How to solve filer and sites dependencies problem in my project

Question

Currently I have started working on Django project given by me for learning purpose.

I have done all kind of necessary setup in my virtualenv and when running migrate command on my project I am getting below kind of dependencies problems as below.

I have tried to find solution online and django doc but clueless.

Traceback

Traceback (most recent call last):
  File "manage.py", line 40, in <module>
    execute_from_command_line(sys.argv)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
    utility.execute()
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/core/management/__init__.py", line 345, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/core/management/base.py", line 348, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/core/management/base.py", line 399, in execute
    output = self.handle(*args, **options)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 89, in handle
    executor = MigrationExecutor(connection, self.migration_progress_callback)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/db/migrations/executor.py", line 20, in __init__
    self.loader = MigrationLoader(self.connection)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/db/migrations/loader.py", line 49, in __init__
    self.build_graph()
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/db/migrations/loader.py", line 306, in build_graph
    _reraise_missing_dependency(migration, parent, e)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/db/migrations/loader.py", line 276, in _reraise_missing_dependency
    raise exc
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/db/migrations/loader.py", line 302, in build_graph
    self.graph.add_dependency(migration, key, parent)
  File "/home/moon/production/remax/remax_env/lib/python3.6/site-packages/django/db/migrations/graph.py", line 126, in add_dependency
    parent
django.db.migrations.exceptions.NodeNotFoundError: Migration core.0002_auto_20200408_0215 dependencies reference nonexistent parent node ('filer', '0008_auto_20200408_0215')

Snippet from migration file as below. 0002_auto_20200408_0215.py

class Migration(migrations.Migration):

    dependencies = [
        ('filer', '0008_auto_20200408_0215'),
        ('sites', '0003_auto_20200408_0215'),
        ('core', '0001_initial'),
    ]

I have thought to comment dependencies lines from 0002_auto_20200408_0215.py files but my friend told me it should work without removing any lines.

Can someone pls guide me what I am doing wrong & how to solve this issue.

Thanks.

Answer 1

There doesn't appear to be a django-filer migration with the name mentioned 0008_auto_20200408_0215 .

https://github.com/divio/django-filer/tree/master/filer/migrations

Given that the suffix _20200408_0215 is identical to your own application's migration file -- was your migration file perhaps edited?

When you depend on migrations of external packages your application will use those shipped with the package. In a normal work flow you should not be generating migration files for other applications.

TLDR; Solution

Find the latest migration available in your installed 'django-filer' application and edit your migration file to use that.

Example

ls /usr/local/lib/python3.7/site-packages/filer/migrations/
0001_initial.py             0004_auto_20160328_1434.py  0007_auto_20161016_1055.py  0010_auto_20180414_2058.py  __pycache__
0002_auto_20150606_2003.py  0005_auto_20160623_1425.py  0008_auto_20171117_1313.py  0011_auto_20190418_0137.py
0003_thumbnailoption.py     0006_auto_20160623_1627.py  0009_auto_20171220_1635.py  __init__.py

You will have to check for python3.6 instead of python3.7 and you may want to check dist-packages as well as site-packages depending on your distribution and how you installed django-filer.

My test application has a models.py like this:

from django.db import models
from filer.fields.file import FilerFileField

# Create your models here.
class Myobject(models.Model):
    name = models.CharField(max_length=100)
    other_name = models.CharField(max_length=100)
    file_field = FilerFileField(blank=True, null=True, on_delete=models.SET_NULL)

Which generates dependencies in a migration file like so:

# Generated by Django 3.0.5 on 2020-04-15 10:21

from django.db import migrations
import django.db.models.deletion
import filer.fields.file


class Migration(migrations.Migration):

    dependencies = [
        ('filer', '0011_auto_20190418_0137'),
        ('testthis', '0001_initial'),
    ]
<snip>

If I change that dependency ('filer', '0011_auto_20190418_0137'), at all I get your same error.

raise NodeNotFoundError(self.error_message, self.key, origin=self.origin)
django.db.migrations.exceptions.NodeNotFoundError: Migration testthis.0002_myobject_file_field dependencies reference nonexistent parent node ('filer', '0011_auto')

Align your migration file with the latest django-filer migration available on your system.

Answer 2

Before migrating, type python manage.py showmigrations and you will see all apps with their migrations (applied or not). Check if there indeed is a 'filer' app with a migration named '0008_auto_20200408_0215'. If there is not, the app might not be in your INSTALLED_APPS (project/settings.py) and you should add it, or remove the dependency from the dependencies list (although I don't recommend this)