ForeignKey to 'self' in sub-application throws error on makemigrations in Django project

Question

I'm currently working on an large Django project (version 1.10.7) and am running into an error with a model field in a sub-application. Here's what the basic structure looks like:

project/
    app_one/
        __init__.py
        apps.py
        models.py
        urls.py
        views.py
        app_two/
            __init__.py
            apps.py
            models.py
            urls.py
            views.py

The model and field in question looks like this (project/app_one/app_two/models.py):

class SampleModel(model.Model):
    parent = models.ForeignKey('self', null=True, blank=True, related_name='members')

When I run python manage.py makemigrations app_one.app_two in the root folder I get this error message:

File .../django/db/models/utils.py", line 23, in make_model_tuple "must be of the form 'app_label.ModelName'." % model ValueError: Invalid model reference 'app_one.app_two.SampleModel'. String model references must be of the form 'app_label.ModelName'.

Here is code from other files that are relevant:

project/settings.py:

INSTALLED_APPS = filter(None, (
    ...
    'app_one',
    'app_one.app_two',
    ...
)

project/app_one/app_two/apps.py:

from __future__ import unicode_literals

from django.apps import AppConfig


class AppOneAppTwoConfig(AppConfig):
    name = 'app_one.app_two'
    label = 'app_one.app_two'

project/app_one/app_two/__init__.py:

default_app_config = 'app_one.app_two.apps.AppOneAppTwoConfig'

I believe the error here is that Django is only looking for one . in the full model name (app_one.app_two.SampleModel) to separate the app label from the model name in django/db/models/utils.py, and since there are two in this case, it fails.

My question is: This seems like a weird for Django not to account for...is there anyway to retain the dot notation of the app label and still have a self-referencing ForeignKey in a sub-application?

Johan · Accepted Answer · 2018-09-25T09:42:38.653

0

As you mention, it seems to be a lookup error when the project is trying to locate your app due to the nested apps. This can be solved by specifying the app name with an app_label in the models internal meta class:

class SampleModel(models.Model):
    ...
    class Meta:
        app_label = 'app_two'

edited Sep 25 '18 at 09:42

answered Sep 24 '18 at 06:03

Johan

3,577
1
14
28

Yeah, unfortunately I tried the methods you described and that doesn't work either - same error. It seems when it parsed the related fields, it winds up referencing the app_label no matter what, and the double dots cause the same error. I was able to solve it though, and I'll create an answer to my question that highlights my solution. – Colty Harrison Sep 24 '18 at 16:33
1

Ah, have you tried adding `app_label = 'app_two'` in the Meta class of the model? – Johan Sep 24 '18 at 16:40
@ColtyHarrison Cheers, I have updated my answer in case you want to mark it as a solution for your question. – Johan Sep 25 '18 at 09:43

score 0 · Answer 2 · answered Sep 24 '18 at 16:35

0

I was able to solve this by changing the app_label to 'app_one_app_two' in apps.py. Because django references this when registering the related models, it doesn't break. All migrations are then registered under that label as well.

answered Sep 24 '18 at 16:35

Colty Harrison

43
3

ForeignKey to 'self' in sub-application throws error on makemigrations in Django project

2 Answers2