[skateinmars]

I'm late to the party but we have a list of some outdated gems that are still not compatible with Rails 4 (we use a long-lived branch for rails 4 compatibility that should be merged once rails 4 is released and all our dependencies are compatible).

* client_side_validations : There is an outdated rails 4 branch

* client_side_validations-simple_form : this is trickier because it also needs compatibility with the next simple_form major version. AFAIK no work is done at the moment

* active_enum : looks like simply updating the gemspec may be enough

* ransack : there is an outdated rails-4 branch, I'm not sure what the current compatibility status is

Other than that a few gems have still not released stable versions with rails 4 compatibility and only have support in a RC or even just their master branch (for instance: simple_form, database_cleaner, sass-rails)