#25563: Datamigration causing incorrect behavior when custom manager is using
.defer()
----------------------------+--------------------
Reporter: coldmind | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------
Consider simple model and custom manager:
{{{
from django.db import models
class CustomManager(models.Manager):
use_in_migrations = True
def get_queryset(self, *args, **kwargs):
return super(CustomManager, self).get_queryset(
*args, **kwargs
).defer('test')
class ModelA(models.Model):
test = models.CharField(blank=True, max_length=123)
objects = CustomManager()
}}}
Also there is a simple test:
{{{
from django.test import TestCase
from .models import ModelA
class Test(TestCase):
def test_defer_bug(self):
ModelA.objects.create(test='test')
self.assertIsInstance(ModelA.objects.last(), ModelA)
}}}
With initial migration test is passing well. But, when adding a
datamigration like this (where test is evaluating a queryset, which is
using custom manager with `.defer()` inside):
{{{
# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.db import models, migrations
def test_forwards(apps, schema_editor):
ModelA = apps.get_model('blankapp', 'ModelA')
list(ModelA.objects.all())
def noop(apps, schema_editor):
return
class Migration(migrations.Migration):
dependencies = [
('blankapp', '0001_initial'),
]
operations = [
migrations.RunPython(test_forwards, noop)
]
}}}
test is failing like:
{{{
======================================================================
FAIL: test_defer_bug (blankapp.tests.Test)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/projpath/blank/blankapp/tests.py", line 8, in test_defer_bug
self.assertIsInstance(ModelA.objects.last(), ModelA)
AssertionError: <ModelA_Deferred_test: ModelA_Deferred_test object> is not
an instance of <class 'blankapp.models.ModelA'>
}}}
This is causing tests failures, when, for example, test contains FK
assignment (there is `isinstance` check).
Test if failing from
https://github.com/django/django/commit/aa5ef0d4fc67a95ac2a5103810d0c87d8c547bac
--
Ticket URL: <https://code.djangoproject.com/ticket/25563>
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