PicklingError: Can't pickle <class 'django.template.SimpleNode'>: attribute lookup django.template.SimpleNode failed

[Simon Law <simon@…>]

Code to reproduce:

import pickle
from django import template
t = template.Template("{% load adminmedia %}{% admin_media_prefix %}")
p = pickle.dumps(t)
print pickle.loads(p).render(template.Context({}))

Expected result:

u'/admin/media/'

Bug:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/pickle.py", line 1366, in dumps
    Pickler(file, protocol).dump(obj)
  File "/usr/lib/python2.5/pickle.py", line 224, in dump
    self.save(obj)
  File "/usr/lib/python2.5/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/usr/lib/python2.5/pickle.py", line 419, in save_reduce
    save(state)
  File "/usr/lib/python2.5/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.5/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.5/pickle.py", line 663, in _batch_setitems
    save(v)
  File "/usr/lib/python2.5/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/usr/lib/python2.5/pickle.py", line 401, in save_reduce
    save(args)
  File "/usr/lib/python2.5/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.5/pickle.py", line 562, in save_tuple
    save(element)
  File "/usr/lib/python2.5/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.5/pickle.py", line 600, in save_list
    self._batch_appends(iter(obj))
  File "/usr/lib/python2.5/pickle.py", line 615, in _batch_appends
    save(x)
  File "/usr/lib/python2.5/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/usr/lib/python2.5/pickle.py", line 401, in save_reduce
    save(args)
  File "/usr/lib/python2.5/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.5/pickle.py", line 562, in save_tuple
    save(element)
  File "/usr/lib/python2.5/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.5/pickle.py", line 748, in save_global
    (obj, module, name))
pickle.PicklingError: Can't pickle <class 'django.template.SimpleNode'>: it's not found as django.template.SimpleNode

Notes:
A hacky fix is attached, which preserves the semantics of SimpleNode. Since django.template.Library.simple_tag() is the only function that uses it, this may not be the optimal solution.

[Malcolm Tredinnick]

This patch can't be right. Each call to simple_tag() changes the module-level object, so they'll interfere with each other in subtle ways.

[Simon Law <simon@…>]

The patch is horribly kludgy, in order to capture the closure on func, but it should totally work properly.

I am not advocating that you actually apply this patch. :P It's just a minimally invasive change for you to use in developing a proper fix.

[Simon Law <simon@…>]

OK, so I bumped into those subtle errors that you were talking about.

Here is a revised patch where I've pulled the state out of the closures and made them explicit. This required changes to django.template.generic_tag_compiler(), but I think this is quite reasonable.

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Tim Graham]

It's unclear to me how to move forward with this ticket or if it remains an issue as the file modified by the proposed patch has changed quite a bit in 8 years.