Django-polymorphic models having issues making migrations on 1.7

Question

I am using Django 1.7 and django-polymorphic for my models

class ReferenceItem(PolymorphicModel):
    created_at = models.DateTimeField(_('date created'), auto_now_add=True, db_index=True)
    updated_at = models.DateTimeField(_('date modified'), auto_now=True, db_index=True)
    uuid = UUIDField(auto=True, unique=True)
    description = models.CharField(max_length=255)

class OrderItem(ReferenceItem):
    order = models.ForeignKey('Order', related_name='items')
    sku = models.CharField(max_length=255)
    quantity = models.IntegerField()
    unit_price = models.DecimalField(max_digits=10, decimal_places=2)
    amount = models.DecimalField(max_digits=10, decimal_places=2)
    tax_rate = models.DecimalField(max_digits=3, decimal_places=2)
    commission_rate = models.DecimalField(max_digits=3, decimal_places=2)

When I ran makemigrations I got this error:

raise InvalidBasesError("Cannot resolve bases for %r\nThis can happen if you are inheriting models from an app with migrations (e.g. contrib.auth)\n in an app with no migrations; see https://docs.djangoproject.com/en/1.7/topics/migrations/#dependencies for more" % new_unrendered_models)
django.db.migrations.state.InvalidBasesError: Cannot resolve bases for [<ModelState: 'orders.OrderItem'>]
This can happen if you are inheriting models from an app with migrations (e.g. contrib.auth)

I have been through the django ticket but still unaware what the problem is.

score 6 · Accepted Answer · answered Sep 15 '14 at 23:53

6

This has got nothing to do with polymorphic package I guess.

What I have done to fix it is to comment out my apps, leaving the builtin django apps, run ./manage.py migrate to migrate the system apps, then uncomment my apps, and run ./manage.py makemigrations

answered Sep 15 '14 at 23:53

James Lin

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Thank you for this simple solution! – lub0v Oct 11 '14 at 08:41

jhrr · Answer 2 · 2019-04-14T11:13:05.033

You can also try this:

1) Add a migrations directory to the problematic app (orders in this case).

mkdir /path/to/your/app/migrations

2) Add an __init__.py to that same migrations directory.

touch /path/to/your/app/migrations/__init__.py

3) Run python manage.py makemigrations <yourapp>

4) Migrate any other apps, individually or as a whole, if you are fortunate.

And that should solve it. It's less error prone and hacky than depending on commenting out any installed apps, which isn't really consistent or reproducible.

Django-polymorphic models having issues making migrations on 1.7

2 Answers2

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