[Sqlalchemy-tickets] Issue #4321: Inheriting from classical mapped class via intermediate class fails (zzzeek/sqlalchemy)

[Torsten L. <iss...@bi...>]

New issue 4321: Inheriting from classical mapped class via intermediate class fails
https://bitbucket.org/zzzeek/sqlalchemy/issues/4321/inheriting-from-classical-mapped-class-via

Torsten Landschoff:

We are currently trying to migrate a medium sized project from using classical SQLAlchemy mappings to declarative mappings. Not sure if this is supported but it seemed to work (I did not find anything in the documentation).

For some classes I ran into problems though because SQLAlchemy does not identify the mapped class due to an unmapped intermediate class.

I attached a patch with a full testcase to reproduce the issue. While the documentation does not seem to discuss this usage, I consider it highly unintuitive that just introducing a class into the inheritance hierarchy causes breakage.

My current workaround is to add the last mapped class explicitly as a base class.

Greetings, Torsten