'Role' object has no attribute '__name__'

Question

I am trying to implement role based permission into my application. I have a decorator role_required into which I can pass a set of user roles and only those user with that role can access that view. I have properly assigned roles to the user but, now I am getting AttributeError stating that 'Role' object has no attribute '__name__'

views.py file:

m_role_required = method_decorator(role_required)
class AddProposal(FormView):

    @m_role_required(roles.space_admin)
    def dispatch(self, *args, **kwargs):
        return super(AddProposal, self).dispatch(*args, **kwargs)

The decorator role_required:

from django.contrib.auth.decorators import user_passes_test
def role_required(*roles):

    def check_role(user):
        return getattr(user, 'role', None) in roles
    return user_passes_test(check_role)

The Role class:

class Roles(object):
    _roles_dict = None

    @property
    def roles_dict(self):

        if self._roles_dict is None:
            self._roles_dict = {}
            for item in self._config:
                if isinstance(item, basestring):
                    # An item like 'manager'
                    self._roles_dict[item] = None
                else:
                    # Anything else
                    raise ImproperlyConfigured(_INCORRECT_ARGS)
        return self._roles_dict

    @property
    def choices(self):

        return [(role, role) for role in self.roles_dict.keys()]

    def __init__(self, config=None):

        self._config = config or getattr(settings, 'USER_ROLES', ())

    def __getattr__(self, name):

        if name in self.roles_dict.keys():
            return Role(name=name)
        else:
            raise AttributeError("No such role exists '%s'" % name)

roles = Roles()

I am not able to find out why this error is being raised. Can anyone help. Let me add the traceback with this,

Environment:

Request Method: GET
Request URL: http://127.0.0.1:8000/en-gb/spaces/bithin/proposal/add/


Traceback:

  48. class AddProposal(FormView):
File "/home/bithin/gsoc/week3/e-cidadania/src/apps/ecidadania/proposals/views.py" in AddProposal
  78.     @m_role_required(roles.space_admin)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _dec
  34.         update_wrapper(_wrapper, func)
File "/usr/lib/python2.7/functools.py" in update_wrapper
  33.         setattr(wrapper, attr, getattr(wrapped, attr))

Exception Type: AttributeError at /en-gb/spaces/bithin/proposal/add/
Exception Value: 'Role' object has no attribute '__name__'

Answer 1

Have a look at the code for django.utils.decorators.method_decorator. The method decorator it returns cannot accept further parameters save for the actual function to decorate. Properties of this function, including its __name__, are copied over via functools.update_wrapper, in the usual Python fashion. You get this error because you pass a Role object instead of a function.

In other words, you need to rewrite your view like this:

space_admin_required = method_decorator(role_required(roles.space_admin))
class AddProposal(FormView):

    @space_admin_required
    def dispatch(self, *args, **kwargs):
        return super(AddProposal, self).dispatch(*args, **kwargs)

Answer 2

This is a potential duplicate of Why do python instances have no __name__ attribute?

Short answer: the name of a class is stored in the class and is not directly available to the instance. You can access the class name of an instance via myinstance.__class__.__name__.