Ticket #16759: 16759.diff

django/contrib/contenttypes/generic.py

@@ -1 +1 @@
 """
 Classes allowing "generic" relations through ContentType and object-id fields.
 """
-
+import copy
 from functools import partial
 from django.core.exceptions import ObjectDoesNotExist
 from django.db import connection
@@ -25 +25 @@
         self.ct_field = ct_field
         self.fk_field = fk_field
 
+    def clone(self):
+        return copy.copy(self)
+
     def contribute_to_class(self, cls, name):
         self.name = name
         self.model = cls

django/db/models/base.py

@@ -165 +165 @@
             else:
                 # .. and abstract ones.
                 for field in parent_fields:
-                    new_class.add_to_class(field.name, copy.deepcopy(field))
+                    new_class.add_to_class(field.name, field.clone())
 
                 # Pass any non-abstract parent classes onto child.
                 new_class._meta.parents.update(base._meta.parents)
@@ -186 +186 @@
                                      'with field of similar name from '\
                                      'abstract base class %r' % \
                                         (field.name, name, base.__name__))
-                new_class.add_to_class(field.name, copy.deepcopy(field))
+                new_class.add_to_class(field.name, field.clone())
 
         if abstract:
             # Abstract base models can't be instantiated and don't appear in

django/db/models/fields/__init__.py

@@ -123 +123 @@
         return cmp(self.creation_counter, other.creation_counter)
 
     def __deepcopy__(self, memodict):
-        # We don't have to deepcopy very much here, since most things are not
+        # Outside of model initialization, a field instance is immutable by
+        # convention. In model initialiazation you should not use deepcopy to
+        # get a new instance similar to another one. Use clone instead.
+        return self
+
+    def clone(self):
+        # We don't have to clone very much here, since most things are not
         # intended to be altered after initial creation.
         obj = copy.copy(self)
         if self.rel:
             obj.rel = copy.copy(self.rel)
-        memodict[id(self)] = obj
         return obj
 
     def to_python(self, value):

django/db/models/options.py

@@ -54 +54 @@
         # from *other* models. Needed for some admin checks. Internal use only.
         self.related_fkey_lookups = []
 
+    def __deepcopy__(self, memo):
+        return self
+
     def contribute_to_class(self, cls, name):
         from django.db import connection
         from django.db.backends.util import truncate_name