The curious task of supporting multiple devise authenticatables by ensuring they don't have a instance method fight.

devise_sadness.rb

module Devise
  module Models
    module AggregateAuthenticatable
      extend ActiveSupport::Concern
      STRATEGIES = {:basic => Devise::Models::DatabaseAuthenticatable, :ldap => Devise::Models::LdapAuthenticatable}
      MODULES = [Devise::Models::DatabaseAuthenticatable, Devise::Models::LdapAuthenticatable]


      module ClassMethods
        def strategy_instance_methods
          MODULES.map(&:instance_methods).flatten
        end
      end

      included do
        MODULES.each { |mod| include mod }
        self.strategy_instance_methods.each do |method|
          define_method method do |*args| 
            dispatch_method method, *args
          end
        end
      end

      def respond_to?(method, include_all=false)
        if self.class.strategy_instance_methods.include? method
          strategy = STRATEGIES[current_strategy]
          return strategy.instance_methods.include?(method)
        end
        super
      end

      def dispatch_method(method, *args)
        strategy =  STRATEGIES[current_strategy]
        strategy.instance_method(method).bind(self)[*args] if respond_to?(method)
      end

      def current_strategy
        ...
      end
    end
  end
end