Model.refresh_from_db() does not refresh related objects

[Aleksander Zamojski]

After testing my application with Django 2.0.13 I noticed few of my test started failing (they were working on Django 2.1). After further investigation, I figured out the problem was coming from refresh_from_db method.

Here is a test that show the problem:

def test_error_on_refresh_from_db(self):
    def add_one(id):
        task_model = FakeTask.objects.get(id=id)
        task_model.task_group.finished_tasks_number = F('finished_tasks_number') + 1
        task_model.task_group.save()
        task_model.task_group.refresh_from_db()
        task_model.save()
        self.assertEqual(task_model.task_group.finished_tasks_number, 1)

    task_group_model = FakeTaskGroup.objects.create()
    task_model = FakeTask.objects.create(task_group=task_group_model)
    add_one(task_model.id)
    task_model.refresh_from_db()
    self.assertEqual(task_model.task_group.finished_tasks_number, 1)

Here you can find the definition (light version) of the this models:

class FakeTaskGroup(models.Model):
   finished_tasks_number = models.PositiveIntegerField(default=0)

class FakeTask(models.Model):
    task_group = models.ForeignKey(FakeTaskGroup, on_delete=models.CASCADE)

[Tim Graham]

Django 2.0 is end-of-life April 2019 and only receives security and data loss fixes until then (but most likely there won't be another release).