Fixed #21351 -- Replaced memoize with Python's lru_cache.

Replaced the custom, untested memoize with a similar decorator from Python's
3.2 stdlib. Although some minor performance degradation (see ticket), it is
expected that in the long run lru_cache will outperform memoize once it is
implemented in C.

Thanks to EvilDMP for the report and Baptiste Mispelon for the idea of
replacing memoize with lru_cache.

4 files changed, 45 insertions, 7 deletions

diff --git a/tests/decorators/tests.py b/tests/decorators/tests.py
index db00f36051..9c654e500a 100644
--- a/tests/decorators/tests.py
+++ b/tests/decorators/tests.py
@@ -1,5 +1,6 @@
 from functools import wraps
 from unittest import TestCase
+import warnings
 
 from django.contrib.admin.views.decorators import staff_member_required
 from django.contrib.auth.decorators import login_required, permission_required, user_passes_test
@@ -58,11 +59,14 @@ full_decorator = compose(
     staff_member_required,
 
     # django.utils.functional
-    lambda f: memoize(f, {}, 1),
     allow_lazy,
     lazy,
 )
 
+# suppress the deprecation warning of memoize
+with warnings.catch_warnings(record=True):
+    fully_decorated = memoize(fully_decorated, {}, 1)
+
 fully_decorated = full_decorator(fully_decorated)
 
 
diff --git a/tests/deprecation/tests.py b/tests/deprecation/tests.py
index 7d9ed16636..2a0922a0a8 100644
--- a/tests/deprecation/tests.py
+++ b/tests/deprecation/tests.py
@@ -4,6 +4,7 @@ import warnings
 from django.test import SimpleTestCase, RequestFactory, override_settings
 from django.utils import six, translation
 from django.utils.deprecation import RenameMethodsBase
+from django.utils.functional import memoize
 
 
 class RenameManagerMethods(RenameMethodsBase):
@@ -205,3 +206,18 @@ class DeprecatedChineseLanguageCodes(SimpleTestCase):
                 "The use of the language code 'zh-tw' is deprecated. "
                 "Please use the 'zh-hant' translation instead.",
             ])
+
+
+class DeprecatingMemoizeTest(SimpleTestCase):
+    def test_deprecated_memoize(self):
+        """
+        Ensure the correct warning is raised when memoize is used.
+        """
+        warnings.simplefilter('always')
+
+        with warnings.catch_warnings(record=True) as recorded:
+            memoize(lambda x: x, {}, 1)
+            msg = str(recorded.pop().message)
+            self.assertEqual(msg,
+                'memoize wrapper is deprecated and will be removed in Django '
+                '1.9. Use django.utils.lru_cache instead.')
diff --git a/tests/staticfiles_tests/tests.py b/tests/staticfiles_tests/tests.py
index 463ab47030..39ce49817c 100644
--- a/tests/staticfiles_tests/tests.py
+++ b/tests/staticfiles_tests/tests.py
@@ -55,7 +55,7 @@ class BaseStaticFilesTestCase(object):
         storage.staticfiles_storage._wrapped = empty
         # Clear the cached staticfile finders, so they are reinitialized every
         # run and pick up changes in settings.STATICFILES_DIRS.
-        finders._finders.clear()
+        finders.get_finder.cache_clear()
 
         testfiles_path = os.path.join(TEST_ROOT, 'apps', 'test', 'static', 'test')
         # To make sure SVN doesn't hangs itself with the non-ASCII characters
@@ -561,7 +561,7 @@ class TestCollectionCachedStorage(BaseCollectionTestCase,
         Test that post_processing indicates the origin of the error when it
         fails. Regression test for #18986.
         """
-        finders._finders.clear()
+        finders.get_finder.cache_clear()
         err = six.StringIO()
         with self.assertRaises(Exception):
             call_command('collectstatic', interactive=False, verbosity=0, stderr=err)
@@ -756,6 +756,15 @@ class TestMiscFinder(TestCase):
         self.assertRaises(ImproperlyConfigured,
             finders.get_finder, 'foo.bar.FooBarFinder')
 
+    def test_cache(self):
+        finders.get_finder.cache_clear()
+        for n in range(10):
+            finders.get_finder(
+                'django.contrib.staticfiles.finders.FileSystemFinder')
+        cache_info = finders.get_finder.cache_info()
+        self.assertEqual(cache_info.hits, 9)
+        self.assertEqual(cache_info.currsize, 1)
+
     @override_settings(STATICFILES_DIRS='a string')
     def test_non_tuple_raises_exception(self):
         """
diff --git a/tests/urlpatterns_reverse/tests.py b/tests/urlpatterns_reverse/tests.py
index b2a6d83443..b4056ac7fa 100644
--- a/tests/urlpatterns_reverse/tests.py
+++ b/tests/urlpatterns_reverse/tests.py
@@ -17,6 +17,7 @@ from django.test.utils import override_settings
 from django.utils import six
 
 from . import urlconf_outer, middleware, views
+from .views import empty_view
 
 
 resolve_test_data = (
@@ -662,12 +663,20 @@ class ErroneousViewTests(TestCase):
 
 class ViewLoadingTests(TestCase):
     def test_view_loading(self):
+        self.assertEqual(get_callable('urlpatterns_reverse.views.empty_view'),
+                         empty_view)
+
+        # passing a callable should return the callable
+        self.assertEqual(get_callable(empty_view), empty_view)
+
+    def test_exceptions(self):
         # A missing view (identified by an AttributeError) should raise
         # ViewDoesNotExist, ...
-        six.assertRaisesRegex(self, ViewDoesNotExist, ".*View does not exist in.*",
-            get_callable,
-            'urlpatterns_reverse.views.i_should_not_exist')
+        six.assertRaisesRegex(self, ViewDoesNotExist,
+                              ".*View does not exist in.*",
+                              get_callable,
+                              'urlpatterns_reverse.views.i_should_not_exist')
         # ... but if the AttributeError is caused by something else don't
         # swallow it.
         self.assertRaises(AttributeError, get_callable,
-            'urlpatterns_reverse.views_broken.i_am_broken')
+                          'urlpatterns_reverse.views_broken.i_am_broken')