# File lib/hiera/backend.rb, line 31
      def datadir(backend, scope)
        backend = backend.to_sym

        if Config[backend] && Config[backend][:datadir]
          dir = Config[backend][:datadir]
        else
          dir = Hiera::Util.var_dir
        end

        if !dir.is_a?(String)
          raise(Hiera::InvalidConfigurationError,
                "datadir for #{backend} cannot be an array")
        end

        interpolate_config(dir, scope, nil)
      end