Handling of ManyToMany fields is... missing? about django-parler HOT 6 CLOSED

Hi! thanks for getting in touch.

I'm curious what kind of code you're working with, because I can't quite understand the situation from the error message alone. It almost looks like you're connecting to the translated model directly instead of the shared model. Can you post something here, or as a Gist? That way I can also share some caveats. :)

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Here's what I'm doing. It's pretty basic; trying to work solely with the shared model, too. Let me know if you need more info.

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The main problem here is that a ManyToManyField - despite its name - is not a real field. Every M2M field creates a table which links the models together.

Given the following models:

class A(TranslatedModel):
    translations = TranslatedFields(
        b_set = models.ManyToManyField('B', related_name='a_set')
    )

class B(models.Model):
    pass

You get an implicit translation model for A:

class ATranslation(models.Model):
    b_set = models.ManyToManyField('B', related_name='a_set')

And an implicit M2M model:

class ATranslation_b(models.Model):
    atranslation = models.ForeignKey('A')
    b = models.ForeignKey('B')

This M2M table can be used to navigate from a translated A to B just fine, but the related_name in B is kinda useless as you end up reaching the translation model which is counter intuitive.

A modified TranslatedManyToManyField could be smart and run A.objects.filter(translations__language=get_current_language(), translations__b_set=b) in the related manager and only give you B objects of the current language.

This is a tough nut to crack as it will probably require a lot of tinkering with Django internals. It would be a great addition to django-parler though.

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@egasimus Without traceback almost always is harder to tell why some error is raised.

I saw your error when preparing a patch for #131. I'm not sure if this error is raised for you at the same place where it was raised for me (In the TranslatedFieldsModel._get_field_values() when running under Django 1.8). You can test my changes in #132 to see if it will work for you.

In order to fully support M2M fields in django-parler I think that more work need to be done, but probably my changes are the beginning.

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Thread necromancy. I added M2M support in #300.

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PR is merged!

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