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