ugettext_lazy with arguments causes RuntimeError

[Karmo Rosental]

If I use arguments with translations I get RuntimeError.

help_text=_('e.g. %(foo)s or %(bar)s') % {
            'foo': 'footxt', 'bar': 'bartxt'})

This code causes following error:

Traceback (most recent call last):
  File "./manage", line 13, in <module>
    django.setup()
  File "/usr/local/lib/python2.7/dist-packages/django/__init__.py", line 21, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/usr/local/lib/python2.7/dist-packages/django/apps/registry.py", line 106, in populate
    app_config.import_models(all_models)
  File "/usr/local/lib/python2.7/dist-packages/django/apps/config.py", line 190, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/home/karmo/Dev/project/api/models.py", line 205, in <module>
    class Test(Model):
  File "/home/karmo/Dev/project/api/models.py", line 222, in Test
    'foo': 'footxt', 'bar': 'bartxt'})
  File "/usr/local/lib/python2.7/dist-packages/django/utils/functional.py", line 179, in __mod__
    return six.text_type(self) % rhs
  File "/usr/local/lib/python2.7/dist-packages/django/utils/functional.py", line 144, in __text_cast
    return func(*self.__args, **self.__kw)
  File "/usr/local/lib/python2.7/dist-packages/django/utils/translation/__init__.py", line 83, in ugettext
    return _trans.ugettext(message)
  File "/usr/local/lib/python2.7/dist-packages/django/utils/translation/trans_real.py", line 317, in ugettext
    return do_translate(message, 'ugettext')
  File "/usr/local/lib/python2.7/dist-packages/django/utils/translation/trans_real.py", line 298, in do_translate
    _default = translation(settings.LANGUAGE_CODE)
  File "/usr/local/lib/python2.7/dist-packages/django/utils/translation/trans_real.py", line 201, in translation
    default_translation = _fetch(settings.LANGUAGE_CODE)
  File "/usr/local/lib/python2.7/dist-packages/django/utils/translation/trans_real.py", line 184, in _fetch
    for app_config in reversed(list(apps.get_app_configs())):
  File "/usr/local/lib/python2.7/dist-packages/django/apps/registry.py", line 125, in get_app_configs
    self.check_ready()
  File "/usr/local/lib/python2.7/dist-packages/django/apps/registry.py", line 119, in check_ready
    raise RuntimeError("App registry isn't ready yet.")
RuntimeError: App registry isn't ready yet.

Seems it uses non-lazy ugettext in django/utils/translation/init.py.

If I remove dictionary from the end of _() then this error disappears.

I'm using Django 1.7b4.

[Tim Graham]

Note this will raise a different message on master due to 9618d68b345fe69c787f8426b07e920e647e05f3.

[Claude Paroz]

This is expected behavior with the current implementation, the % (mod) operator on lazy strings does produce the final string.
We might experiment with delaying the translation in this case and find out (a) if it's possible and (b) if the behavior change is not too much backwards incompatible.
At the very least, we could improve the documentation.

[Aymeric Augustin]

This code was silently doing the wrong thing in Django < 1.7. Now it's failing loudly. That's an intended and documented consequence of the app-loading refactor.

[Tim Graham]

Claude, do you think we need a documentation enhancement now that we have the "The translation infrastructure cannot be initialized before the apps registry is ready. Check that you don't make non-lazy gettext calls at import time." error message? If so, maybe you could suggest a location for that documentation and retitle the ticket to make it more suitable for beginners to contribute?

[Claude Paroz]

I think the section in ​https://docs.djangoproject.com/en/1.10/topics/i18n/translation/#working-with-lazy-translation-objects will need to be updated, particularly after format_lazy will be added (#26866 / #27067).

[Claude Paroz]

I guess that the format_lazy addition in docs should now be sufficient.