[1.2.X] Fixed #13283 -- Corrected CACHE_MIDDLEWARE_ANONYMOUS_ONLY's bad habit of setting Vary: Cookie on all responses and destroying cache efficiency. Thanks to natrius for the fix.

Backport of r15381 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15382 bcc190cf-cafb-0310-a4f2-bffc1f526a37

5 files changed, 57 insertions, 11 deletions

diff --git a/django/middleware/cache.py b/django/middleware/cache.py
index 3f602fe652..32d15b4095 100644
--- a/django/middleware/cache.py
+++ b/django/middleware/cache.py
@@ -50,7 +50,8 @@ More details about how the caching works:
 
 from django.conf import settings
 from django.core.cache import cache
-from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers, get_max_age
+from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers, get_max_age, has_vary_header
+
 
 class UpdateCacheMiddleware(object):
     """
@@ -66,9 +67,19 @@ class UpdateCacheMiddleware(object):
         self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
         self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False)
 
+    def _should_update_cache(self, request, response):
+        if not hasattr(request, '_cache_update_cache') or not request._cache_update_cache:
+            return False
+        if self.cache_anonymous_only and has_vary_header(response, 'Cookie'):
+            assert hasattr(request, 'user'), "The Django cache middleware with CACHE_MIDDLEWARE_ANONYMOUS_ONLY=True requires authentication middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.auth.middleware.AuthenticationMiddleware' before the CacheMiddleware."
+            if request.user.is_authenticated():
+                # Don't cache user-variable requests from authenticated users.
+                return False
+        return True
+
     def process_response(self, request, response):
         """Sets the cache, if needed."""
-        if not hasattr(request, '_cache_update_cache') or not request._cache_update_cache:
+        if not self._should_update_cache(request, response):
             # We don't need to update the cache, just return.
             return response
         if request.method != 'GET':
@@ -112,17 +123,10 @@ class FetchFromCacheMiddleware(object):
         Checks whether the page is already cached and returns the cached
         version if available.
         """
-        if self.cache_anonymous_only:
-            assert hasattr(request, 'user'), "The Django cache middleware with CACHE_MIDDLEWARE_ANONYMOUS_ONLY=True requires authentication middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.auth.middleware.AuthenticationMiddleware' before the CacheMiddleware."
-
         if not request.method in ('GET', 'HEAD') or request.GET:
             request._cache_update_cache = False
             return None # Don't bother checking the cache.
 
-        if self.cache_anonymous_only and request.user.is_authenticated():
-            request._cache_update_cache = False
-            return None # Don't cache requests from authenticated users.
-
         cache_key = get_cache_key(request, self.key_prefix)
         if cache_key is None:
             request._cache_update_cache = True
diff --git a/django/utils/cache.py b/django/utils/cache.py
index 6cfd893668..58d087b079 100644
--- a/django/utils/cache.py
+++ b/django/utils/cache.py
@@ -134,6 +134,16 @@ def patch_vary_headers(response, newheaders):
                           if newheader.lower() not in existing_headers]
     response['Vary'] = ', '.join(vary_headers + additional_headers)
 
+def has_vary_header(response, header_query):
+    """
+    Checks to see if the response has a given header name in its Vary header.
+    """
+    if not response.has_header('Vary'):
+        return False
+    vary_headers = cc_delim_re.split(response['Vary'])
+    existing_headers = set([header.lower() for header in vary_headers])
+    return header_query.lower() in existing_headers
+
 def _i18n_cache_key_suffix(request, cache_key):
     """If enabled, returns the cache key ending with a locale."""
     if settings.USE_I18N:
diff --git a/tests/regressiontests/cache/tests.py b/tests/regressiontests/cache/tests.py
index 7167e2fbf8..e53194d82c 100644
--- a/tests/regressiontests/cache/tests.py
+++ b/tests/regressiontests/cache/tests.py
@@ -4,7 +4,6 @@
 # Uses whatever cache backend is set in the test settings file.
 
 import os
-import shutil
 import tempfile
 import time
 import unittest
@@ -13,9 +12,10 @@ import warnings
 from django.conf import settings
 from django.core import management
 from django.core.cache import get_cache
-from django.core.cache.backends.base import InvalidCacheBackendError, CacheKeyWarning
+from django.core.cache.backends.base import CacheKeyWarning
 from django.http import HttpResponse, HttpRequest
 from django.middleware.cache import FetchFromCacheMiddleware, UpdateCacheMiddleware
+from django.test import TestCase
 from django.test.utils import get_warnings_state, restore_warnings_state
 from django.utils import translation
 from django.utils.cache import patch_vary_headers, get_cache_key, learn_cache_key
@@ -648,5 +648,28 @@ class CacheI18nTest(unittest.TestCase):
         get_cache_data = FetchFromCacheMiddleware().process_request(request)
         self.assertEqual(get_cache_data.content, es_message)
 
+
+class CacheMiddlewareAnonymousOnlyTests(TestCase):
+    urls = 'regressiontests.cache.urls'
+
+    def setUp(self):
+        self._orig_cache_middleware_anonymous_only = \
+            getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False)
+        self._orig_middleware_classes = settings.MIDDLEWARE_CLASSES
+
+        settings.MIDDLEWARE_CLASSES = list(settings.MIDDLEWARE_CLASSES)
+        settings.MIDDLEWARE_CLASSES.insert(0, 'django.middleware.cache.UpdateCacheMiddleware')
+        settings.MIDDLEWARE_CLASSES += ['django.middleware.cache.FetchFromCacheMiddleware']
+
+    def tearDown(self):
+        settings.CACHE_MIDDLEWARE_ANONYMOUS_ONLY = self._orig_cache_middleware_anonymous_only
+        settings.MIDDLEWARE_CLASSES = self._orig_middleware_classes
+
+    def test_cache_middleware_anonymous_only_does_not_cause_vary_cookie(self):
+        settings.CACHE_MIDDLEWARE_ANONYMOUS_ONLY = True
+        response = self.client.get('/')
+        self.failIf('Cookie' in response.get('Vary', ''))
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/regressiontests/cache/urls.py b/tests/regressiontests/cache/urls.py
new file mode 100644
index 0000000000..b98447bfa3
--- /dev/null
+++ b/tests/regressiontests/cache/urls.py
@@ -0,0 +1,5 @@
+from django.conf.urls.defaults import patterns
+
+urlpatterns = patterns('regressiontests.cache.views',
+    (r'^$', 'home'),
+)
diff --git a/tests/regressiontests/cache/views.py b/tests/regressiontests/cache/views.py
new file mode 100644
index 0000000000..9b72f03f56
--- /dev/null
+++ b/tests/regressiontests/cache/views.py
@@ -0,0 +1,4 @@
+from django.http import HttpResponse
+
+def home(request):
+    return HttpResponse('Hello World!')