Add role specific `get_context_data` methods

Recently I have found myself working on a CRUDView for a complex model with relationships to a bunch of ancillary models. The get_context_data method has started to become a bit overstuffed with variables I only ever need for one role or another.

It would be nice if the view offered something for role specific contexts, similar to get_FOO_display for model choices.

After playing around a bit, I quite like where I landed in my CRUDView subclass:

def get_context_data(self, **kwargs: object) -> dict[str, object]:
    context = super().get_context_data(**kwargs)
    role_context = self.get_role_context_data(context, **kwargs)
    if role_context is not None:
        context.update(role_context)
    return context

def get_role_context_data(
    self, context: dict[str, object], **kwargs: object
  ) -> dict[str, object] | None:
    if not hasattr(self, "role"):
        return None

    func_name = f"get_{self.role.value}_context_data"
    func = getattr(self, func_name, None)

    if func is None or not callable(func):
        return None

    role_context = func(context=context, **kwargs)

    if not isinstance(role_context, dict):
        msg = f"`{func_name}` must return a dictionary"
        raise ValueError(msg)

    return role_context

This allows for defining role specific context data functions, e.g. get_create_context_data - key line being role_context = func(context=context, **kwargs). They need to be defined with **kwargs and return a dict as I have it now, but you could probably even do away with the kwargs requirement somehow if desired.

carltongibson / neapolitan

Add role specific `get_context_data` methods #57