id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
21173	Django DateTimeInput determines language/locale at startup time but this may change later, resulting in validation errors	django-locale-issue@…	Claude Paroz	"My application works in two locales, 'nl' and 'en'. In some situations, when editing content, Django formats datetimes in the wrong format which won't validate later.

The problem, I suspect is in the fact that DateTimeInput determines/stores the locale format in its __init__, which means at startup/import time in most cases. It cannot handle a changing locale later.

This is with Django 1.4.x but the relevant code doesn't appear to be any different on 1.5.x

I've tested/verified the issue in an interactive django shell session:


{{{
# In my settings I have LANGUAGE_CODE = 'nl' 
# but the user can switch to english later.
# Forms, fields and widgets are usually initialized at startup/import time
# DateTimeField users DateTimeInput which uses the current language to determine the preferred format

In [1]: from django.contrib.auth.forms import UserChangeForm

In [2]: print UserChangeForm().fields['last_login'].widget.format
%d-%m-%Y %H:%M:%S

# this is a rather dutch format
# imagine the user switches to english
In [3]: from django.utils import translation

In [4]: translation.activate('en')

In [5]: print UserChangeForm().fields['last_login'].widget.format
%d-%m-%Y %H:%M:%S

# the format remains unchanged, which isn't good but not fatal. Let's format a string using this
In [6]: from datetime import datetime

In [7]: now = datetime.now()

In [8]: print UserChangeForm().fields['last_login'].widget._format_value(now)
26-09-2013 15:33:13

# now feed this string back to the field, as if the form was filled in and then submitted without change
In [11]: print UserChangeForm().fields['last_login'].to_python(""26-09-2013 15:33:13"")
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
/home/ivo/.buildout/eggs/Django-1.4.5-py2.7.egg/django/core/management/commands/shell.pyc in <module>()
----> 1 print UserChangeForm().fields['last_login'].to_python(""26-09-2013 15:33:13"")

/home/ivo/.buildout/eggs/Django-1.4.5-py2.7.egg/django/forms/fields.pyc in to_python(self, value)
    435                 return None
    436             value = '%s %s' % tuple(value)
--> 437         result = super(DateTimeField, self).to_python(value)
    438         return from_current_timezone(result)
    439 

/home/ivo/.buildout/eggs/Django-1.4.5-py2.7.egg/django/forms/fields.pyc in to_python(self, value)
    354                         except ValueError:
    355                             continue
--> 356         raise ValidationError(self.error_messages['invalid'])
    357 
    358     def strptime(self, value, format):

ValidationError: [u'Enter a valid date/time.']

# oops!

}}}

"	Bug	closed	Forms	dev	Normal	fixed	forms,widgets,locale		Accepted	1	0	0	0	0	0