Template `date` filter fails with TypeError

[Nicola Peduzzi]

This code:

from django.template import Context, Template
import datetime
t = Template('{{ d|date:"Y" }}')
c = Context({'d':datetime.datetime.now()})
t.render(c)

Fails with:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/template/base.py", line 209, in render
    return self._render(context)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
    return self.nodelist.render(context)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/template/base.py", line 903, in render
    bit = self.render_node(node, context)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/template/base.py", line 917, in render_node
    return node.render(context)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/template/base.py", line 957, in render
    output = self.filter_expression.resolve(context)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/template/base.py", line 674, in resolve
    new_obj = func(obj, *arg_vals)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/template/defaultfilters.py", line 771, in date
    return formats.date_format(value, arg)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/utils/formats.py", line 136, in date_format
    return dateformat.format(value, get_format(format or 'DATE_FORMAT', use_l10n=use_l10n))
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/utils/formats.py", line 110, in get_format
    for module in get_format_modules(lang):
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/utils/formats.py", line 82, in get_format_modules
    modules = _format_modules_cache.setdefault(lang, list(iter_format_modules(lang, settings.FORMAT_MODULE_PATH)))
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/utils/formats.py", line 51, in iter_format_modules
    if not check_for_language(lang):
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/utils/translation/__init__.py", line 181, in check_for_language
    return _trans.check_for_language(lang_code)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/utils/lru_cache.py", line 125, in wrapper
    result = user_function(*args, **kwds)
  File "/Users/Nikso/Work/Antlos/AntlosServer/virtual/lib/python2.7/site-packages/django/utils/translation/trans_real.py", line 409, in check_for_language
    if not language_code_re.search(lang_code):
TypeError: expected string or buffer

[Baptiste Mispelon]

Hi,

That code works for me. Can you show the content of your settings (in particular, anything related to i18n)?

Thanks.

[Marten Kenbeek]

To reproduce, start a new project using Django's project template. I believe that USE_L10N = True is the issue, though it might be a combination of settings that causes it.

[Baptiste Mispelon]

OK, I can now reproduce this (the trick is to execute the code in a ./manage.py shell).

I've tracked down the regression (this code used to work in 1.7) to commit 543df07720181fe23737ba14f1a261ff6f37f49c.

As knbk pointed out on IRC, the problem seems to be that translation.get_language() returns None because the BaseManagementCommand calls deactivate_all [1]

Even though it's a regression, I'm not sure it should be treated as a release blocker because I fail to see a valid use-case where this change would cause a problem.

[1] ​https://github.com/django/django/blob/master/django/core/management/base.py#L391

[Claude Paroz]

Surely, the fact that get_language might return None is new in 1.8, and it appears that some functions (like check_for_language in this issue) are not prepared to receive a None language. Still, I think that returning None when no language is activated is the right thing. I only hope we'll not have to patch too much Django internals for that...

To fix this one, the following patch might be sufficient:

django/utils/translation/trans_real.py

@@ -406 +406 @@
     <https://www.djangoproject.com/weblog/2007/oct/26/security-fix/>.
     """
     # First, a quick check to make sure lang_code is well-formed (#21458)
-    if not language_code_re.search(lang_code):
+    if lang_code is None or not language_code_re.search(lang_code):
         return False
     for path in all_locale_paths():
         if gettext_module.find('django', path, [to_locale(lang_code)]) is not None:

Test needed, of course.

[Claude Paroz <claude@…>]

In 7a0d9b5:

Fixed #24569 -- Made some translation functions accept None value

get_language() can return None when translations are deactivated.
Thanks Nicola Peduzzi for the reporti and Tim Graham for the review.

[Claude Paroz <claude@…>]

In 3a76276:

[1.8.x] Fixed #24569 -- Made some translation functions accept None value

get_language() can return None when translations are deactivated.
Thanks Nicola Peduzzi for the reporti and Tim Graham for the review.
Backport of 7a0d9b5cda from master.