Unable to use Custom Base class

Hello!

I’m trying to create a new base event My base class looks like this:

  class AbstractEvent(models.Model):
      jira_issue = models.CharField(max_length=20, default='NOTSYNCED')

My config looks like this:

...

SCHEDULER_BASE_CLASSES = {
    'Event': ['downtime_calendar.models.AbstractEvent']
}

SCHEDULER_ADMIN_FIELDS = {
    'Event': [('jira_issue',)]
}

...

But whenever I try to run the./manage.py makemigrations && ./manage.py migrate I got a nasty error

   Applying schedule.0006_auto_20171018_1520...Traceback (most recent call last):
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/django/db/backends/mysql/base.py", line 101, in execute
    return self.cursor.execute(query, args)
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/MySQLdb/cursors.py", line 250, in execute
    self.errorhandler(self, exc, value)
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/MySQLdb/connections.py", line 50, in defaulterrorhandler
    raise errorvalue
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/MySQLdb/cursors.py", line 247, in execute
    res = self._query(query)
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/MySQLdb/cursors.py", line 411, in _query
    rowcount = self._do_query(q)
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/MySQLdb/cursors.py", line 374, in _do_query
    db.query(q)
  File "/home/gonzalo/VirtualEnvs/apcela_web_project/lib/python3.5/site-packages/MySQLdb/connections.py", line 277, in query
    _mysql.connection.query(self, query)
_mysql_exceptions.OperationalError: (1829, "Cannot drop column 'id': needed in a foreign key constraint 'schedule_eventrelation_event_id_8c57a7b4_fk_schedule_event_id' of table 'apcela_web_app.schedule_eventrelation'")

I’m thinking that either something is missing in the documentation that I’m supposed to do, since I’m not sure why is that django migration is trying to remove the ID from the schedule_event table

[jdufresne]

IMO, the _BASE_CLASSES feature is a difficult to maintain feature with lots of unusual edge cases and unexpected consequences. I think the project should consider dropping it to ease maintainability, predictability, and consistency with other reusable Django apps. My project uses quite a few reusable Django apps and I’m not aware of any other using a similar _BASE_CLASSES like feature, which might help explain why this is a common source of bugs (and one currently holding back Django 2.0 support). Are you aware of any other reusable Django apps with a similar feature? Do they hit the same issue?

@llazzaro What are you thoughts on deprecating and removing this feature? If you agree, I’m happy to open a pull request to do so. It would certainly simplify maintenance.

@ggarcia24 The Event model already supports relationships to arbitrary other objects through the EventRelation model. Have you considered using that to solve your use case?

[jdufresne]

I’ve created a proof of concept of my proposal above at #377. All feedback on it is welcome.