Opening cached record fails in admin

[nickzam]

I experienced some problems in admin site when I tried to use django-caching for my app. ( TypeError: can't pickle instancemethod objects ) when tried to view cached model record.

All works like a charm, but opening cached record in admin site fails :(

Object that caching tried to cache and fails is CachingManyToManyField with values [7L, 11L].

Latest SVN Django 1.1 beta + mysql4.23 + python2.6 + memcache on WinXP sp3 under Django built-in dev server.
See http://paste.pocoo.org/show/119491/

Traceback (most recent call last):
File "d:\python26\Lib\site-packages\django\core\servers\basehttp.py", line 636, in call
return self.application(environ, start_response)
File "D:\Python26\lib\site-packages\django\core\handlers\wsgi.py", line 241, in call
response = self.get_response(request)
File "D:\Python26\Lib\site-packages\django\core\handlers\base.py", line 134, in get_response
return self.handle_uncaught_exception(request, resolver, exc_info)
File "D:\Python26\Lib\site-packages\django\core\handlers\base.py", line 154, in handle_uncaught_exception
return debug.technical_500_response(request, _exc_info)
File "D:\Python26\Lib\site-packages\django\core\handlers\base.py", line 92, in get_response
response = callback(request, *callback_args, *_callback_kwargs)
File "d:\python26\Lib\site-packages\django\contrib\admin\sites.py", line 480, in root
return self.model_page(request, _url.split('/', 2))
File "D:\Python26\lib\site-packages\django\views\decorators\cache.py", line 44, in _wrapped_view_func
response = view_func(request, *args, *_kwargs)
File "d:\python26\Lib\site-packages\django\contrib\admin\sites.py", line 499, in model_page
return admin_obj(request, rest_of_url)
File "d:\python26\Lib\site-packages\django\contrib\admin\options.py", line 1094, in call
return self.change_view(request, unquote(url))
File "D:\Python26\lib\site-packages\django\db\transaction.py", line 240, in _commit_on_success
res = func(_args, *_kw)
File "d:\python26\Lib\site-packages\django\contrib\admin\options.py", line 839, in change_view
form = ModelForm(instance=obj)
File "D:\Python26\Lib\site-packages\django\forms\models.py", line 222, in init
object_data = model_to_dict(instance, opts.fields, opts.exclude)
File "D:\Python26\Lib\site-packages\django\forms\models.py", line 140, in model_to_dict
data[f.name] = [obj.pk for obj in f.value_from_object(instance)]
File "d:\python26\Lib\site-packages\django\db\models\fields\related.py", line 940, in value_from_object
return getattr(obj, self.attname).all()
File "D:\Python26\Scripts\gurt\apps\caching\fields.py", line 73, in all
cache.add(key, pk_list, CACHE_DURATION)
File "D:\Python26\Scripts\gurt\apps\caching\cache.py", line 16, in add
return self._cache.add(smart_str(key), value, timeout, min_compress_len)
File "build\bdist.win32\egg\memcache.py", line 443, in add
return self._set("add", key, val, time, min_compress_len)
File "build\bdist.win32\egg\memcache.py", line 681, in _set
store_info = self._val_to_store_info(val, min_compress_len)
File "build\bdist.win32\egg\memcache.py", line 654, in _val_to_store_info
pickler.dump(val)
File "d:\Python26\Lib\copy_reg.py", line 70, in _reduce_ex
raise TypeError, "can't pickle %s objects" % base.name
TypeError: can't pickle instancemethod objects

[mmalone]

Strange. Seems an instance method is being sent to the cache somehow, but that shouldn't happen since the code only caches a list of primary keys. Any info on how I can reproduce it?

[nickzam]

I've created a sample quick and dirty error project based on your django-caching here: http://bitbucket.org/zam/django-caching-errorexample/
Go to http://127.0.0.1:8000/admin/ (login: admin, pass:123) and try to add new article. It will fail when you press Save button.
I think that problem was related to my models, but it seems to be related to the django built-in admin contrib. So you can ignore _errormodels.py - it's almost the same as yours (one many2many link to other table).

Here is paste for this error:
http://dpaste.com/50941/

Thank you for support.

[mmalone]

Fixed... thanks to the three forkers who figured this one out (matclayton, anarcher, and baratrion).