Fixed #14508 - test suite silences warnings.

Utility functions get_warnings_state and save_warnings_state have been added
to django.test.utils, and methods to django.test.TestCase for convenience.

The implementation is based on the catch_warnings context manager from
Python 2.6.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14526 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/auth/tests/auth_backends.py

@@ -154,13 +154,13 @@ class RowlevelBackendTest(TestCase):
         self.user1 = User.objects.create_user('test', 'test@example.com', 'test')
         self.user2 = User.objects.create_user('test2', 'test2@example.com', 'test')
         self.user3 = User.objects.create_user('test3', 'test3@example.com', 'test')
+        self.save_warnings_state()
         warnings.filterwarnings('ignore', category=DeprecationWarning,
                                 module='django.contrib.auth')
 
     def tearDown(self):
         settings.AUTHENTICATION_BACKENDS = self.curr_auth
-        warnings.resetwarnings()
-        warnings.simplefilter('ignore', PendingDeprecationWarning)
+        self.restore_warnings_state()
 
     def test_has_perm(self):
         self.assertEqual(self.user1.has_perm('perm', TestObj()), False)

django/contrib/messages/tests/base.py

@@ -51,6 +51,7 @@ class BaseTest(TestCase):
         self._message_storage = settings.MESSAGE_STORAGE
         settings.MESSAGE_STORAGE = '%s.%s' % (self.storage_class.__module__,
                                               self.storage_class.__name__)
+        self.save_warnings_state()
         warnings.filterwarnings('ignore', category=DeprecationWarning,
                                 module='django.contrib.auth.models')
 
@@ -63,8 +64,7 @@ class BaseTest(TestCase):
            self._template_context_processors
         settings.INSTALLED_APPS = self._installed_apps
         settings.MESSAGE_STORAGE = self._message_storage
-        warnings.resetwarnings()
-        warnings.simplefilter('ignore', PendingDeprecationWarning)
+        self.restore_warnings_state()
 
     def restore_setting(self, setting):
         if setting in self._remembered_settings:

django/test/testcases.py

@@ -11,6 +11,7 @@ from django.db import transaction, connection, connections, DEFAULT_DB_ALIAS
 from django.http import QueryDict
 from django.test import _doctest as doctest
 from django.test.client import Client
+from django.test.utils import get_warnings_state, restore_warnings_state
 from django.utils import simplejson, unittest as ut2
 from django.utils.encoding import smart_str
 from django.utils.functional import wraps
@@ -328,6 +329,19 @@ class TransactionTestCase(ut2.TestCase):
             settings.ROOT_URLCONF = self._old_root_urlconf
             clear_url_caches()
 
+    def save_warnings_state(self):
+        """
+        Saves the state of the warnings module
+        """
+        self._warnings_state = get_warnings_state()
+
+    def restore_warnings_state(self):
+        """
+        Restores the sate of the warnings module to the state
+        saved by save_warnings_state()
+        """
+        restore_warnings_state(self._warnings_state)
+
     def assertRedirects(self, response, expected_url, status_code=302,
                         target_status_code=200, host=None, msg_prefix=''):
         """Asserts that a response redirected to a specific URL, and that the

django/test/utils.py

@@ -1,6 +1,7 @@
 import sys
 import time
 import os
+import warnings
 from django.conf import settings
 from django.core import mail
 from django.core.mail.backends import locmem
@@ -46,6 +47,7 @@ class ContextList(list):
             return False
         return True
 
+
 def instrumented_test_render(self, context):
     """
     An instrumented Template render method, providing a signal
@@ -75,6 +77,7 @@ def setup_test_environment():
 
     deactivate()
 
+
 def teardown_test_environment():
     """Perform any global post-test teardown. This involves:
 
@@ -93,6 +96,25 @@ def teardown_test_environment():
 
     del mail.outbox
 
+
+def get_warnings_state():
+    """
+    Returns an object containing the state of the warnings module
+    """
+    # There is no public interface for doing this, but this implementation of
+    # get_warnings_state and restore_warnings_state appears to work on Python
+    # 2.4 to 2.7.
+    return warnings.filters[:]
+
+
+def restore_warnings_state(state):
+    """
+    Restores the state of the warnings module when passed an object that was
+    returned by get_warnings_state()
+    """
+    warnings.filters = state[:]
+
+
 def get_runner(settings):
     test_path = settings.TEST_RUNNER.split('.')
     # Allow for Python 2.5 relative paths

tests/regressiontests/cache/tests.py

@@ -15,6 +15,7 @@ from django.core.cache import get_cache
 from django.core.cache.backends.base import InvalidCacheBackendError, CacheKeyWarning
 from django.http import HttpResponse, HttpRequest
 from django.middleware.cache import FetchFromCacheMiddleware, UpdateCacheMiddleware
+from django.test.utils import get_warnings_state, restore_warnings_state
 from django.utils import translation
 from django.utils import unittest
 from django.utils.cache import patch_vary_headers, get_cache_key, learn_cache_key
@@ -379,21 +380,16 @@ class BaseCacheTests(object):
         # manager to test this warning nicely. Since we can't do that
         # yet, the cleanest option is to temporarily ask for
         # CacheKeyWarning to be raised as an exception.
+        _warnings_state = get_warnings_state()
         warnings.simplefilter("error", CacheKeyWarning)
 
+        try:
             # memcached does not allow whitespace or control characters in keys
             self.assertRaises(CacheKeyWarning, self.cache.set, 'key with spaces', 'value')
             # memcached limits key length to 250
             self.assertRaises(CacheKeyWarning, self.cache.set, 'a' * 251, 'value')
-
-        # The warnings module has no public API for getting the
-        # current list of warning filters, so we can't save that off
-        # and reset to the previous value, we have to globally reset
-        # it. The effect will be the same, as long as the Django test
-        # runner doesn't add any global warning filters (it currently
-        # does not).
-        warnings.resetwarnings()
-        warnings.simplefilter("ignore", PendingDeprecationWarning)
+        finally:
+            restore_warnings_state(_warnings_state)
 
 class DBCacheTests(unittest.TestCase, BaseCacheTests):
     def setUp(self):

tests/regressiontests/context_processors/tests.py

@@ -48,14 +48,14 @@ class AuthContextProcessorTests(TestCase):
     fixtures = ['context-processors-users.xml']
 
     def setUp(self):
+        self.save_warnings_state()
         warnings.filterwarnings('ignore', category=DeprecationWarning,
                                 module='django.contrib.auth.models')
         warnings.filterwarnings('ignore', category=DeprecationWarning,
                                 module='django.core.context_processors')
 
     def tearDown(self):
-        warnings.resetwarnings()
-        warnings.simplefilter('ignore', PendingDeprecationWarning)
+        self.restore_warnings_state()
 
     def test_session_not_accessed(self):
         """

tests/regressiontests/csrf_tests/tests.py

@@ -71,12 +71,12 @@ class CsrfMiddlewareTest(TestCase):
     _secret_key_for_session_test= "test"
 
     def setUp(self):
+        self.save_warnings_state()
         warnings.filterwarnings('ignore', category=DeprecationWarning,
                                 module='django.middleware.csrf')
 
     def tearDown(self):
-        warnings.resetwarnings()
-        warnings.simplefilter('ignore', PendingDeprecationWarning)
+        self.restore_warnings_state()
 
     def _get_GET_no_csrf_cookie_request(self):
         return TestingHttpRequest()

tests/regressiontests/syndication/tests.py

@@ -315,14 +315,14 @@ class DeprecatedSyndicationFeedTest(FeedTestCase):
     Tests for the deprecated API (feed() view and the feed_dict etc).
     """
     def setUp(self):
+        self.save_warnings_state()
         warnings.filterwarnings('ignore', category=DeprecationWarning,
                                 module='django.contrib.syndication.feeds')
         warnings.filterwarnings('ignore', category=DeprecationWarning,
                                 module='django.contrib.syndication.views')
 
     def tearDown(self):
-        warnings.resetwarnings()
-        warnings.simplefilter('ignore', PendingDeprecationWarning)
+        self.restore_warnings_state()
 
     def test_empty_feed_dict(self):
         """

tests/regressiontests/templates/loaders.py

@@ -20,6 +20,7 @@ from django.template import TemplateDoesNotExist, Context
 from django.template.loaders.eggs import load_template_source as lts_egg
 from django.template.loaders.eggs import Loader as EggLoader
 from django.template import loader
+from django.test.utils import get_warnings_state, restore_warnings_state
 from django.utils import unittest
 
 
@@ -68,13 +69,13 @@ class DeprecatedEggLoaderTest(unittest.TestCase):
         })
         self._old_installed_apps = settings.INSTALLED_APPS
         settings.INSTALLED_APPS = []
+        self._warnings_state = get_warnings_state()
         warnings.filterwarnings("ignore", category=DeprecationWarning,
                                 module='django.template.loaders.eggs')
 
     def tearDown(self):
         settings.INSTALLED_APPS = self._old_installed_apps
-        warnings.resetwarnings()
-        warnings.simplefilter("ignore", PendingDeprecationWarning)
+        restore_warnings_state(self._warnings_state)
 
     def test_existing(self):
         "A template can be loaded from an egg"

tests/regressiontests/test_utils/tests.py

@@ -26,6 +26,35 @@ class SkippingTestCase(TestCase):
         self.assertRaises(ValueError, test_func)
 
 
+class SaveRestoreWarningState(TestCase):
+
+    def test_save_restore_warnings_state(self):
+        """
+        Ensure save_warnings_state/restore_warnings_state work correctly.
+        """
+        # In reality this test could be satisfied by many broken implementations
+        # of save_warnings_state/restore_warnings_state (e.g. just
+        # warnings.resetwarnings()) , but it is difficult to test more.
+        import warnings
+        self.save_warnings_state()
+
+        class MyWarning(Warning):
+            pass
+
+        # Add a filter that causes an exception to be thrown, so we can catch it
+        warnings.simplefilter("error", MyWarning)
+        self.assertRaises(Warning, lambda: warnings.warn("warn", MyWarning))
+
+        # Now restore.
+        self.restore_warnings_state()
+        # After restoring, we shouldn't get an exception. But we don't want a
+        # warning printed either, so we have to silence the warning.
+        warnings.simplefilter("ignore", MyWarning)
+        warnings.warn("warn", MyWarning)
+
+        # Remove the filter we just added.
+        self.restore_warnings_state()
+
 __test__ = {"API_TEST": r"""
 # Some checks of the doctest output normalizer.
 # Standard doctests do fairly