[Django] #28823: Nested @override_settings on class and method do not work correctly

[Django]

#28823: Nested @override_settings on class and method do not work correctly
-----------------------------------------+------------------------
               Reporter:  Paolo D'Apice  |          Owner:  nobody
                   Type:  Bug            |         Status:  new
              Component:  Uncategorized  |        Version:  1.10
               Severity:  Normal         |       Keywords:
           Triage Stage:  Unreviewed     |      Has patch:  0
    Needs documentation:  0              |    Needs tests:  0
Patch needs improvement:  0              |  Easy pickings:  0
                  UI/UX:  0              |
-----------------------------------------+------------------------
 I am using the `@override_settings~ decorator to delete some settings
 during tests (accordint to the
 [https://docs.djangoproject.com/en/1.10/topics/testing/tools/#overriding-
 settings documentation]).

 I reproduced the problem with the following code:
 {{{#!python
 from django.test import TestCase, override_settings
 from django.conf import settings

 TEST_SETTINGS = {
     'MY_DATA': {
         'foo': 1,
         'bar': 2
     }
 }


 class Dummy:
     def foo(self):
         return settings.MY_DATA.get('foo')

     def bar(self):
         return settings.MY_DATA.get('bar')


 @override_settings(**TEST_SETTINGS)
 class SimpleTest(TestCase):
     def setUp(self):
         self.dummy = Dummy()

     def test_foobar(self):
         self.assertEqual(self.dummy.foo(), 1)
         self.assertEqual(self.dummy.bar(), 2)

     @override_settings()
     def test_delete_my_data(self):
         del settings.MY_DATA
         with self.assertRaises(AttributeError):
             self.dummy.foo()
         with self.assertRaises(AttributeError):
             self.dummy.bar()

     @override_settings()
     def test_delete_foo(self):
         del settings.MY_DATA['foo']
         self.assertIsNone(self.dummy.foo())
         self.assertEqual(self.dummy.bar(), 2)

     def test_foobar_again(self):
         self.assertEqual(self.dummy.foo(), 1)
         self.assertEqual(self.dummy.bar(), 2)
 }}}

 I expect all the test to pass, but instead I have some failures:

 {{{
 ..FF
 ======================================================================
 FAIL: test_foobar (api.tests.test_bug.SimpleTest)
 ----------------------------------------------------------------------
 Traceback (most recent call last):
   File "/Users/paolo/testproject/api/tests/test_bug.py", line 26, in
 test_foobar
     self.assertEqual(self.dummy.foo(), 1)
 AssertionError: None != 1

 ======================================================================
 FAIL: test_foobar_again (api.tests.test_bug.SimpleTest)
 ----------------------------------------------------------------------
 Traceback (most recent call last):
   File "/Users/paolo/testproject/api/tests/test_bug.py", line 44, in
 test_foobar_again
     self.assertEqual(self.dummy.foo(), 1)
 AssertionError: None != 1

 ----------------------------------------------------------------------
 Ran 4 tests in 0.045s

 FAILED (failures=2)
 }}}

 It seems to me that the overridden settings at method level are not
 cleared up after the test method runs, leaving the settings in a ''dirty''
 state.

-- 
Ticket URL: <https://code.djangoproject.com/ticket/28823>
Django <https://code.djangoproject.com/>
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