Re: [1.8] Odd error on makemigrations when moving model to another application

On 3/11/2015 9:55 AM, Alex Heyden wrote:
> I tried putting the model back in its original module with some much
> smaller changes, but I'm getting the same error. The error is nonsense
> in the current context.
>
> Is there some intermediate state saved somewhere when you try to run
> makemigrations?

Not as far as I can tell. I too have had difficulty moving models
between apps. It is in my too-hard basket for the moment. However ...

When I try again I'll create the model-to-be-moved in its new app and
get that working properly. I would definitely do a makemigration but
edit the migration file prior to migrating to use a forwards_func()
method to get the data across and entrenched in its proper relations
with other models on creation. Finally, when all is working I'd bravely
drop the old model in a separate migration.

hth

Mike

>
> On Mon, Nov 2, 2015 at 4:34 PM, Alex Heyden <mindsbreath@gmail.com
> <mailto:mindsbreath@gmail.com>> wrote:
>
> Traceback first:
>
> ./manage.py makemigrations
> Traceback (most recent call last):
> Â File "./manage.py", line 10, in <module>
> Â Â execute_from_command_line(sys.argv)
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/core/management/__init__.py",
> line 351, in execute_from_command_line
> Â Â utility.execute()
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/core/management/__init__.py",
> line 343, in execute
> Â Â self.fetch_command(subcommand).run_from_argv(self.argv)
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/core/management/base.py",
> line 394, in run_from_argv
> Â Â self.execute(*args, **cmd_options)
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/core/management/base.py",
> line 445, in execute
> Â Â output = self.handle(*args, **options)
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/core/management/commands/makemigrations.py",
> line 125, in handle
> Â Â migration_name=self.migration_name,
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/db/migrations/autodetector.py",
> line 43, in changes
> Â Â changes = self._detect_changes(convert_apps, graph)
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/db/migrations/autodetector.py",
> line 110, in _detect_changes
> Â Â self.old_apps = self.from_state.concrete_apps
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/db/migrations/state.py",
> line 170, in concrete_apps
> Â Â self.apps = StateApps(self.real_apps, self.models,
> ignore_swappable=True)
> Â File
> "/home/me/.virtualenvs/fluent/local/lib/python2.7/site-packages/django/db/migrations/state.py",
> line 248, in __init__
> Â Â raise ValueError(msg.format(field=operations[0][1],
> model=lookup_model))
> ValueError: Lookup failed for model referenced by field
> sdd.Documentation.opportunity: sdd.......governance.models.Opportunity
>
> Needless to say, sdd.......governance.models.Opportunity is not a
> valid path to anything.
>
> The Opportunity model was moved from the sdd application to the
> governance application. Documentation has a foreign key to
> Opportunity. The Python itself is correct. It used to be a direct
> reference to the class in the module, now it's an imported
> reference. All of the foreign keys are handled in the same way.
> Nothing is done by string.
>
> I'm ok with a one-off solution for the migration, but I'm more
> interested in /why/Â the model path is so far off and what I might
> have done to cause it.
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