
        if not crud.user.is_user_part_of_module_and_project(
        session,
        project_id=str(self.project_id),
        firebase_auth_id=auth_id,
        ):
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="User not part of project",
            )
        return True

Description

I’m implementing a dependency that checks if the user is allowed to access a certain project or not. If they are not allowed, the dependency will raise a 401 exception otherwise, it will return true.

The project_id is provided through the path parameter and several APIs will be using this dependency. Here’s an example of one of the API that is supposed to fetch the team working on a specific project api/v2/{project_id}/team

As an attempt, I created a dependency class called AuthorizationCheck that takes as input project_id. However, project_id is not being recognized from the path parameter.

I’ve read the Advanced Dependency tutorial provided in the documentation but it doesn’t mention a way to use the path parameters in it. Is this doable?

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.54.2

Python Version

3.9.6

Additional Context

No response

[gitnarqt]

@frankie567 Merci beaucoup!! It’s exactly what I wanted 🎉

[frankie567]

The problem here is that you are using a value that will be available at runtime, project_id, at “compile time”:

Actually, all you have to do is to change your __call__ method so that it injects project_id. That’s the beauty of FastAPI: dependencies are 100% recursive:

@router.get("/{project_id}/team}", response_model=List[schemas.team])
def get_team(
    project_id: UUID,
    is_authorized: bool = Depends(deps.AuthorizationCheck())
) -> Any:
# Get the Team through crud operations
 pass


class AuthorizationCheck:
    def __call__(self, project_id: UUID, air_data_session: Session = Depends(session), auth_id: str = Depends(get_firebase_auth_id)) -> bool:
        if not crud.user.is_user_part_of_module_and_project(
            session,
            project_id=str(project_id),
            firebase_auth_id=auth_id,
        ):
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="User not part of project",
            )
        return True

If you don’t need to manage other parameters, a class may be unnecessary, you can do it with a simple function:

@router.get("/{project_id}/team}", response_model=List[schemas.team])
def get_team(
    project_id: UUID,
    is_authorized: bool = Depends(deps.is_authorized)
) -> Any:
# Get the Team through crud operations
 pass


def is_authorized(self, project_id: UUID, air_data_session: Session = Depends(session), auth_id: str = Depends(get_firebase_auth_id)) -> bool:
    if not crud.user.is_user_part_of_module_and_project(
        session,
        project_id=str(project_id),
        firebase_auth_id=auth_id,
    ):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not part of project",
        )
    return True

Even better, if you don’t need the return value, you can just inject this dependency in the route decorator:

@router.get(
    "/{project_id}/team}",
    response_model=List[schemas.team],
    dependencies=[Depends(deps.is_authorized)],
)
def get_team(project_id: UUID) -> Any:
# Get the Team through crud operations
    pass

You can reuse this dependency at will. The only thing you have to take care of is to put the project_id parameter in your path pattern. Otherwise, FastAPI will automatically look for it in query parameters.