form_builder_helpers.rb

module FormBuilderHelpers
  class Html5
    def self.options_from(object, attribute)
      return {} unless object.class.respond_to?(:validators_on)
      
      {}.tap do |options|
        options[:required] = true if object.class.validators_on(attribute).any? { |validator| validator.is_a?(ActiveModel::Validations::PresenceValidator) }
        
        if validator = object.class.validators_on(attribute).select { |validator| validator.is_a?(ActiveModel::Validations::InclusionValidator) && validator.options[:in].is_a?(Range) }.last
          options[:min] = validator.options[:in].min
          options[:max] = validator.options[:in].max
        end
      end
    end
  end
end