rule for detecting format error in gettext translations

[spaceone]

import gettext
_ = gettext.NullTranslations().gettext # ugettext, ngettext
var = 'baz'
# incorrect:
_('foo %s bar' % var)
_('foo {} bar'.format(var))
_(f'foo {var} bar')
# correct:
_('foo %s bar') % var
_('foo {} bar').format(var)

those 3 cases should be detected in a new rule:
→ calls to _ (the conventional name of gettext) should only be done with a contant string as argument.

[charliermarsh]

Is the error that you're supposed to leave the parameters unfilled?

[charliermarsh]

(Seems like a reasonable rule, I'm just not familiar with the API.)

[Jackenmen]

The error is that you're supposed to use constant strings, not dynamic ones as that passed string is used as a key during the lookup in message catalog.

I think that ideally this should support not just the most basic gettext call accepting a single argument but also calls to gettext, ngettext, and so on:
https://docs.python.org/3/library/gettext.html

[spaceone]

thanks for the feedback, I clarified the initial description.

[charliermarsh]

Thank you!