Order descending on translated fields

[slahmar]

Hello,

I bumped into a problem when trying to use Django-filters with Django-hvad to descending order (ascending order works perfectly).

Here is my problem :

I have a non-translatable model with a foreign key to a TranslatableModel :

class MyModel(models.Model):
    other_model = models.ForeignKey('models.OtherModel')   

class OtherModel(TranslatableModel):
    translations = TranslatedFields(
        name=models.CharField()
    ) 

I want to order by name DESC. I use a TranslationAwareManager to filter and order my objects, but when I do the request ?ordering=-other_model__name I get the following error :

WrongManager at /api/products/

Accessing translated fields like product.name from an regular model requires a translation-aware queryset, obtained with the .language() method. For regular, non-translatable models, you can get one using hvad.utils.get_translation_aware_manager

From my investigations, I understood that -other_model__name was not translated as -other_model__translations__name as it's done for other_model__name.
For now I wrote a workaround to detect the - and split it, then use some TranslationAwareQueryset underlying functions : _translate_fieldnames and _filter_extra.
So I can get the translated name anyway and then put a - in front of it, and then order by that.

These few lines are really simple and could be easily added to the _translate_fieldnames function, which would allow the descending order to properly work (and allow me to keep my code focused on my business needs 😄 ). I can do a PR if you are interested !

Regards,
Salomé