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

6 files changed, 47 insertions, 21 deletions

diff --git a/tests/regressiontests/cache/tests.py b/tests/regressiontests/cache/tests.py
index da4c9a8e7a..575021dc2b 100644
--- a/tests/regressiontests/cache/tests.py
+++ b/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)
 
-        # 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)
+        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')
+        finally:
+            restore_warnings_state(_warnings_state)
 
 class DBCacheTests(unittest.TestCase, BaseCacheTests):
     def setUp(self):
diff --git a/tests/regressiontests/context_processors/tests.py b/tests/regressiontests/context_processors/tests.py
index 2b5ddbe94c..5a89561bb6 100644
--- a/tests/regressiontests/context_processors/tests.py
+++ b/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):
         """
diff --git a/tests/regressiontests/csrf_tests/tests.py b/tests/regressiontests/csrf_tests/tests.py
index 7265b5b788..ea18d7d010 100644
--- a/tests/regressiontests/csrf_tests/tests.py
+++ b/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()
diff --git a/tests/regressiontests/syndication/tests.py b/tests/regressiontests/syndication/tests.py
index a69a454921..b9d77d9b0b 100644
--- a/tests/regressiontests/syndication/tests.py
+++ b/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):
         """
diff --git a/tests/regressiontests/templates/loaders.py b/tests/regressiontests/templates/loaders.py
index c59f838b4b..f0759ec2c6 100644
--- a/tests/regressiontests/templates/loaders.py
+++ b/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"
diff --git a/tests/regressiontests/test_utils/tests.py b/tests/regressiontests/test_utils/tests.py
index 995306e01d..2e55ba7718 100644
--- a/tests/regressiontests/test_utils/tests.py
+++ b/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