Simplified caching of template context processors.

django/template/context.py

@@ -1,8 +1,9 @@
 from copy import copy
+
+from django.conf import settings
+from django.utils import lru_cache
 from django.utils.module_loading import import_string
 
-# Cache of actual callables.
-_standard_context_processors = None
 # Hard-coded processor for easier use of CSRF protection.
 _builtin_context_processors = ('django.core.context_processors.csrf',)
 
@@ -170,21 +171,11 @@ class RenderContext(BaseContext):
         return self.dicts[-1][key]
 
 
-# This is a function rather than module-level procedural code because we only
-# want it to execute if somebody uses RequestContext.
+@lru_cache.lru_cache()
 def get_standard_processors():
-    from django.conf import settings
-    global _standard_context_processors
-    if _standard_context_processors is None:
-        processors = []
-        collect = []
-        collect.extend(_builtin_context_processors)
-        collect.extend(settings.TEMPLATE_CONTEXT_PROCESSORS)
-        for path in collect:
-            func = import_string(path)
-            processors.append(func)
-        _standard_context_processors = tuple(processors)
-    return _standard_context_processors
+    context_processors = _builtin_context_processors
+    context_processors += tuple(settings.TEMPLATE_CONTEXT_PROCESSORS)
+    return tuple(import_string(path) for path in context_processors)
 
 
 class RequestContext(Context):

django/test/signals.py

@@ -80,8 +80,8 @@ def update_connections_time_zone(**kwargs):
 @receiver(setting_changed)
 def clear_context_processors_cache(**kwargs):
     if kwargs['setting'] == 'TEMPLATE_CONTEXT_PROCESSORS':
-        from django.template import context
-        context._standard_context_processors = None
+        from django.template.context import get_standard_processors
+        get_standard_processors.cache_clear()
 
 
 @receiver(setting_changed)

tests/test_client_regress/context_processors.py

@@ -0,0 +1,2 @@
+def special(request):
+    return {'path': request.special_path}

tests/test_client_regress/tests.py

@@ -9,7 +9,6 @@ import itertools
 
 from django.core.urlresolvers import reverse, NoReverseMatch
 from django.template import TemplateSyntaxError, Context, Template
-import django.template.context
 from django.test import Client, TestCase, override_settings
 from django.test.client import encode_file, RequestFactory
 from django.test.utils import ContextList, str_prefix
@@ -994,12 +993,11 @@ class ContextTests(TestCase):
         # Need to insert a context processor that assumes certain things about
         # the request instance. This triggers a bug caused by some ways of
         # copying RequestContext.
-        try:
-            django.template.context._standard_context_processors = (lambda request: {'path': request.special_path},)
+        with self.settings(TEMPLATE_CONTEXT_PROCESSORS=(
+            'test_client_regress.context_processors.special',
+        )):
             response = self.client.get("/request_context_view/")
             self.assertContains(response, 'Path: /request_context_view/')
-        finally:
-            django.template.context._standard_context_processors = None
 
     def test_nested_requests(self):
         """