Re: custom managers and migrations

Obviously a difficult question...

On Saturday, 3 October 2015 23:54:24 UTC+1, Dan Tagg wrote:

Hi,

I'm using django 1.8.4.

1. I have added a field "deleted" to a couple of models so that when the delete button is pressed, to all intents and purposes the record will have been deleted, although it should still be accessible through the Admin site. 

2. To make this happen in a way that can't be easily accidentally ignored I have overiden "get_queryset in this manner

class AnnotationManager(models.Manager):

    def get_queryset(self):

        return super(AnnotationManager, self).get_queryset().filter(deleted=False)

and then had 

    objects = managers.AnnotationManager()

in the Model

3. I am also using AutoSlugField. To make sure that doesn't give an integrity error I have had to add another manager AllAnnotationManager and get the AutoSlugField to use it by adding the following keyword argument

manager=managers.AllAnnotationManager()

This works fine as far as integrity is concerned

4. However, if I run makemigrations, I get the following errors

  File "manage.py", line 10, in <module>

    execute_from_command_line(sys.argv)

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line

    utility.execute()

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 330, in execute

    self.fetch_command(subcommand).run_from_argv(self.argv)

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/core/management/base.py", line 393, in run_from_argv

    self.execute(*args, **cmd_options)

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/core/management/base.py", line 444, in execute

    output = self.handle(*args, **options)

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/core/management/commands/makemigrations.py", line 125, in handle

    migration_name=self.migration_name,

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/db/migrations/autodetector.py", line 43, in changes

    changes = self._detect_changes(convert_apps, graph)

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/db/migrations/autodetector.py", line 186, in _detect_changes

    self.generate_altered_fields()

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/db/migrations/autodetector.py", line 849, in generate_altered_fields

    new_field_dec = self.deep_deconstruct(new_field)

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/db/migrations/autodetector.py", line 67, in deep_deconstruct

    for key, value in kwargs.items()

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/db/migrations/autodetector.py", line 67, in <dictcomp>

    for key, value in kwargs.items()

  File "/Users/dantagg/envs/cr_3.4/lib/python3.4/site-packages/django/db/migrations/autodetector.py", line 61, in deep_deconstruct

    path, args, kwargs = deconstructed

ValueError: too many values to unpack (expected 3)

The 5 deconstructed values that are causing the problem are

False

conciliation_resources_db.managers.AllAnnotationManager

None

()

{}

The object whose deconstruct method is causing the problem is 

<class 'conciliation_resources_db.managers. AllAnnotationManager'>

Why is the manager's deconstruct method being called and how do I stop it?

Dan

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