Fixed #31802 -- Added system check for non-integer SITE_ID.

django/contrib/sites/apps.py

@@ -1,4 +1,6 @@
 from django.apps import AppConfig
+from django.contrib.sites.checks import check_site_id
+from django.core import checks
 from django.db.models.signals import post_migrate
 from django.utils.translation import gettext_lazy as _
 
@@ -11,3 +13,4 @@ class SitesConfig(AppConfig):
 
     def ready(self):
         post_migrate.connect(create_default_site, sender=self)
+        checks.register(check_site_id, checks.Tags.sites)

django/contrib/sites/checks.py

@@ -0,0 +1,13 @@
+from django.conf import settings
+from django.core.checks import Error
+
+
+def check_site_id(app_configs, **kwargs):
+    if (
+        hasattr(settings, 'SITE_ID') and
+        not isinstance(settings.SITE_ID, (type(None), int))
+    ):
+        return [
+            Error('The SITE_ID setting must be an integer', id='sites.E101'),
+        ]
+    return []

django/core/checks/registry.py

@@ -15,6 +15,7 @@ class Tags:
     models = 'models'
     security = 'security'
     signals = 'signals'
+    sites = 'sites'
     staticfiles = 'staticfiles'
     templates = 'templates'
     translation = 'translation'

docs/ref/checks.txt

@@ -85,6 +85,7 @@ Django's system checks are organized using the following tags:
 * ``models``: Checks of model, field, and manager definitions.
 * ``security``: Checks security related configuration.
 * ``signals``: Checks on signal declarations and handler registrations.
+* ``sites``: Checks :mod:`django.contrib.sites` configuration.
 * ``staticfiles``: Checks :mod:`django.contrib.staticfiles` configuration.
 * ``templates``: Checks template related configuration.
 * ``translation``: Checks translation related configuration.
@@ -101,6 +102,10 @@ Some checks may be registered with multiple tags.
     The ``database`` checks are now run only for database aliases specified
     using the :option:`check --database` option.
 
+.. versionchanged:: 3.2
+
+    The ``sites`` tag was added.
+
 Core system checks
 ==================
 
@@ -813,6 +818,11 @@ The following checks are performed on any model using a
 * **sites.E002**: ``CurrentSiteManager`` cannot use ``<field>`` as it is not a
   foreign key or a many-to-many field.
 
+The following checks verify that :mod:`django.contrib.sites` is correctly
+configured:
+
+* **sites.E101**: The :setting:`SITE_ID` setting must be an integer.
+
 ``staticfiles``
 ---------------
 

tests/sites_tests/tests.py

@@ -2,11 +2,13 @@ from django.apps import apps
 from django.apps.registry import Apps
 from django.conf import settings
 from django.contrib.sites import models
+from django.contrib.sites.checks import check_site_id
 from django.contrib.sites.management import create_default_site
 from django.contrib.sites.middleware import CurrentSiteMiddleware
 from django.contrib.sites.models import Site, clear_site_cache
 from django.contrib.sites.requests import RequestSite
 from django.contrib.sites.shortcuts import get_current_site
+from django.core import checks
 from django.core.exceptions import ObjectDoesNotExist, ValidationError
 from django.db.models.signals import post_migrate
 from django.http import HttpRequest, HttpResponse
@@ -82,7 +84,7 @@ class SitesFrameworkTests(TestCase):
             self.assertIsInstance(site, RequestSite)
             self.assertEqual(site.name, "example.com")
 
-    @override_settings(SITE_ID='', ALLOWED_HOSTS=['example.com'])
+    @override_settings(SITE_ID=None, ALLOWED_HOSTS=['example.com'])
     def test_get_current_site_no_site_id(self):
         request = HttpRequest()
         request.META = {
@@ -93,7 +95,7 @@ class SitesFrameworkTests(TestCase):
         site = get_current_site(request)
         self.assertEqual(site.name, "example.com")
 
-    @override_settings(SITE_ID='', ALLOWED_HOSTS=['example.com'])
+    @override_settings(SITE_ID=None, ALLOWED_HOSTS=['example.com'])
     def test_get_current_site_host_with_trailing_dot(self):
         """
         The site is matched if the name in the request has a trailing dot.
@@ -106,7 +108,7 @@ class SitesFrameworkTests(TestCase):
         site = get_current_site(request)
         self.assertEqual(site.name, 'example.com')
 
-    @override_settings(SITE_ID='', ALLOWED_HOSTS=['example.com', 'example.net'])
+    @override_settings(SITE_ID=None, ALLOWED_HOSTS=['example.com', 'example.net'])
     def test_get_current_site_no_site_id_and_handle_port_fallback(self):
         request = HttpRequest()
         s1 = self.site
@@ -167,7 +169,7 @@ class SitesFrameworkTests(TestCase):
         expected_cache = {self.site.id: self.site}
         self.assertEqual(models.SITE_CACHE, expected_cache)
 
-        with self.settings(SITE_ID=''):
+        with self.settings(SITE_ID=None):
             get_current_site(request)
 
         expected_cache.update({self.site.domain: self.site})
@@ -176,7 +178,7 @@ class SitesFrameworkTests(TestCase):
         clear_site_cache(Site, instance=self.site, using='default')
         self.assertEqual(models.SITE_CACHE, {})
 
-    @override_settings(SITE_ID='', ALLOWED_HOSTS=['example2.com'])
+    @override_settings(SITE_ID=None, ALLOWED_HOSTS=['example2.com'])
     def test_clear_site_cache_domain(self):
         site = Site.objects.create(name='example2.com', domain='example2.com')
         request = HttpRequest()
@@ -205,6 +207,20 @@ class SitesFrameworkTests(TestCase):
         self.assertEqual(Site.objects.get_by_natural_key(self.site.domain), self.site)
         self.assertEqual(self.site.natural_key(), (self.site.domain,))
 
+    @override_settings(SITE_ID='1')
+    def test_check_site_id(self):
+        self.assertEqual(check_site_id(None), [
+            checks.Error(
+                msg='The SITE_ID setting must be an integer',
+                id='sites.E101',
+            ),
+        ])
+
+    def test_valid_site_id(self):
+        for site_id in [1, None]:
+            with self.subTest(site_id=site_id), self.settings(SITE_ID=site_id):
+                self.assertEqual(check_site_id(None), [])
+
 
 @override_settings(ALLOWED_HOSTS=['example.com'])
 class RequestSiteTests(SimpleTestCase):