from django.core.context_processors import PermWrapper
from django.utils.functional import lazy,memoize,SimpleLazyObject
from django.contrib import messages
def auth(request):
"""
Returns context variables required by apps that use Django's authentication
system.
If there is no 'user' attribute in the request, uses AnonymousUser (from
django.contrib.auth).
"""
# If we access request.user, request.session is accessed, which results in
# 'Vary: Cookie' being sent in every request that uses this context
# processor, which can easily be every request on a site if
# TEMPLATE_CONTEXT_PROCESSORS has this context processor added. This kills
# the ability to cache. So, we carefully ensure these attributes are lazy.
# We don't use django.utils.functional.lazy() for User, because that
# requires knowing the class of the object we want to proxy, which could
# break with custom auth backends. LazyObject is a less complete but more
# flexible solution that is a good enough wrapper for 'User'.
def get_user():
if hasattr(request, 'user'):
return request.user
else:
from django.contrib.auth.models import AnonymousUser
return AnonymousUser()
return {
'user': SimpleLazyObject(get_user),
'messages': messages.get_messages(request),
'perms': lazy(lambda: PermWrapper(get_user()), PermWrapper)(),
}
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