# File lib/hiera/backend.rb, line 79
      def datasources(scope, override=nil, hierarchy=nil)
        if hierarchy
          hierarchy = [hierarchy]
        elsif Config.include?(:hierarchy)
          hierarchy = [Config[:hierarchy]].flatten
        else
          hierarchy = ["common"]
        end

        hierarchy.insert(0, override) if override

        hierarchy.flatten.map do |source|
          source = interpolate_config(source, scope, override)
          if source == "" or source =~ /(^\/|\/\/|\/$)/
            Hiera.debug("Ignoring bad definition in :hierarchy: \'#{source}\'")
          else
            yield(source)
          end
        end
      end