Python Crash with ORM Inheritance

[peterbraden@…]

This bug causes a reproducible crash in the python interpreter [python issue5014] on my system, so I can't give a specific traceback, but I believe that an infinite recursion is generated when I try and use the db_column in a TextField.

Basically, I'm modifying one of my models to allow inheritance of a field so rather than keep the existing field which cannot be overridden with a function in the subclass, I'm creating a property to access the field - ie:

class Foo(model):
  _bar = TextField(db_column = 'bar')

  bar = property(lambda x: x.bar)

class Bla(Foo):
  @property
  def bar(self): whatever

I think the db_column = 'bar' causes problems as there is a Foo.bar attribute so somewhere in the model this is screwing things up by making an infinite loop which for some reason is breaking the python runtime.

Reproducible with revision 9787

[Alex Gaynor]

edited for readability, please use the preview feature :)

[(none)]

Milestone post-1.0 deleted

[Alex Gaynor]

This is working fine for me:

In [1]: from django.db import models

In [2]: class Foo(models.Model):
   ...:     _bar = models.TextField(db_column='bar')
   ...:     bar = property(lambda self: self._bar)
   ...:     
   ...:     
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)

/home/alex/<ipython console> in <module>()

/usr/lib/python2.5/site-packages/django/db/models/base.pyc in __new__(cls, name, bases, attrs)
     49             # For 'django.contrib.sites.models', this would be 'sites'.
     50             model_module = sys.modules[new_class.__module__]
---> 51             kwargs = {"app_label": model_module.__name__.split('.')[-2]}
     52         else:
     53             kwargs = {}

IndexError: list index out of range

In [3]: class Foo(models.Model):
    _bar = models.TextField(db_column='bar')
    bar = property(lambda self: self._bar)
   ...:     class Meta:
   ...:         app_label = ''
   ...:         
   ...:         

In [6]: class Bla(Foo):
   ...:     bar = pro
projects/alexs_language  projects/euler           property
projects/chatlog         projects/hoogstraten     
projects/election_sim    projects/pinax           
   ...:     bar = property(lambda self: "a")
   ...:     
   ...:     
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)

/home/alex/<ipython console> in <module>()

/usr/lib/python2.5/site-packages/django/db/models/base.pyc in __new__(cls, name, bases, attrs)
     49             # For 'django.contrib.sites.models', this would be 'sites'.
     50             model_module = sys.modules[new_class.__module__]
---> 51             kwargs = {"app_label": model_module.__name__.split('.')[-2]}
     52         else:
     53             kwargs = {}

IndexError: list index out of range

In [7]: class Bla(Foo):
    bar = property(lambda self: "a")
   ...:     class Meta:
   ...:         app_label = ''
   ...:         
   ...:         

In [9]: Foo.bar
Out[9]: <property object at 0x8d2c5cc>

In [10]: Foo().bar
Out[10]: ''

In [11]: Foo(_bar='a').bar
Out[11]: 'a'

In [12]: Bla().bar
Out[12]: 'a'

In [13]: Bla(_bar="f").bar
Out[13]: 'a'

There's some debugging cruft in there because I was working from the shell, but it seems to work fine,