'ManyToOneRel' object has no attribute 'get_limit_choices_to'

[Seb G]

Summary

The newly introduced feature in Django 3.2

ModelAdmin.autocomplete_fields now respects ForeignKey.to_field and ForeignKey.limit_choices_to when searching a related model)

Triggers a bug when used on ManyToOneRel:

Traceback (most recent call last):
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/contrib/admin/sites.py", line 250, in wrapper
    return self.admin_view(view, cacheable)(*args, **kwargs)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/views/decorators/cache.py", line 44, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/contrib/admin/sites.py", line 232, in inner
    return view(request, *args, **kwargs)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/contrib/admin/sites.py", line 417, in autocomplete_view
    return AutocompleteJsonView.as_view(admin_site=self)(request)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/views/generic/base.py", line 98, in dispatch
    return handler(request, *args, **kwargs)
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/contrib/admin/views/autocomplete.py", line 25, in get
    self.object_list = self.get_queryset()
  File "/home/me/.virtualenvs/myproject/lib/python3.7/site-packages/django/contrib/admin/views/autocomplete.py", line 42, in get_queryset
    qs = qs.complex_filter(self.source_field.get_limit_choices_to())
AttributeError: 'ManyToOneRel' object has no attribute 'get_limit_choices_to'

Steps to reproduce

Use the following model:

class Ticket(models.Model)
    user = models.ForeignKey("users.User", on_delete=models.PROTECT, verbose_name=_("user"))

And the following admin:

@admin.register(Ticket)
class TicketAdmin(admin.ModelAdmin):
    autocomplete_fields = ("user",)

[Seb G]

Cannot reproduce with my own base example since a ForeignKey instance is passe to get_queryset, as opposed to the ManyToOneRel that is passed in my real-life unexposed example. Investigating.

[Seb G]

For some reason, in my base example, the data- attributes on the HTML select are as follow:

• data-app-label="myapp"
• data-model-name="ticket"
• data-field-name="user"

While in my real-life project they seem to be reversed as follow:

• data-app-label="users"
• data-model-name="user"
• data-field-name="ticket"

This causes a ManyToOneRel to be passed to AutocompleteJsonView.get_queryset instead of the expected ForeignKey.

[Mariusz Felisiak]

autocomplete_fields doesn't support reverse M2O relations. Please reopen the ticket if you can debug your issue and provide a sample project.

[Seb G]

The fact is that i do have an autocomplete field that was working perfectly in 3.1 and fails to work in 3.2, due to this new feature. I will keep trying to replicate and provide a sample project.

[Seb G]

Problem solved. Cause was traced down to an evolution of the BaseModelAdmin.formfield_for_foreignkey method:

if db_field.name in self.get_autocomplete_fields(request):
    kwargs['widget'] = AutocompleteSelect(db_field.remote_field, self.admin_site, using=db)

became

if db_field.name in self.get_autocomplete_fields(request):
    kwargs['widget'] = AutocompleteSelect(db_field, self.admin_site, using=db)

and this broke an override from a package we use.

[Mariusz Felisiak]

Thanks for the follow up.

[Timothy Allen]

For anyone who finds this ticket with the same error: this error will be triggered if you are using the third party Django admin packages django-admin-autocomplete-filter or django-admin-rangefilter. Upgrade to the latest versions (as of this writing, django-admin-rangefilter==0.6.3 and django-admin-autocomplete-filter==0.8.3) and it should resolve the error.

[Cash Costello]

For those confused by the previous comment, there is no django-admin-autocomplete-filter version 0.8.3 and the newest version is 0.7.1 which is not compatible with Django 3.2 or greater. Link to the github repo for that package: ​https://github.com/farhan0581/django-admin-autocomplete-filter