id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
33323	On custom migrations, import of model classes with app.get_model('appname', 'ModelName') ignores overwritten models.Model methods	Andreas Scheucher	nobody	"Given migration:

{{{
from django.db import migrations
from designs.models import Design


def fix_wrong_design_sheet_data(apps, schema_editor):
    # do not import Model classes like in the line below. Overwritten methods are not executed.
    # Design = apps.get_model('designs', 'Design')

    for design in Design.objects.all().iterator():
        if design. uuid in ['79f53b09-7069-480e-a8d9-d88ec0aad8d0', 'e26230cb-a9c7-4ee1-9523-0f2f70cf5c98']:
            design.language = 'nt'
        design.save(
            force_insert=False,
            force_update=True,
            using='default',
            update_fields=['id_slug', 'language'])


class Migration(migrations.Migration):

    dependencies = [
        ('designs', '0027_related_design_cols_to_many_many_remove_old_col'),
    ]

    operations = [
        migrations.RunPython(fix_wrong_design_sheet_data),
    ]
}}}

Model class:

{{{
class Design(models_mixins.PkUUID, models_mixins.TrackingMixin):
    niche = models.CharField(blank=False, null=True, max_length=50)
    id = models.CharField(blank=False, null=True, max_length=4)
    variant = models.CharField(blank=False, null=True, max_length=1)
    language = models.CharField(max_length=2, default=None)

    # this field is filled by the .save() method
    id_slug = models.CharField(max_length=61, blank=False, null=True)
    ...

    def save(self, force_insert: bool, force_update: bool, using: Optional[str], update_fields: Optional[Iterable[str]]) -> None:
        print('new save')
        int_id = int(self.id)
        nslid = f'{self.niche}-{int_id:04}-{self.variant}--{self.language}'
        self.id_slug = nslid
        return super().save(force_insert=force_insert, force_update=force_update, using=using, update_fields=update_fields)
}}}

When imported with `from designs.models import Design`, then the Design.save method is called.

BUG:
Importing the Design model class with `Design = apps.get_model('designs', 'Design')` the Design.save method is not called.
"	Bug	closed	Migrations	3.2	Normal	invalid			Unreviewed	0	0	0	0	0	0