Fixed #6552, #12031 - Make django.core.context_processors.auth lazy to avoid "Vary: Cookie"

Thanks to olau@iola.dk, Suor for the report



git-svn-id: http://code.djangoproject.com/svn/django/trunk@11623 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/auth/tests/remote_user.py

@@ -2,7 +2,7 @@ from datetime import datetime
 
 from django.conf import settings
 from django.contrib.auth.backends import RemoteUserBackend
-from django.contrib.auth.models import AnonymousUser, User
+from django.contrib.auth.models import User
 from django.test import TestCase
 
 
@@ -30,15 +30,15 @@ class RemoteUserTest(TestCase):
         num_users = User.objects.count()
 
         response = self.client.get('/remote_user/')
-        self.assert_(isinstance(response.context['user'], AnonymousUser))
+        self.assert_(response.context['user'].is_anonymous())
         self.assertEqual(User.objects.count(), num_users)
 
         response = self.client.get('/remote_user/', REMOTE_USER=None)
-        self.assert_(isinstance(response.context['user'], AnonymousUser))
+        self.assert_(response.context['user'].is_anonymous())
         self.assertEqual(User.objects.count(), num_users)
 
         response = self.client.get('/remote_user/', REMOTE_USER='')
-        self.assert_(isinstance(response.context['user'], AnonymousUser))
+        self.assert_(response.context['user'].is_anonymous())
         self.assertEqual(User.objects.count(), num_users)
 
     def test_unknown_user(self):
@@ -115,7 +115,7 @@ class RemoteUserNoCreateTest(RemoteUserTest):
     def test_unknown_user(self):
         num_users = User.objects.count()
         response = self.client.get('/remote_user/', REMOTE_USER='newuser')
-        self.assert_(isinstance(response.context['user'], AnonymousUser))
+        self.assert_(response.context['user'].is_anonymous())
         self.assertEqual(User.objects.count(), num_users)
 
 

django/core/context_processors.py

@@ -8,6 +8,27 @@ RequestContext.
 """
 
 from django.conf import settings
+from django.utils.functional import lazy, memoize, LazyObject
+
+class ContextLazyObject(LazyObject):
+    """
+    A lazy object initialised from any function, useful for lazily
+    adding things to the Context.
+
+    Designed for compound objects of unknown type. For simple objects of known
+    type, use django.utils.functional.lazy.
+    """
+    def __init__(self, func):
+        """
+        Pass in a callable that returns the actual value to be used
+        """
+        self.__dict__['_setupfunc'] = func
+        # For some reason, we have to inline LazyObject.__init__ here to avoid
+        # recursion
+        self._wrapped = None
+
+    def _setup(self):
+        self._wrapped = self._setupfunc()
 
 def auth(request):
     """
@@ -17,15 +38,26 @@ def auth(request):
     If there is no 'user' attribute in the request, uses AnonymousUser (from
     django.contrib.auth).
     """
-    if hasattr(request, 'user'):
-        user = request.user
-    else:
-        from django.contrib.auth.models import AnonymousUser
-        user = AnonymousUser()
+    # 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': user,
-        'messages': user.get_and_delete_messages(),
-        'perms': PermWrapper(user),
+        'user': ContextLazyObject(get_user),
+        'messages': lazy(memoize(lambda: get_user().get_and_delete_messages(), {}, 0), list)(),
+        'perms':  lazy(lambda: PermWrapper(get_user()), PermWrapper)(),
     }
 
 def debug(request):
@@ -79,7 +111,7 @@ class PermWrapper(object):
 
     def __getitem__(self, module_name):
         return PermLookupDict(self.user, module_name)
-        
+
     def __iter__(self):
         # I am large, I contain multitudes.
         raise TypeError("PermWrapper is not iterable.")

tests/regressiontests/context_processors/fixtures/context-processors-users.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<django-objects version="1.0">
+    <object pk="100" model="auth.user">
+        <field type="CharField" name="username">super</field>
+        <field type="CharField" name="first_name">Super</field>
+        <field type="CharField" name="last_name">User</field>
+        <field type="CharField" name="email">super@example.com</field>
+        <field type="CharField" name="password">sha1$995a3$6011485ea3834267d719b4c801409b8b1ddd0158</field>
+        <field type="BooleanField" name="is_staff">True</field>
+        <field type="BooleanField" name="is_active">True</field>
+        <field type="BooleanField" name="is_superuser">True</field>
+        <field type="DateTimeField" name="last_login">2007-05-30 13:20:10</field>
+        <field type="DateTimeField" name="date_joined">2007-05-30 13:20:10</field>
+        <field to="auth.group" name="groups" rel="ManyToManyRel"></field>
+        <field to="auth.permission" name="user_permissions" rel="ManyToManyRel"></field>
+    </object>
+</django-objects>

tests/regressiontests/context_processors/templates/context_processors/auth_attrs_access.html

@@ -0,0 +1 @@
+{{ user }}

tests/regressiontests/context_processors/templates/context_processors/auth_attrs_messages.html

@@ -0,0 +1 @@
+{% for m in messages %}{{ m }}{% endfor %}

tests/regressiontests/context_processors/templates/context_processors/auth_attrs_no_access.html

@@ -0,0 +1 @@
+ 

tests/regressiontests/context_processors/templates/context_processors/auth_attrs_perms.html

@@ -0,0 +1 @@
+{% if perms.auth %}Has auth permissions{% endif %}

tests/regressiontests/context_processors/templates/context_processors/auth_attrs_test_access.html

@@ -0,0 +1 @@
+{% if session_accessed %}Session accessed{% else %}Session not accessed{% endif %}

tests/regressiontests/context_processors/templates/context_processors/auth_attrs_user.html

@@ -0,0 +1,3 @@
+unicode: {{ user }}
+id: {{ user.id }}
+username: {{ user.username }}

tests/regressiontests/context_processors/tests.py

@@ -36,3 +36,46 @@ class RequestContextProcessorTests(TestCase):
         self.assertContains(response, url)
         response = self.client.post(url, {'path': '/blah/'})
         self.assertContains(response, url)
+
+class AuthContextProcessorTests(TestCase):
+    """
+    Tests for the ``django.core.context_processors.auth`` processor
+    """
+    urls = 'regressiontests.context_processors.urls'
+    fixtures = ['context-processors-users.xml']
+
+    def test_session_not_accessed(self):
+        """
+        Tests that the session is not accessed simply by including
+        the auth context processor
+        """
+        response = self.client.get('/auth_processor_no_attr_access/')
+        self.assertContains(response, "Session not accessed")
+
+    def test_session_is_accessed(self):
+        """
+        Tests that the session is accessed if the auth context processor
+        is used and relevant attributes accessed.
+        """
+        response = self.client.get('/auth_processor_attr_access/')
+        self.assertContains(response, "Session accessed")
+
+    def test_perms_attrs(self):
+        self.client.login(username='super', password='secret')
+        response = self.client.get('/auth_processor_perms/')
+        self.assertContains(response, "Has auth permissions")
+
+    def test_message_attrs(self):
+        self.client.login(username='super', password='secret')
+        response = self.client.get('/auth_processor_messages/')
+        self.assertContains(response, "Message 1")
+
+    def test_user_attrs(self):
+        """
+        Test that ContextLazyObject wraps objects properly
+        """
+        self.client.login(username='super', password='secret')
+        response = self.client.get('/auth_processor_user/')
+        self.assertContains(response, "unicode: super")
+        self.assertContains(response, "id: 100")
+        self.assertContains(response, "username: super")

tests/regressiontests/context_processors/urls.py

@@ -5,4 +5,9 @@ import views
 
 urlpatterns = patterns('',
     (r'^request_attrs/$', views.request_processor),
+    (r'^auth_processor_no_attr_access/$', views.auth_processor_no_attr_access),
+    (r'^auth_processor_attr_access/$', views.auth_processor_attr_access),
+    (r'^auth_processor_user/$', views.auth_processor_user),
+    (r'^auth_processor_perms/$', views.auth_processor_perms),
+    (r'^auth_processor_messages/$', views.auth_processor_messages),
 )

tests/regressiontests/context_processors/views.py

@@ -6,3 +6,29 @@ from django.template.context import RequestContext
 def request_processor(request):
     return render_to_response('context_processors/request_attrs.html',
         RequestContext(request, {}, processors=[context_processors.request]))
+
+def auth_processor_no_attr_access(request):
+    r1 = render_to_response('context_processors/auth_attrs_no_access.html',
+        RequestContext(request, {}, processors=[context_processors.auth]))
+    # *After* rendering, we check whether the session was accessed
+    return render_to_response('context_processors/auth_attrs_test_access.html',
+        {'session_accessed':request.session.accessed})
+
+def auth_processor_attr_access(request):
+    r1 = render_to_response('context_processors/auth_attrs_access.html',
+        RequestContext(request, {}, processors=[context_processors.auth]))
+    return render_to_response('context_processors/auth_attrs_test_access.html',
+        {'session_accessed':request.session.accessed})
+
+def auth_processor_user(request):
+    return render_to_response('context_processors/auth_attrs_user.html',
+        RequestContext(request, {}, processors=[context_processors.auth]))
+
+def auth_processor_perms(request):
+    return render_to_response('context_processors/auth_attrs_perms.html',
+        RequestContext(request, {}, processors=[context_processors.auth]))
+
+def auth_processor_messages(request):
+    request.user.message_set.create(message="Message 1")
+    return render_to_response('context_processors/auth_attrs_messages.html',
+         RequestContext(request, {}, processors=[context_processors.auth]))