[Sqlalchemy-tickets] Issue #4150: .contains fails with "chained" association proxies in 1.2 (zzzeek/sqlalchemy)

[dairiki N. <iss...@bi...>]

New issue 4150: .contains fails with "chained" association proxies in 1.2
https://bitbucket.org/zzzeek/sqlalchemy/issues/4150/contains-fails-with-chained-association

dairiki NA:

The attached script fails with `sqlalchemy.exc.InvalidRequestError`: `contains() doesn't apply to a scalar endpoint; use ==` in SQLAlchemy==1.2.  It works with SQLAlchemy==1.1.15 (and before).

The crux here is:

```
#!python


Team.events = association_proxy('eventteams', 'event')
```


where the proxied attribute is itself an association proxy:

```
#!python


EventTeam.event = association_proxy('division', 'event')
```

In this case the expression `Team.events.contains(some_event)` is what elicits the exception.