Ticket #19688: 0001-Fixed-19688-Allow-model-subclassing-with-a-custom-me.patch

django/db/models/base.py

@@ -60 +60 @@
         super_new = super(ModelBase, cls).__new__
         # six.with_metaclass() inserts an extra class called 'NewBase' in the
         # inheritance tree: Model -> NewBase -> object. Ignore this class.
+        if (name == 'NewBase' and
+            any(isinstance(b, ModelBase) for b in bases)):
+            return super_new(cls, name, bases, attrs)
         parents = [b for b in bases if isinstance(b, ModelBase) and
                 not (b.__name__ == 'NewBase' and b.__mro__ == (b, object))]
         if not parents:

new file tests/modeltests/base/models.py

@@ +1 @@
+from django.db import models
+
+
+class CustomBaseModel(models.base.ModelBase):
+    pass
+ No newline at end of file

new file tests/modeltests/base/tests.py

@@ +1 @@
+from __future__ import unicode_literals
+
+from django.db import models
+from django.test.testcases import SimpleTestCase
+from django.utils import six
+from django.utils.unittest.case import skipIf
+
+from .models import CustomBaseModel
+
+
+class CustomBaseTest(SimpleTestCase):
+    @skipIf(six.PY3, 'test metaclass definition under Python 2')
+    def test_py2_custom_base(self):
+        """
+        Make sure models.Model can be subclassed with a valid custom base
+        using __metaclass__
+        """
+        try:
+            class PY2CustomModel(models.Model):
+                __metaclass__ = CustomBaseModel
+        except Exception:
+            self.fail("models.Model couldn't be subclassed with a valid "
+                      "custom base using __metaclass__.")
+
+    def test_six_custom_base(self):
+        """
+        Make sure models.Model can be subclassed with a valid custom base
+        using `six.with_metaclass`.
+        """
+        try:
+            class SixCustomModel(six.with_metaclass(CustomBaseModel,
+                                                 models.Model)):
+                pass
+        except Exception:
+            self.fail("models.Model couldn't be subclassed with a valid "
+                      "custom base using `six.with_metaclass`.")
+ No newline at end of file