pythonconfig_parser_example.rb

require 'rubygems'
require 'pp'
require 'treetop'

Treetop.load_from_string(DATA.read)

parser = PyConfigParser.new
conf = <<-STUFF
[section name]
  key:value
  other_key:value2

[other section]
  foo = bar, baz
  narf: bla

[some other stuff]
  white: space
STUFF

if config = parser.parse(conf)
  config = config.build
else
  puts parser.failure_reason
end

pp config
# => 
# { 
#   "some other stuff" => { "white" =>"space" },
#   "section name"     => { "other_key" => "value2", "key"=> "value" },
#   "other section"    => { "foo" => ["bar", "baz"], "narf"=> "bla" }
# }


__END__
grammar PyConfig
  rule main
    section*
    {
      def build
        @config = {}
        elements.each do |section| 
          @config[section.name] = section.build
        end
        @config
      end
    }
  end

  rule section
    '[' sectionname ']' eol
    pairs:(sectionvalue eol)+ 
    white*
    {
      def name
        sectionname.text_value
      end
  
      def build
        return pairs.elements.inject({}) do |pairs, elt|
          pairs.merge!(elt.sectionvalue.build)
          pairs
        end
      end
    }
  end

  rule sectionname
  (string / white)+
  end

  rule sectionvalue
  white* key separator value
  {
    def build
      separator.build(key, value)
    end
  }
  end

  rule separator
  white* ':' white*
  {
    def build(key, value)
      {key.text_value => value.text_value.strip}
    end
  }
  /
  white* '=' white*
  {
    def build(key, value)
      {key.text_value => value.text_value.split(',').map {|val| val.strip }}
    end
  }
  end

  rule key
    string
  end

  rule value
    (string / ',' / space)*
  end

  rule string
    [a-zA-Z_0-9]+
  end

  rule white
    (space / eol)
  end

  rule space
    [ \t]
  end

  rule eol
    "\n" / ("\r" "\n"?)
  end
end