Awful Ruby hack for forcing the last argument (generally an options hash) to all of a class's methods to be a HashWithIndifferentAccess.

options_with_indifferent_access.rb

module OptionsWithIndifferentAccess
  module ClassMethods
    def method_added(method_name)
      unless caller[1].match(/`method_added'/)
        define_method("_orig_#{method_name}".intern, instance_method(method_name))
        define_method(method_name) do |*args, &block|
          if args[-1].is_a? Hash
            args[-1] = HashWithIndifferentAccess.new(args[-1])
          end
          self.send "_orig_#{method_name}", *args, &block
        end
      end
    end
  end
  def self.included(base)
    base.extend(ClassMethods)
  end
end

test_class_12.rb

class TestClass12
  include OptionsWithIndifferentAccess

  def foo(opts={})
    puts "opts is a #{opts.class}"
  end
end

# tc12 = TestClass12.new
# tc12.foo(test: true)
# => opts is a ActiveSupport::HashWithIndifferentAccess