Helper for migrations in django-cms for plugins which get a model and previously had none.

djangocms_migration_helper.py

# anywhere_you_want.py
def create_plugins_from_cmsplugin(new_model_app, new_plugin_model_name,
                                  new_plugin_name, apps=None):
    """
    Create plugins for `new_plugin_name` from CMSPlugin-Plugins. This is
    necessary if you add a model to a plugin which previously had none.
    """
    if apps is None:
        from django.apps.registry import apps as dj_apps
        apps = dj_apps
    try:
        cms_plugin = apps.get_model('cms', 'CMSPlugin')
        new_model = apps.get_model(new_model_app, new_plugin_model_name)
        _new_model = True
    except LookupError:
        _new_model = False
    if _new_model:
        old_objects = cms_plugin.objects.filter(plugin_type=new_plugin_name)
        for old_obj in old_objects:
            new_obj = new_model(
                # fields for the cms_cmsplugin table
                id=old_obj.id,
                position=old_obj.position,
                language=old_obj.language,
                plugin_type=new_plugin_name,
                creation_date=old_obj.creation_date,
                changed_date=old_obj.changed_date,
                parent=old_obj.parent,
                placeholder=old_obj.placeholder,
                depth=old_obj.depth,
                numchild=old_obj.numchild,
                path=old_obj.path,
            )
            # get all childs
            childs = cms_plugin.objects.filter(parent_id=old_obj.id)
            # save childs before parent deletion by setting parent_id to NULL
            for c in childs:
                c.parent_id = None
                c.save()
            old_obj.delete()
            new_obj.save()
            # set parent_id again and save childs
            for c in childs:
                c.parent_id = new_obj.id
                c.save()
    return _new_model
  
  
# my_migration.py
from django.db import migrations

from my_app.where_the_function_lives import create_plugins_from_cmsplugin


def forwards(apps, schema_editor):
    _my_model = create_plugins_from_cmsplugin(
        'my_app', 'MyCustomPluginModel', 'MyCustomPluginPublisher',
        apps)
    if not _my_model:
        return


class Migration(migrations.Migration):
    operations = [
        migrations.RunPython(forwards, migrations.RunPython.noop),
    ]
    dependencies = [
        ('my_app', '00XY_previous_migration_name'),
    ]