# File lib/chef/mixin/template.rb, line 72
        def source_listing
          @source_listing ||= begin
            line_index = line_number - 1
            beginning_line = line_index <= SOURCE_CONTEXT_WINDOW ? 0 : line_index - SOURCE_CONTEXT_WINDOW
            source_size = SOURCE_CONTEXT_WINDOW * 2 + 1
            lines = @template.split(/\n/)
            contextual_lines = lines[beginning_line, source_size]
            output = []
            contextual_lines.each_with_index do |line, index|
              line_number = (index+beginning_line+1).to_s.rjust(3)
              output << "#{line_number}: #{line}"
            end
            output.join("\n")
          end
        end