Modular CLI Options

require 'cli/modular_options'

module DatabaseStuff
  extend CLI::WithOptions
  
  # Your mixin methods might go here
  
  cli_options do |parser|
    parser.separator 'Database Options:'
    parser.on '--db-user', 'Database username' do |v|
      cli_opts[:db_user] = v
    end
    parser.on '--db-pass', 'Database password' do |v|
      cli_opts[:db_pass] = v
    end
  end
end

module StandardOptions
  extend CLI::WithOptions
  cli_options do |parser|
    parser.on_head '-h', '--help', 'Display help' do
      cli_opts[:show_help] = true
      cli_opts[:parser] = parser
    end
  end
end

class MyApp
  include CLI::ModularOptions
  include DatabaseStuff
  include StandardOptions
  
  def cli_opts
    @cli_opts ||= Hash.new
  end
  
  def show_help
    puts cli_opts[:parser]
    Process.exit 0
  end
  
  def initialize( argv = ARGV.map(&:dup) )
    cli_opts[:positional] = new_cli_parser.parse! argv
    show_help if cli_opts[:show_help]
  end
end

# You can inherit options in a subclass
class MyDerivedApp < MyApp
  # Maybe you prefer to let the caller decide what to do about --help
  def show_help
    throw :help, cli_opts[:parser]
  end
end

# You can append more options directly to a class
class MyVerboseApp < MyApp
  extend CLI::WithOptions
  cli_options do |parser|
    parser.separator 'Options added by MyVerboseApp:'
    cli_opts[:verbose] = false
    parser.on '--verbose', 'Enable verbose output' do
      cli_opts[:verbose] = true
    end
  end
end

# The order in which callbacks are invoked is well-defined.
# Your cli_options blocks are called in a natural order that aligns
# with normal ruby inheritance semantics.
class MyQuietApp < MyVerboseApp
  cli_options do |parser|
    # This appears on the list of options after those declared in MyVerboseApp
    parser.on '--no-verbose', 'Disable verbose output' do
      cli_opts[:verbose] = false
    end
  end
end