Can migrated apps depend on unmigrated apps?

[Carsten Fuchs]

Dear Django developers,

can apps that use migrations depend on unmigrated apps?

The documentation at
<https://docs.djangoproject.com/en/1.7/topics/migrations/#dependencies>
explains how dependencies work, and explicitly mentions that unmigrated
apps cannot depend on migrated apps.

In turn it seems to imply that migrated apps *can* depend on unmigrated
apps, but is that correct? In the docs example where `books` have a
foreign key and thus depend on `authors`, does it really work if
`authors` is unmigrated? How would it be able to run the `authors`
migration to create the table the foreign key in `books` references, if
`authors` is unmigrated?


This is an implication of my so far unfruitful attempts to add
migrations to an older, existing app as described in thread
<https://groups.google.com/forum/#!topic/django-users/lVS24BGFouo>,
where I have exactly this situation:

The older app is still unmigrated (as I could not yet find a way to
overcome the problems with making it migrated), and would like to create
a new one in the meanwhile. The new app has a foreign key on a model in
the old one, and now I'm wondering if it is wise to proceed...?

Any hints and help would very much be appreciated! :-)

Best regards,
Carsten

[Carsten Fuchs]

Hi all,

Am 04.02.2015 um 18:26 schrieb Carsten Fuchs:
> can apps that use migrations depend on unmigrated apps?

Anyone please?

It seems like this works in practice, but this still looks like a
contradiction to me, and I would still be interested in some feedback
for a firmer foundation for ongoing work…

Best regards,
Carsten

[Michael Pöhn]

This is all covered in Djangos documentation...
https://docs.djangoproject.com/en/1.7/topics/migrations/#dependencies

Let me paste the relevant parts for you:

»Be aware, however, that unmigrated apps cannot depend on migrated apps,
by the very nature of not having migrations. This means that it is not
generally possible to have an unmigrated app have a ForeignKey or
ManyToManyField to a migrated app; some cases may work, but it will
eventually fail.

Warning: Even if things appear to work with unmigrated apps depending on
migrated apps, Django may not generate all the necessary foreign key
constraints.«

br.
Michael

[Carsten Fuchs]

Hi Michael,

Am 17.02.2015 um 22:44 schrieb Michael Pöhn:
> This is all covered in Djangos documentation...
> https://docs.djangoproject.com/en/1.7/topics/migrations/#dependencies

Well, no... please see below.

> Let me paste the relevant parts for you:
>

> »Be aware, however, that unmigrated apps cannot depend on migrated apps, [...]«

This explains that unmigrated apps cannot depend on migrated apps.

My question is about the opposite case: Can migrated apps depend on
unmigrated apps? I've explained the apparent problem in greater detail
in my original post.

Best regards,
Carsten

[Collin Anderson]

Hi Carsten,

I in my experience, it _sometimes_ works to have migrated apps depend on unmigrated apps.

If you haven't yet, you could try generating migrations for the unmigrated app, and reference them using MIGRATION_MODULES.

Collin

[Carsten Fuchs]

Hi Collin,

thank you very much for your reply!

Am 19.02.2015 um 19:35 schrieb Collin Anderson:
> If you haven't yet, you could try generating migrations for the
> unmigrated app, and reference them using MIGRATION_MODULES.

I've tried this, and my real problem is that I have problems with this
step, i.e. applying the initial migrations to the unmigrated app: Please
see <https://groups.google.com/forum/#!topic/django-users/lVS24BGFouo>
for details. Any help about this would very much be appreciated!

Many thanks and best regards,
Carsten