from django.conf import settings from django.contrib.messages.storage import default_storage class MessageMiddleware(object): """ Middleware that handles temporary messages. """ def process_request(self, request): request._messages = default_storage(request) def process_response(self, request, response): """ Updates the storage backend (i.e., saves the messages). If not all messages could not be stored and ``DEBUG`` is ``True``, a ``ValueError`` is raised. """ # A higher middleware layer may return a request which does not contain # messages storage, so make no assumption that it will be there. if hasattr(request, '_messages'): unstored_messages = request._messages.update(response) if unstored_messages and settings.DEBUG: raise ValueError('Not all temporary messages could be stored.') return response