Can not marshal an ActiveRecord object with anything in association_cache

[danielfarrell]

We are in process of upgrading to 3.2.x from 3.0.x and are running into a "singleton can't be dumped" when saving a AR object(user) into the session.

I've narrowed it down to an AR object not being able to be marshaled if there is anything in the association_cache. It works if I clear the cache, or if I don't use a relation and instead just memoize with a find_by_user_id on the other model.

It looks to have started sometime in the 3.2 series. Anyone have thoughts? Is this something I should work around?

[steveklabnik]

/cc @tenderlove @jonleighton

[tenderlove]

Can you give us reproduction steps? Even a full demo rails app would be fine.

[danielfarrell]

Looks like this does not happen in a new clean app. Must be something screwed up in our app that is causing this. Sorry for wasting your time, should have checked that first.

[danielfarrell]

For anyone else who happens to come by this. The issue is from the composite_primary_keys gem.