Fixed django#18590 - Reverted Python 2.4 workaround for Model pickling

Revert of 08d521e. Refs django#10547, django#12121. Thanks Michal Petrucha for the report.

Author: claudep

django/db/models/base.py

@@ -16,7 +16,7 @@
 from django.db import (router, transaction, DatabaseError,
  DEFAULT_DB_ALIAS)
 from django.db.models.query import Q
-from django.db.models.query_utils import DeferredAttribute
+from django.db.models.query_utils import DeferredAttribute, deferred_class_factory
 from django.db.models.deletion import Collector
 from django.db.models.options import Options
 from django.db.models import signals
@@ -400,25 +400,16 @@ def __reduce__(self):
  need to do things manually, as they're dynamically created classes and
  only module-level classes can be pickled by the default path.
  """
+ if not self._deferred:
+ return super(Model, self).__reduce__()
  data = self.__dict__
- model = self.__class__
- # The obvious thing to do here is to invoke super().__reduce__()
- # for the non-deferred case. Don't do that.
- # On Python 2.4, there is something weird with __reduce__,
- # and as a result, the super call will cause an infinite recursion.
- # See #10547 and #12121.
  defers = []
- if self._deferred:
- from django.db.models.query_utils import deferred_class_factory
- factory = deferred_class_factory
- for field in self._meta.fields:
- if isinstance(self.__class__.__dict__.get(field.attname),
- DeferredAttribute):
- defers.append(field.attname)
- model = self._meta.proxy_for_model
- else:
- factory = simple_class_factory
- return (model_unpickle, (model, defers, factory), data)
+ for field in self._meta.fields:
+ if isinstance(self.__class__.__dict__.get(field.attname),
+ DeferredAttribute):
+ defers.append(field.attname)
+ model = self._meta.proxy_for_model
+ return (model_unpickle, (model, defers), data)
 
  def _get_pk_val(self, meta=None):
  if not meta:
@@ -926,20 +917,11 @@ def get_absolute_url(opts, func, self, *args, **kwargs):
 class Empty(object):
  pass
 
-def simple_class_factory(model, attrs):
- """Used to unpickle Models without deferred fields.
-
- We need to do this the hard way, rather than just using
- the default __reduce__ implementation, because of a
- __deepcopy__ problem in Python 2.4
- """
- return model
-
-def model_unpickle(model, attrs, factory):
+def model_unpickle(model, attrs):
  """
  Used to unpickle Model subclasses with deferred fields.
  """
- cls = factory(model, attrs)
+ cls = deferred_class_factory(model, attrs)
  return cls.__new__(cls)
 model_unpickle.__safe_for_unpickle__ = True