#21733: @python_2_unicode_compatible causes infinite recursion when module
imported
more than once
----------------------------+-------------------------
Reporter: ntucker | Owner: nobody
Type: Bug | Status: new
Component: Utilities | Version: 1.6
Severity: Normal | Keywords: python2.7.3
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 1 | UI/UX: 0
----------------------------+-------------------------
Sometimes a module that uses @python_2_unicode_compatible is imported
multiple times. Possibly because a different pathname is used to import
it. When this occurs, it makes __unicode__ be the __str__ function that
was originally assigned, which calls __unicode__. So anytime __unicode__
is called on the object, there is infinite recursion.
A simple check whether the __str__ function has already been assigned will
prevent setting __unicode__ to the provided recursive function. This will
also guard against other cases of multiple @python_2_unicode_compatible
calls.
{{{
class _STR(object):
def __call__(self, obj):
return self.__unicode__().encode('utf-8')
_str = _STR()
def python_2_unicode_compatible(klass):
"""
A decorator that defines __unicode__ and __str__ methods under Python 2.
Under Python 3 it does nothing.
To support Python 2 and 3 with a single code base, define a __str__ method
returning text and apply this decorator to the class.
"""
if six.PY2:
if '__str__' not in klass.__dict__:
raise ValueError("@python_2_unicode_compatible cannot be
applied "
"to %s because it doesn't define __str__()."
%
klass.__name__)
# this was already applied once
if klass.__str__ == _str:
return klass
klass.__unicode__ = klass.__str__
klass.__str__ = _str
return klass
}}}
I will provide patch if this is accepted. Above is example code.
--
Ticket URL: <https://code.djangoproject.com/ticket/21733>
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