Choosy: Picking your arguments carefully

This is a small DSL library for creating command line clients in Ruby. It is largely inspired by the choice, commander, and optcomplete.py libraries, though it makes some different design decisions than they do. It is opinionated software.

This library should:

• Make creating command line clients relatively easy.
• Make creating supercommands like git, subversion, and gem easier.
• Allow you to add validation logic for your arguments within the parsing phase.
• Allowing for dependencies between options, so that you can more easily validate related options (i.e. if the--bold flag requires the --font Arial flag, then you should be able to ask for the --font option to be validated first, and then the --bold option.
• Allow you to customize its output using your own formatting system.
• Allow you to customize the output to your specifications.

This library should never:

• Interact with your execution logic. You can attach executors to commands for convenience, but the execution phase should be delegated to you, not the parsing library. Separation of concerns, people.
• Rely on display or user interface libraries like Highline, since this is only for parsing command lines.
• Pollute your namespaces with my DSL function names. (I really, really hate it when libraries do this.)

Examples

#!/usr/bin/env ruby -w
# foo.rb

$LOAD_PATH.unshift File.join(File.dirname(File.dirname(__FILE__)), 'lib')
require 'choosy'

FOO_VERSION = '1.0.1'

class FooExecutor
  def execute!(args, options)
    puts "BOLDED!!" if options[:bold]
    options[:count].times do
      puts "#{options[:prefix]}#{options[:words].push('foo').join(',')}#{options[:suffix]}"
    end
    puts "and #{args.join ' '}"
  end
end

foo_cmd = Choosy::Command.new :foo do |foo|
  # Add a class to do the execution when you call foo_cmd.execute!
  # You can also use a proc that takes the options and the args, like:
  #    executor { |args, options| puts 'Hi!' }
  executor FooExecutor.new

  # When used as a subcommand, you need a summary for the help screen
  summary "This is a nice command named 'foo'"

  # You can add your custom printer by giving the
  # full path to an ERB template file here.  
  # The default printer is :standard, but you can 
  # also use the builtin printer :erb, with the :tempates
  # parameter to set the erb template you wish to use. The 
  # output can be colored or uncolored, though the
  # default is colored.
  printer :standard, :color => true, :header_styles => [:bold, :green]

  para 'Prints out "foo" to the console'
  para 'This is a long description of what foo is an how it works. This line will assuredly wrap the console at least once, since it it such a long line, but it will be wrapped automatically by the printer, above. If you want to, you can add write "printer :standard, :max_width => 80" to set the maximum column width that the printer will allow (not respected by ERB templates).'

  header 'Required Options:' # Formatted according to the header_styles for the printer

  # A shorthand for a common option type.
  # It adds the '-p/--prefix PREFIX' infomation for you.
  single :prefix, "A prefix for 'foo'" do
    default '<'
    required
  end

  # The long way to do the same thing as above, except with
  # explicitly named dependencies
  option :suffix => [:prefix] do
    short '-s'
    long  '--suffix', 'SUFFIX'
    desc  'A suffix for "foo"'
    required

    validate do |suffix, options|
      if suffix == options[:prefix]      
        die "You can't matching prefixes and suffixes, you heathen!"
      end
    end
  end

  # Just like the 'single' method above, except now it automatically
  # requires/casts the argument to this flag into an integer.  These commands
  # also take an optional hash as the last argument, which can be used instead
  # of a block.
  integer :count, 'The number of times to repeat "foo"', :required => true

  header 'Options:', :bold, :blue # Format this header differently, overrides 'header_styles'

  option :words do
    short '-w'
    long  '--words', 'WORDS+' # By default, the '+' at the end
                                # means that this takes multiple
                                # arguments.  You put a '-' at
                                # the end of the argument list
                                # to stop parsing this option
                                # and allow for regular args.
    desc  "Other fun words to put in quotes"

    # Sets the exact count of the number of arguments it accepts.
    # also allowable are the single selectors :zero and :one.
    # By default, the option 'WORDS+' sets the range to be
    # {:at_least => 1, :at_most => 1000 }
    count :at_least => 2, :at_most => 10

    validate do |words, options|
      words.each do |word|
        if word !~ /\w+/
          die "I can't print that: #{word}"
        end
      end
    end
  end

  # Alternatively, we could have done the following:
  strings :words, "Other fun words to put in quotes" do
    count 2..10
    default []
    validate do |words, options|
      words.each do |word|
        if word !~ /\w+/
          die "I can't print that: #{word}"
        end
      end
    end
  end

  # Yet another shorthand notation for options, since they
  # are boolean by default. Here, we add a negation to the
  # long flag of the option, creating [-b|--bold|--un-bold] flags.
  # By default, calling 'negate' in a block without an argument
  # uses the '--no-' prefix instead.
  boolean :bold, "Bold this option", :default => false, :negate => 'un'

  # Tail options

  # When any of the simpler notations are suffixed with a '_' 
  # character, the short option is always suppressed.
  boolean_ :debug, "Prints out extra debugging output."

  # The '_' characters are replaced with '-' in flags, so the 
  # following creates a '--[no-]color' flag.
  boolean_ :color, "Turns on/off coloring in the output. Defalt is on." do
    negate
    default true
    validate do
      foo.command.alter do
        printer :standard, :colored => false
      end
    end
  end

  # Adds the standard -h/--help option.
  # Should skip the '-h' flag if already set.
  help  # Automatically adds the description if not passed an argument. You can supply your own

  # Adds the --version option.
  version "Foo: #{FOO_VERSION}"

  # Now, add some validation for any addtional arguments
  # that are left over after the parsing the options.
  arguments do
    metaname 'ARGS'
    count 1..10
    validate do |args, options|
      if args.empty?
        die "You have to pass in empty arguments that do nothing!"
      end
      if args.count == 10
        die "Whoa there!  You're going argument crazy!"
      end
    end
  end
end

if __FILE__ == $0
  # Parses and validates the options.
  args =  ['--prefix', '{', 
           '--suffix', '}',
           '--words', 'high', 'there', 'you', '-', 
           # The '-' stops parsing this option, so that:
           'handsom', 'devil',
           'http://not.posting.here', # will be regular arguments
           '-c', '3', # Count
           '--', # Stops parsing all arguments
           '-h', '--help', '-v', '--version' # Ignored
          ]
  result = foo_cmd.parse!(args)

  require 'pp'
  pp result[:prefix]        # => '{'
  pp result[:suffix]        # => '}'
  pp result[:count]         # => 3
  pp result[:bold]          # => false
  pp result[:words]         # => ['high', 'there', 'you']
  pp result.args            # => ['handsom', 'devil',
                            #     'http://not.posting.here',
                            #     '-h', '--help', '-v', '--version']
  pp result.options         # => {:prefix => '{', :suffix => '}'
                            #     :count => 3, :bold => false,
                            #     :words => ['high', 'there', 'you'],
                            #     :debug => false, :color => true}

  # Now, call the command that does the actual work.
  # This passes the foo_cmd.options and the foo_cmd.args
  # as arguments to the executors 'execute!' method.
  #
  # This allows you to easily associate command classes with
  # commands, without resorting to a hash or combining
  # execution logic with command parsing logic.
  foo_cmd.execute!(args)    # {high,there,you,foo}
                            # {high,there,you,foo}
                            # {high,there,you,foo}
                            # and handsom devil http://not.posting.here -h --help -v --verbose

end

Super Commands

You can also combine multiple choices into an uber-choice, creating commands that look a lot like git or subversion.

First, we create another command.

#!/usr/bin/env ruby -w
# bar.rb

$LOAD_PATH.unshift File.join(File.dirname(File.dirname(__FILE__)), 'lib')
require 'choosy'

# Create a new command
bar_cmd = Choosy::Command.new :bar do
  executor do |args, options|
    if options[:bold]
      puts "BOLD!!!"
    else
      puts "plain"
    end
  end

  summary "Displays when this is a subcommand"
  para "Just prints 'bar'"
  para "A truly unremarkable command"

  header 'Option:'
  boolean :bold, "Bolds something" do
    negate 'un'
  end

  # Because there is no bar.arguments call,
  # it is now an error if there are extra
  # command line arguments to this command.
end

if __FILE__ == $0
  args = ['--un-bold']

  result = bar_cmd.parse!(args)

  require 'pp'
  pp result.options[:bold]           # => false
  pp result.args                     # => []

  bar_cmd.execute!(args)             # => 'plain'

  args << 'should-throw-error'
  bar_cmd.execute!(args)
end

We can now create our super command.

#!/usr/bin/env ruby -w
# superfoo.rb

$LOAD_PATH.unshift File.join(File.dirname(File.dirname(__FILE__)), 'lib')
$LOAD_PATH.unshift File.join(File.dirname(File.dirname(__FILE__)), 'examples')
require 'choosy'
require "foo"
require "bar"

SUPERFOO_VERSION = "1.0.1"

superfoo = Choosy::SuperCommand.new :superfoo do
  summary "This is a superfoo command"
  para "Say something, dammit!"

  # You can also add commands after instantiation.
  # Note that, when added, these commands have their
  # -h/--help/--version flags suppressed, so you'll
  # need to add those flags here.
  command bar_cmd
  command foo_cmd

  # Creates a 'help' command, message optional
  help "Prints this help message"

  # Create some global options that are parsed
  # defore result options

  # Here, check that a YAML file exists, and attempt
  # to load it's parsed contents into this option.
  # There is also a 'file' type that checks to see
  # if the file exists. With both 'file' and 'yaml',
  # if the file is missing, the option fails with an
  # error.
  yaml :Config, "Configure your superfoo with a YAML configuration file." do
    default File.join(ENV['HOME'], '.superfoo.yml')
  end

  # Adds a global --version flag.
  version "#{SUPERFOO_VERSION}"
end

if __FILE__ == $0
  args = ['foo',
          '-c', '5',
          '--config', '~/.superfoo',
          '--prefix', '{',
          '--suffix', '}',
          'cruft',
          'bar',
          '--bold']

  result = superfoo.parse!(args)

  require 'pp'
  pp result[:config]        # => '~/.superfoo'
  pp result.name            # => :foo
  pp result[:prefix]        # => '{'
  pp result[:suffix]        # => '}'
  pp result[:count]         # => 2
  pp result[:bold]          # => true
  pp result.options         # => {:prefix => '{', :suffix => '}'
                            #     :count => 2,
                            #     :bold => true, 
                            #     :words => [],
                            #     :config => '~/.superfoo' }
  pp result.args            # => ['cruft', 'bar']

  # Now, we can call the result
  superfoo.execute!(args)   ## Calls superfoo.result.execute!
                            ## Prints:
                            # BOLDED!!
                            # {foo}
                            # {foo}
                            # and cruft bar

  # Instead of parsing the 'bar' parameter as an argument to
  # the foo command, so that when the first argument that matches
  # another command name is encountered, it stops parsing the
  # current command and passes the rest of the arguments to the
  # next command.
  #
  # In this case, we call the 'alter' method to use the DSL
  # syntax again to alter this command.
  #
  # You can also set this inside a SuperChoosy.new {...}
  # block.
  superfoo.alter do
    parsimonious
  end

  result = superfoo.parse!(args)

  pp result.name                    # => :superfoo
  pp result[:config]                # => '~/.superfoo'
  pp result.subresults[0].name      # => :foo
  pp result.subresults[0][:prefix]  # => '{'
  pp result.subresults[0][:suffix]  # => '}'
  pp result.subresults[0][:count]   # => 2
  pp result.subresults[0][:bold]    # => true
  pp result.subresults[0].options   # => {:prefix => '{', :suffix => '}'
                                    #     :count => 2,
                                    #     :bold => false, 
                                    #     :words => [],
                                    #     :config => '~/.superfoo' }
  pp result.subresults[0].args      # => ['cruft']

  pp result.subresults[1].name      # => :bar
  pp result.subresults[1][:bold]    # => true
  pp result.subresults[1].options   # => {:bold => true,
                                    #     :config => '~/.superfoo'}
  pp result.subresults[1].args      # => []

  # Now, execute the results in order
  superfoo.execute!(args)       ## Same as:
                                #  results.each do |subcommand|
                                #    command.execute!
                                #  end
                                ## Prints:
                                # {foo}
                                # {foo}
                                # and cruft
                                # BOLDED BAR
end

TODO: Output Printing