generate_role.rb

require 'yaml'

module Puppet::Parser::Functions
  newfunction(:generate_role, :type => :rvalue) do |args|
    fact      = args[0]
    path      = args[1]
    default   = args[2]   


    begin
      db = YAML.load_file(path)

      found = db.detect { |key,value| value.include?(fact) }

      if found 
        found.first    
      else
        if default
          default 
        else
          raise Puppet::ParseError, "Function[generate_role] given host(#{fact}) isn't found in #{path}"     
        end
      end

    rescue Psych::SyntaxError => e
      raise Puppet::ParseError, "Invalid format in #{path}: #{e.message} - #{e.backtrace}}"
    rescue StandardError => e
      raise Puppet::ParseError, "UnknownError: #{e.message} - #{e.backtrace}"
    end
  end
end