[1.5.x] Fixed #20922 -- Allowed customizing the serializer used by contrib.sessions

Added settings.SESSION_SERIALIZER which is the import path of a serializer
to use for sessions.

Thanks apollo13, carljm, shaib, akaariai, charettes, and dstufft for reviews.

Backport of b0ce6fe656 from master

2 files changed, 41 insertions, 19 deletions

diff --git a/tests/regressiontests/defer_regress/tests.py b/tests/regressiontests/defer_regress/tests.py
index d4d722035f..0bd0eedf01 100644
--- a/tests/regressiontests/defer_regress/tests.py
+++ b/tests/regressiontests/defer_regress/tests.py
@@ -7,6 +7,7 @@ from django.contrib.sessions.backends.db import SessionStore
 from django.db.models import Count
 from django.db.models.loading import cache
 from django.test import TestCase
+from django.test.utils import override_settings
 
 from .models import (ResolveThis, Item, RelatedItem, Child, Leaf, Proxy,
     SimpleItem, Feature, ItemAndSimpleItem, OneToOneItem, SpecialFeature)
@@ -80,24 +81,6 @@ class DeferRegressionTest(TestCase):
         self.assertEqual(results[0].child.name, "c1")
         self.assertEqual(results[0].second_child.name, "c2")
 
-        # Test for #12163 - Pickling error saving session with unsaved model
-        # instances.
-        SESSION_KEY = '2b1189a188b44ad18c35e1baac6ceead'
-
-        item = Item()
-        item._deferred = False
-        s = SessionStore(SESSION_KEY)
-        s.clear()
-        s["item"] = item
-        s.save()
-
-        s = SessionStore(SESSION_KEY)
-        s.modified = True
-        s.save()
-
-        i2 = s["item"]
-        self.assertFalse(i2._deferred)
-
         # Regression for #11936 - loading.get_models should not return deferred
         # models by default.
         klasses = sorted(
@@ -159,6 +142,27 @@ class DeferRegressionTest(TestCase):
             ]
         )
 
+    @override_settings(SESSION_SERIALIZER='django.contrib.sessions.serializers.PickleSerializer')
+    def test_ticket_12163(self):
+        # Test for #12163 - Pickling error saving session with unsaved model
+        # instances.
+        SESSION_KEY = '2b1189a188b44ad18c35e1baac6ceead'
+
+        item = Item()
+        item._deferred = False
+        s = SessionStore(SESSION_KEY)
+        s.clear()
+        s["item"] = item
+        s.save()
+
+        s = SessionStore(SESSION_KEY)
+        s.modified = True
+        s.save()
+
+        i2 = s["item"]
+        self.assertFalse(i2._deferred)
+
+    def test_ticket_16409(self):
         # Regression for #16409 - make sure defer() and only() work with annotate()
         self.assertIsInstance(list(SimpleItem.objects.annotate(Count('feature')).defer('name')), list)
         self.assertIsInstance(list(SimpleItem.objects.annotate(Count('feature')).only('name')), list)
diff --git a/tests/regressiontests/utils/module_loading.py b/tests/regressiontests/utils/module_loading.py
index 3fc92b0862..a9e3706bb9 100644
--- a/tests/regressiontests/utils/module_loading.py
+++ b/tests/regressiontests/utils/module_loading.py
@@ -3,9 +3,10 @@ import sys
 import imp
 from zipimport import zipimporter
 
+from django.core.exceptions import ImproperlyConfigured
 from django.utils import unittest
 from django.utils.importlib import import_module
-from django.utils.module_loading import module_has_submodule
+from django.utils.module_loading import import_by_path, module_has_submodule
 from django.utils._os import upath
 
 
@@ -103,6 +104,23 @@ class EggLoader(unittest.TestCase):
         self.assertFalse(module_has_submodule(egg_module, 'no_such_module'))
         self.assertRaises(ImportError, import_module, 'egg_module.sub1.sub2.no_such_module')
 
+
+class ModuleImportTestCase(unittest.TestCase):
+    def test_import_by_path(self):
+        cls = import_by_path(
+            'django.utils.module_loading.import_by_path')
+        self.assertEqual(cls, import_by_path)
+
+        # Test exceptions raised
+        for path in ('no_dots_in_path', 'unexistent.path',
+                'tests.regressiontests.utils.unexistent'):
+            self.assertRaises(ImproperlyConfigured, import_by_path, path)
+
+        with self.assertRaises(ImproperlyConfigured) as cm:
+            import_by_path('unexistent.module.path', error_prefix="Foo")
+        self.assertTrue(str(cm.exception).startswith('Foo'))
+
+
 class ProxyFinder(object):
     def __init__(self):
         self._cache = {}