model_split: Fixed #19236 - fixed error for abstract models with a split method

django/db/models/fields/related.py

@@ -54,14 +54,16 @@ class MyModel(Model):
 
     else:
         # Look for an "app.Model" relation
-        try:
-            app_label, model_name = relation.split(".")
-        except ValueError:
-            # If we can't split, assume a model in current app
-            app_label = cls._meta.app_label
-            model_name = relation
-        except AttributeError:
-            # If it doesn't have a split it's actually a model class
+
+        if isinstance(relation, six.string_types):
+            try:
+                app_label, model_name = relation.split(".")
+            except ValueError:
+                # If we can't split, assume a model in current app
+                app_label = cls._meta.app_label
+                model_name = relation
+        else:
+            # it's actually a model class
             app_label = relation._meta.app_label
             model_name = relation._meta.object_name
 

tests/regressiontests/m2m_regress/models.py

@@ -61,3 +61,20 @@ class Worksheet(models.Model):
 class User(models.Model):
     name = models.CharField(max_length=30)
     friends = models.ManyToManyField(auth.User)
+
+
+class BadModelWithSplit(models.Model):
+    name = models.CharField(max_length=1)
+
+    def split(self):
+        raise RuntimeError('split should not be called')
+
+    class Meta:
+        abstract = True
+
+
+class RegressionModelSplit(BadModelWithSplit):
+    """
+    Model with a split method should not cause an error in add_lazy_relation
+    """
+    others = models.ManyToManyField('self')

tests/regressiontests/m2m_regress/tests.py

@@ -5,7 +5,7 @@
 from django.utils import six
 
 from .models import (SelfRefer, Tag, TagCollection, Entry, SelfReferChild,
-    SelfReferChildSibling, Worksheet)
+    SelfReferChildSibling, Worksheet, RegressionModelSplit)
 
 
 class M2MRegressionTests(TestCase):
@@ -90,3 +90,9 @@ def test_manager_class_caching(self):
         # Get same manager for different instances
         self.assertTrue(e1.topics.__class__ is e2.topics.__class__)
         self.assertTrue(t1.entry_set.__class__ is t2.entry_set.__class__)
+
+    def test_m2m_abstract_split(self):
+        # Regression for #19236 - an abstract class with a 'split' method
+        # causes a TypeError in add_lazy_relation
+        m1 = RegressionModelSplit(name='1')
+        m1.save()