# File lib/rabl/engine.rb, line 54
    def cache_key
      return unless defined?(@_cache_key)

      @_full_cache_key ||= begin
        cache_key = Array(@_cache_key) + [@_options[:root_name], @_options[:format]]

        if digestor_available? && respond_to?(:lookup_context) && lookup_context
          template = @_options[:template] || @virtual_path

          digest = \
            if Gem::Version.new(Rails.version) >= Gem::Version.new('4.1')
              Digestor.digest(:name => template, :finder => lookup_context)
            else
              Digestor.digest(template, :rabl, lookup_context)
            end

          cache_key << digest
        end

        cache_key
      end
    end