diff --git a/django/utils/functional.py b/django/utils/functional.py index 1dcbd55664..839dd4ef85 100644 --- a/django/utils/functional.py +++ b/django/utils/functional.py @@ -5,6 +5,12 @@ import sys from django.utils import six +try: + import copyreg +except ImportError: + import copy_reg as copyreg + + # You can't trivially replace this `functools.partial` because this binds to # classes and returns bound instances, whereas functools.partial (on CPython) # is a type and its instances don't bind. @@ -294,15 +300,23 @@ class SimpleLazyObject(LazyObject): self._setup() return self._wrapped.__dict__ - # Python 3.3 will call __reduce__ when pickling; these methods are needed - # to serialize and deserialize correctly. They are not called in earlier - # versions of Python. + # Python 3.3 will call __reduce__ when pickling; this method is needed + # to serialize and deserialize correctly. @classmethod def __newobj__(cls, *args): return cls.__new__(cls, *args) - def __reduce__(self): - return (self.__newobj__, (self.__class__,), self.__getstate__()) + def __reduce_ex__(self, proto): + if proto >= 2: + # On Py3, since the default protocol is 3, pickle uses the + # ``__newobj__`` method (& more efficient opcodes) for writing. + return (self.__newobj__, (self.__class__,), self.__getstate__()) + else: + # On Py2, the default protocol is 0 (for back-compat) & the above + # code fails miserably (see regression test). Instead, we return + # exactly what's returned if there's no ``__reduce__`` method at + # all. + return (copyreg._reconstructor, (self.__class__, object, None), self.__getstate__()) # Need to pretend to be the wrapped class, for the sake of objects that care # about this (especially in equality tests) diff --git a/tests/regressiontests/utils/simplelazyobject.py b/tests/regressiontests/utils/simplelazyobject.py index 3f81e8f608..2dd382cf04 100644 --- a/tests/regressiontests/utils/simplelazyobject.py +++ b/tests/regressiontests/utils/simplelazyobject.py @@ -121,3 +121,25 @@ class TestUtilsSimpleLazyObject(TestCase): self.assertEqual(unpickled, x) self.assertEqual(six.text_type(unpickled), six.text_type(x)) self.assertEqual(unpickled.name, x.name) + + def test_pickle_py2_regression(self): + from django.contrib.auth.models import User + + # See ticket #20212 + user = User.objects.create_user('johndoe', 'john@example.com', 'pass') + x = SimpleLazyObject(lambda: user) + + # This would fail with "TypeError: can't pickle instancemethod objects", + # only on Python 2.X. + pickled = pickle.dumps(x) + + # Try the variant protocol levels. + pickled = pickle.dumps(x, 0) + pickled = pickle.dumps(x, 1) + pickled = pickle.dumps(x, 2) + + if not six.PY3: + import cPickle + + # This would fail with "TypeError: expected string or Unicode object, NoneType found". + pickled = cPickle.dumps(x)