Multiple Conditions with scopes

[the8472]

The Defining Abilities wiki page states the following about using scopes:

You cannot use this with multiple can definitions that match the same action and model since it is not possible to combine them.

I would like to question this supposed impossibility.

Here is a quick proof of concept (read: hack) that can merge Hash and ActiveRecord::Relation conditions using arel 2.0.10 and cancan 1.6.7. It currently does not support negative abilities - which could be remedied by making the reduce phase a bit smarter - and always kicks in, even when no scopes are present.

All joins used in the scopes and hashes are also converted to outer joins since different joins may be necessary for different where conditions. This might have unintended side-effects and require an additional distinct/group by clause.

https://gist.github.com/1952018

[the8472]

Updated the patch with some improved, cleaner logic that should handle negated scopes properly.

[derekprior]

Hmmm, I don't see reference to this on the defining abilities wiki. A google search found it here, however:
https://github.com/ryanb/cancan/wiki/defining-abilities-with-blocks

I'm going to tag this as a feature request and for discussion. I have not tried your gist, but I did peruse it. To me it seems to be too down-in-the-weeds for inclusion in a gem like cancan, but that's not ultimately up to me.

[the8472]

To me it seems to be too down-in-the-weeds

I assume you're talking about accessing the arel underlying the scopes. It's not too different from what rails is doing internally, apart from the converting inner to outer joins, which is an issue with rails not supporting outer joins properly.

Outer joins are necessary for complex queries and in fact cause issues for cancan in other places too, see #374 (and a few others) for example.

[xhoy]

Dear submitter, Since cancan/raynB hasn't been active for more than 6 months and no body else then ryam himself has commit permissions the cancan project is on a stand still.
Since cancan has several issues including missing support for rails 4 cancan is moving forward to cancancan. More details on: #994

If your feel that your pull request or bug is still applicable (and hasn't been merged in to cancan) it would be really appreciated if you would resubmit it to cancancan (https://github.com/cancancommunity/cancancan)

We hope to see you on the other side!