[1.7.x] Fixed #23934 -- Fixed regression in admin views obj parameter.

Backport of 0623f4dea4 from master

tests/admin_views/tests.py

@@ -5056,3 +5056,51 @@ class AdminGenericRelationTests(TestCase):
             validator.validate_list_filter(GenericFKAdmin, Plot)
         except ImproperlyConfigured:
             self.fail("Couldn't validate a GenericRelation -> FK path in ModelAdmin.list_filter")
+
+
+@override_settings(
+    PASSWORD_HASHERS=('django.contrib.auth.hashers.SHA1PasswordHasher',),
+    ROOT_URLCONF="admin_views.urls",
+)
+class GetFormsetsWithInlinesArgumentTest(TestCase):
+    """
+    #23934 - When adding a new model instance in the admin, the 'obj' argument
+    of get_formsets_with_inlines() should be None. When changing, it should be
+    equal to the existing model instance.
+    The GetFormsetsArgumentCheckingAdmin ModelAdmin throws an exception
+    if obj is not None during add_view or obj is None during change_view.
+    """
+    fixtures = ['admin-views-users.xml']
+
+    def setUp(self):
+        self.client.login(username='super', password='secret')
+
+    def test_explicitly_provided_pk(self):
+        post_data = {'name': '1'}
+        try:
+            response = self.client.post('/test_admin/admin/admin_views/explicitlyprovidedpk/add/', post_data)
+        except Exception as e:
+            self.fail(e)
+        self.assertEqual(response.status_code, 302)
+
+        post_data = {'name': '2'}
+        try:
+            response = self.client.post('/test_admin/admin/admin_views/explicitlyprovidedpk/1/', post_data)
+        except Exception as e:
+            self.fail(e)
+        self.assertEqual(response.status_code, 302)
+
+    def test_implicitly_generated_pk(self):
+        post_data = {'name': '1'}
+        try:
+            response = self.client.post('/test_admin/admin/admin_views/implicitlygeneratedpk/add/', post_data)
+        except Exception as e:
+            self.fail(e)
+        self.assertEqual(response.status_code, 302)
+
+        post_data = {'name': '2'}
+        try:
+            response = self.client.post('/test_admin/admin/admin_views/implicitlygeneratedpk/1/', post_data)
+        except Exception as e:
+            self.fail(e)
+        self.assertEqual(response.status_code, 302)