deprecate duplicable? and remove it from the framework

rescues are quite expensive, this is why we added the duplicable thing in the first place ;)

Not sure what the right fix is here, what values have you seen this being called on?

My only concern is that the current code does not play by the rules for arbitrary values.

Deviating from standard Ruby approaches has to be very justified in my view. If experience shows the current approach works in practice, and that avoiding rescue in those points pays off in terms of performance, then no prob (I can't personally tell).

In that case I'd perhaps document the motivation in the rdoc of duplicable?.

Looks like it's primarily used in ActiveRecord (2.3.4) in clone_attribute_value, which gets called by the dirty mechanism. So removing it in favor of rescue would impose additional execution cost on pretty much every attribute assignment that isn't duplicable (ie, integers and booleans).

Yes, and in a few more places (see the patch).

I did some isolated benchmarks and added this explanation in duplicable.rb:

http://github.com/lifo/docrails/commit/2ddbef421cb877bc219ac2737bbb...

Please feel free to close the ticket if the comment looks fine.