Rails 2.3.5 Bug With accepts_nested_attributes_for

The Setup

At work, our application has a series of questions it asks users, and an administrator can set a target of what he thinks (or wants) the answer to be.

class Question < ActiveRecord::Base
  has_many :targets
  accepts_nested_attributes_for :targets, :allow_destroy => true
end

class Target < ActiveRecord::Base
  belongs_to :question
end

The administrator fills the form out, choosing a target or not, and Rails will save, update, or destroy it as normal. Well, almost. Apparently there is a bug in Rails 2.3.5 that will save the child model twice, and we're experiencing that now.

What I Want To Do

Upgrade to Rails 3.1, get all the new hotness and bug fixes, and not worry about this problem.

What I'm Going To Do

Since we don't have the resources to upgrade Rails (yet...), we need a workaround. Here's what we came up with.

after_save :ensure_one_target_while_in_draft

def ensure_one_target_while_in_draft
  if draft? && targets.count > 1
    targets[1..-1].each { |t| t.destroy }
  end
end

This problem only comes up when a question has not been activated and is still in draft mode. Once it's activated, the administrator cannot change the target but only add additional ones. So while in that state, and if there are multiple targets, destroy all but the first. This needs to be in an after_save callback because the double-save does not happen until after the question is saved. It's not elegant, but it works. I don't want to try to patch Rails and remember to deal with that later when we finally do upgrade, and the situation is isolated enough that there isn't a performance hit and it's easy to remove once it's no longer necessary. Elegant? No. But it's a bug fix for the framework, it's well documented in the code, and it works.