Thor task to check config/config.yml against config/config.template.yml for missing keys.

config.thor

class Config < Thor
  PATH = 'config/config.yml'

  desc 'get KEY', "get value of key in #{PATH}"
  def get(key)
    %w(development production).each do |env|
      puts "#{env}:"
      begin
        value = get_config(key, env)
        puts "  #{key} => '#{get_config(key, env)}'"
      rescue
        puts "  #{key} => UNDEFINED"
      end
    end
  end

  desc 'set KEY VALUE', "set key to value in #{PATH} then restart app"
  method_option :debug, :type => :boolean, :default => false, :aliases => "-d", :desc => "Debug"
  method_option :verbose, :type => :boolean, :default => true, :aliases => "-v", :desc => "Verbose"
  def set(key, value)
    set_config(key, value)
  end

  desc 'check', "check #{PATH} keys against template"
  method_option :env, :type => :string, :default => 'development', :aliases => "-e", :desc => "Environment must be either 'development' or 'production'"
  def check
    env = options[:env].to_s.downcase
    abort "Environment value not acceptable" unless %w(development production).include?(env)
    check_config_keys(env)
  end

  private

    def get_config(key, env)
      config = load_yml(PATH, env)
      raise "Key '#{key}' not defined" unless config.has_key?(key)
      config[key]
    end

    def set_config(key, value)
      temp = Tempfile.new('temp_config.txt')
      error = true
      File.read(PATH).each_line do |line|
        if match = /#{key}: (.*)/.match(line)
          error = false
          puts "Key Found. Current value '#{match[1]}'." if options[:verbose]
          temp.puts line.sub(/#{key}: .*/, "#{key}: #{value}")
        else
          temp.puts line
        end
      end
      if error
        puts "! Error: Key '#{key}' not found"
      else
        puts "Moving new file into place..." if options[:verbose]
        FileUtils.mv(temp.path, PATH, :noop => options[:debug], :verbose => options[:verbose])
        puts "Restarting application..." if options[:verbose]
        FileUtils.touch('tmp/restart.txt', :noop => options[:debug], :verbose => options[:verbose])
      end
      return error
    end

    def check_config_keys(env = nil)
      ext = File.extname(PATH)
      config_name = File.basename(PATH)
      template_name = "#{File.basename(PATH, ext)}.template#{ext}"
      config = load_yml(PATH, env)
      template = load_yml("config/#{template_name}", env)
      missing = template.reject { |k, v| config.has_key?(k) }
      error = false
      puts "Checking '#{config_name}' keys..."
      if missing.any?
        puts "Config file '#{config_name}' missing keys:"
        missing.each {|k, v| puts "    #{k}"}
        error = true
      end
      missing = config.reject {|k, v| template.has_key?(k)}
      if missing.any?
        puts "Template file '#{template_name}' missing keys:"
        missing.each {|k, v| puts "    #{k}"}
        error = true
      end
      puts "=> #{error ? 'FAIL' : 'PASS'}"
    end

    def load_yml(file, env = nil)
      yml = YAML.load(File.read(file))
      if env.nil?
        yml
      else
        abort "! Error: Environment '#{env}' not defined" unless yml.has_key?(env)
        yml[env]
      end
    end

end