[1.8.x] Fixed #24332 -- Fixed contrib.sites create_default_site() when 'default' DATABASES is empty.

Backport of e8cf4f8abe from master

django/contrib/sites/management.py

@@ -17,7 +17,7 @@ def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT
     if not router.allow_migrate(using, Site):
         return
 
-    if not Site.objects.exists():
+    if not Site.objects.using(using).exists():
         # The default settings set SITE_ID = 1, and some tests in Django's test
         # suite rely on this value. However, if database sequences are reused
         # (e.g. in the test suite after flush/syncdb), it isn't guaranteed that

django/contrib/sites/models.py

@@ -112,12 +112,13 @@ def clear_site_cache(sender, **kwargs):
     Clears the cache (if primed) each time a site is saved or deleted
     """
     instance = kwargs['instance']
+    using = kwargs['using']
     try:
         del SITE_CACHE[instance.pk]
     except KeyError:
         pass
     try:
-        del SITE_CACHE[Site.objects.get(pk=instance.pk).domain]
+        del SITE_CACHE[Site.objects.using(using).get(pk=instance.pk).domain]
     except (KeyError, Site.DoesNotExist):
         pass
 pre_save.connect(clear_site_cache, sender=Site)

docs/releases/1.7.5.txt

@@ -16,3 +16,6 @@ Bugfixes
 
 * Fixed a regression that prevented custom fields inheriting from
   ``ManyToManyField`` from being recognized in migrations (:ticket:`24236`).
+
+* Fixed crash in ``contrib.sites`` migrations when a default database isn't
+  used (:ticket:`24332`).

tests/sites_tests/tests.py

@@ -17,6 +17,7 @@ from django.test.utils import captured_stdout
 
 @modify_settings(INSTALLED_APPS={'append': 'django.contrib.sites'})
 class SitesFrameworkTests(TestCase):
+    multi_db = True
 
     def setUp(self):
         self.site = Site(
@@ -112,7 +113,26 @@ class SitesFrameworkTests(TestCase):
         expected_cache.update({self.site.domain: self.site})
         self.assertEqual(models.SITE_CACHE, expected_cache)
 
-        clear_site_cache(Site, instance=self.site)
+        clear_site_cache(Site, instance=self.site, using='default')
+        self.assertEqual(models.SITE_CACHE, {})
+
+    @override_settings(SITE_ID='')
+    def test_clear_site_cache_domain(self):
+        site = Site.objects.create(name='example2.com', domain='example2.com')
+        request = HttpRequest()
+        request.META = {
+            "SERVER_NAME": "example2.com",
+            "SERVER_PORT": "80",
+        }
+        get_current_site(request)  # prime the models.SITE_CACHE
+        expected_cache = {site.domain: site}
+        self.assertEqual(models.SITE_CACHE, expected_cache)
+
+        # Site exists in 'default' database so using='other' shouldn't clear.
+        clear_site_cache(Site, instance=site, using='other')
+        self.assertEqual(models.SITE_CACHE, expected_cache)
+        # using='default' should clear.
+        clear_site_cache(Site, instance=site, using='default')
         self.assertEqual(models.SITE_CACHE, {})
 
 
@@ -146,7 +166,7 @@ class CreateDefaultSiteTests(TestCase):
         self.assertEqual("", stdout.getvalue())
 
     @override_settings(DATABASE_ROUTERS=[JustOtherRouter()])
-    def test_multi_db(self):
+    def test_multi_db_with_router(self):
         """
         #16353, #16828 - The default site creation should respect db routing.
         """
@@ -155,6 +175,12 @@ class CreateDefaultSiteTests(TestCase):
         self.assertFalse(Site.objects.using('default').exists())
         self.assertTrue(Site.objects.using('other').exists())
 
+    def test_multi_db(self):
+        create_default_site(self.app_config, using='default', verbosity=0)
+        create_default_site(self.app_config, using='other', verbosity=0)
+        self.assertTrue(Site.objects.using('default').exists())
+        self.assertTrue(Site.objects.using('other').exists())
+
     def test_save_another(self):
         """
         #17415 - Another site can be created right after the default one.