Ticket #10808: 10808.diff

django/db/models/base.py

@@ -273 +273 @@
         # Now we're left with the unprocessed fields that *must* come from
         # keywords, or default.
 
+        # In the case of diamond inheritance, where B and C inherit from A, and
+        # D inherits from B and C, D will have "redundant" copies of each of
+        # A's fields. As we iterate through all the fields, the second time we
+        # see a field we run the risk of reassigning it the default value, so
+        # if a field has already been seen in assigned_fields, we ignore it.
+        assigned_fields = set()
         for field in fields_iter:
+            if field.attname in assigned_fields:
+                continue
             is_related_object = False
             # This slightly odd construct is so that we can access any
             # data-descriptor object (DeferredAttribute) without triggering its
@@ -311 +319 @@
                 setattr(self, field.name, rel_obj)
             else:
                 setattr(self, field.attname, val)
+            assigned_fields.add(field.attname)
 
         if kwargs:
             for prop in kwargs.keys():

tests/modeltests/model_inheritance/models.py

@@ -116 +116 @@
     def __unicode__(self):
         return u"%s the parking lot" % self.name
 
+#
+# Diamond inheritance test
+# 
+class FoodPlace(models.Model):
+    name = models.CharField(max_length=255)
+
+class Bar(FoodPlace):
+    pass
+
+class Pizzeria(FoodPlace):
+    pass
+
+class PizzeriaBar(Bar, Pizzeria):
+    pizza_bar_specific_field = models.CharField(max_length=255)
+
 __test__ = {'API_TESTS':"""
 # The Student and Worker models both have 'name' and 'age' fields on them and
 # inherit the __unicode__() method, just as with normal Python subclassing.
@@ -310 +325 @@
 3
 >>> settings.DEBUG = False
 
+# Test of diamond inheritance __init__. If B and C inherit from A, and D inherits from B and C, we should be able to use __init__ for D to properly set all the fields, regardless of the redundant copies of A's fields that D inherits from B and C.
+
+>>> p = PizzeriaBar(name="Mike's", pizza_bar_specific_field="Doodle")
+>>> p.name == "Mike's"
+True
+>>> p.pizza_bar_specific_field == "Doodle"
+True
 """}