Cl

OptionParser based CLI support for rapid CLI development in an object-oriented context.

This library wraps Ruby's OptionParser for parsing your options under the hood, so you get all the goodness that the Ruby standard library provides.

On top of that it adds a rich and powerful DSL for defining, validating, and normalizing options, as well as automatic and gorgeous help output (modeled after gem --help).

Further documentation is available on rubydoc.info

Examples in this README are included from examples/readme. More examples can be found in examples. All examples are guaranteed to be up to date by the way of being verified on CI.

Basic Usage
Command Registry
Runners
Command DSL
- Commands
- Description, Summary, Examples
- Abstract
- Arguments
- Types
- Splat
- Options
- Aliases
- Defaults
- Deprecations
- Downcase
- Enum
- Example
- Format
- Internal
- Min and Max
- Negations
- Note
- Secret
- See Also
- Types
- Required Options
Config Files
Environment Variables

Basic Usage

module Owners
  class Add < Cl::Cmd
    register :add

    summary 'Add one or more owners to an existing owner group'

    description <<~str
      Use this command to add one or more owners to an existing
      owner group.

      [...]
    str

    args :owner

    opt '-t', '--to TO', 'An existing owner group'

    def run
      # implement adding the owner as given in `owner` (as well as `args`)
      # to the group given in `to` (as well as `opts[:to]`).
      p owner: owner, to: to, to?: to?, args: args, opts: opts
    end
  end
end

# Running this, e.g. using `bin/owners add one,two --to group` will instantiate the
# class `Owners::Add`, and call the method `run` on it.

# e.g. bin/owners
#
# args normally would be ARGV
args = %w(add one --to group)

Cl.new('owners').run(args)

# Output:
#
#   {:owner=>"one", :to=>"group", :to?=>true, :args=>["one"], :opts=>{:to=>"group"}}

Cl.new('owners').run(%w(add --help))

# Output:
#
#   Usage: owners add [owner] [options]
#
#   Summary:
#
#     Add one or more owners to an existing owner group
#
#   Description:
#
#     Use this command to add one or more owners to an existing
#     owner group.
#
#     [...]
#
#   Arguments:
#
#     owner           type: string
#
#   Options:
#
#     -t --to TO      An existing owner group (type: string)
#        --help       Get help on this command

Command Registry

Commands are Ruby classes that extend the class Cl::Cmd.

They register to a Ruby class registry in order to decouple looking up command classes from their Ruby namespace.

For example:

module Cmd
  class One < Cl::Cmd
    register :one
  end

  class Two < Cl::Cmd
    register :two
  end
end

p Cl::Cmd[:one] # => Cmd::One
p Cl::Cmd[:two] # => Cmd::Two

Commands can be registered like so:

module One
  class Cmd < Cl::Cmd
    register :'cmd:one'
  end
end

By default commands auto register themselves with the underscored name of the last part of their class name (as seen in the example above). It is possible to turn this off using:

Cl::Cmd.auto_register = false

Command auto-registration can cause name clashes when namespaced commands have the same demodulized class name. For example:

class Git < Cl::Cmd
  # auto-registers as :git
end

module Heroku
  class Git < Cl::Cmd
    # also auto-registers as :git
  end
end

It is recommended to turn auto-registration off when using such module structures.

Runners

Runners lookup the command to execute from the registry, by checking the arguments given by the user for registered command keys.

With the two command classes One and Two from the example above (and assuming that the executable that calls Cl is bin/run) the default runner would recognize and run the following commands:

$ bin/run one something else
# instantiates One, passing the args array `["something", "else"]`, and calls the instance method `run`

$ bin/run two
# instantiates Two, passing an empty args arry `[]`, and calls the instance method `run`

The default runner also supports nested namespaces, and checks for command classes with keys separated by colons. For instance:

module Git
  class Pull < Cl::Cmd
    register :'git:pull'

    arg :branch

    def run
      p cmd: registry_key, args: args
    end
  end
end

# With this class registered (and assuming the executable that calls `Cl` is
# `bin/run`) the default runner would recognize and run it:
#
# $ bin/run git:pull master # instantiates Git::Pull, and passes ["master"] as args
# $ bin/run git pull master # does the same

Cl.new('run').run(%w(git:pull master))
# Output:
#
#   {:cmd=>:"git:pull", :args=>["master"]}

Cl.new('run').run(%w(git pull master))
# Output:
#
#   {:cmd=>:"git:pull", :args=>["master"]}

Runners are registered on the module Cl::Runner. It is possible to register custom runners, and use them by passing the option runner to Cl.new:

module Git
  class Pull < Cl::Cmd
    register :'git:pull'

    arg :branch

    def run
      p cmd: registry_key, args: args
    end
  end
end

# With this class registered (and assuming the executable that calls `Cl` is
# `bin/run`) the default runner would recognize and run it:
#
# $ bin/run git:pull master # instantiates Git::Pull, and passes ["master"] as args
# $ bin/run git pull master # does the same

Cl.new('run').run(%w(git:pull master))
# Output:
#
#   {:cmd=>:"git:pull", :args=>["master"]}

Cl.new('run').run(%w(git pull master))
# Output:
#
#   {:cmd=>:"git:pull", :args=>["master"]}

See Cl::Runner::Default for more details.

There also is an experimental runner :multi, which supports rake-style execution of multiple commands at once, like so:

bin/rake db:drop production -f db:create db:migrate production -v 1

See the example rakeish for more details.

Command DSL

The DSL is defined on the class body.

Commands

Commands are classes that are derived from the base class Cl::Cmd.

Description, Summary, Examples

The description, summary, and examples are used in the help output.

module Owners
  class Add < Cl::Cmd
    register :add

    summary 'Add one or more owners to an existing owner group'

    description <<~str
      Use this command to add one or more owners to an existing
      owner group.
    str

    examples <<~str
      Adding a single user to the group admins:

        owners add user --to admins

      Adding a several users at once:

        owners add one two three --to admins
    str
  end
end

Cl.new('owners').run(%w(add --help))

# Output:
#
#   Usage: owners add [options]
#
#   Summary:
#
#     Add one or more owners to an existing owner group
#
#   Description:
#
#     Use this command to add one or more owners to an existing
#     owner group.
#
#   Options:
#
#     --help      Get help on this command
#
#   Examples:
#
#     Adding a single user to the group admins:
#
#       owners add user --to admins
#
#     Adding a several users at once:
#
#       owners add one two three --to admins

Abstract

Command base classes can be declared abstract in order to prevent them from being identified as a runnable command and to omit them from help output.

This is only relevant if a command base class is registered. See Command Registry for details.

class Base < Cl::Cmd
  abstract
end

class Add < Base
  register :add

  def run
    puts 'Success'
  end
end

Cl.new('owners').run(%w(add))

# Output:
#
#   Success

Cl.new('owners').run(%w(base))

# Output:
#
#   Unknown command: base

Arguments

Arguments can be declared like so:

arg :arg_name, description: 'arg description', type: :[array|string|integer|float|boolean]

This will define an attr_accessor on the Cmd class. I.e. in the following example the method ownsers will be available on the Cmd instance:

class Add < Cl::Cmd
  register :add

  arg :owner

  def run
    p owner: owner
  end
end

Cl.new('owners').run(%w(add one))

# Output:
#
#   {:owner=>"one"}

Types

Arguments can have a type. Known types are: :array, :string, :integer, :float, :boolean.

The type :array makes sure the argument accessible on the Cmd instance is a Ruby Array. (This currently only supports arrays of strings).

If the option sep is given on the argument, then the argument value is split using this separator.

class Add < Cl::Cmd
  register :add

  arg :owners, type: :array, sep: ','

  def run
    p owners: owners
  end
end

Cl.new('owners').run(%w(add one,two))

# Output:
#
#   {:owners=>["one", "two"]}

Other types cast the given argument to the expected Ruby type.

class Cmd < Cl::Cmd
  register :cmd

  arg :one, type: :integer
  arg :two, type: :float
  arg :three, type: :boolean

  def run
    p [one.class, two.class, three.class]
  end
end

Cl.new('owners').run(%w(cmd 1 2.1 yes))

# Output:
#
#   [Integer, Float, TrueClass]

Splat

Array arguments support splats, modeled after Ruby argument splats.

For example:

class Lft < Cl::Cmd
  register :lft

  arg :a, type: :array, splat: true
  arg :b
  arg :c

  def run
    p [a, b, c]
  end
end

class Mid < Cl::Cmd
  register :mid

  arg :a
  arg :b, type: :array, splat: true
  arg :c

  def run
    p [a, b, c]
  end
end

class Rgt < Cl::Cmd
  register :rgt

  arg :a
  arg :b
  arg :c, type: :array, splat: true

  def run
    p [a, b, c]
  end
end

Cl.new('splat').run(%w(lft 1 2 3 4 5))

# Output:
#
#   [["1", "2", "3"], "4", "5"]

Cl.new('splat').run(%w(mid 1 2 3 4 5))

# Output:
#
#   ["1", ["2", "3", "4"], "5"]

Cl.new('splat').run(%w(rgt 1 2 3 4 5))

# Output:
#
#   ["1", "2", ["3", "4", "5"]]

Options

Declaring options can be done by calling the method opt on the class body.

This will add the option, if given by the user, to the hash opts on the Cmd instance. It also defines a reader method that returns the respective value from the opts hash, and a predicate that will be true if the option has been given.

For example:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', 'Target group to add owners to'

  def run
    p opts: opts, to: to, to?: to?
  end
end

Cl.new('owners').run(%w(add --to one))

# Output:
#
#   {:opts=>{:to=>"one"}, :to=>"one", :to?=>true}

Cl.new('owners').run(%w(add --help))

# Output:
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP      Target group to add owners to (type: string)
#     --help          Get help on this command

Options optionally accept a block in case custom normalization is needed.

Depending on the block's arity the following arguments are passed to the block: option value, option name, option type, collection of all options defined on the command.

class Add < Cl::Cmd
  register :add

  # depending on its arity the block can receive:
  #
  # * value
  # * value, name
  # * value, name, type
  # * value, name, type, opts
  opt '--to GROUP' do |value|
    opts[:to] = "group-#{value}"
  end

  def run
    p to: to
  end
end

Cl.new('owners').run(%w(add --to one))

# Output:
#
#   {:to=>"group-one"}

Aliases

Options can have one or many alias names, given as a Symbol or Array of Symbols:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', alias: :group

  def run
    # p opts: opts, to: to, to?: to?, group: group, group?: group?
    p opts: opts, to: to, to?: to?
  end
end

Cl.new('owners').run(%w(add --group one))

# Output:
#
#   {:opts=>{:to=>"one", :group=>"one"}, :to=>"one", :to?=>true}

Defaults

Options can have a default value.

I.e. this value is going to be used if the user does not provide the option:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', default: 'default'

  def run
    p to: to
  end
end

Cl.new('owners').run(%w(add))

# Output:
#
#   {:to=>"default"}

Deprecations

Options, and option alias name can be deprecated.

For a deprecated option:

class Add < Cl::Cmd
  register :add

  opt '--target GROUP', deprecated: 'Deprecated.'

  def run
    p target: target, deprecations: deprecations
  end
end

Cl.new('owners').run(%w(add --target one))

# Output:
#
#   {:target=>"one", :deprecations=>{:target=>"Deprecated."}}

For a deprecated option alias name:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', alias: :target, deprecated: :target

  def run
    p to: to, deprecations: deprecations
  end
end

Cl.new('owners').run(%w(add --target one))

# Output:
#
#   {:to=>"one", :deprecations=>{:target=>:to}}

Downcase

Options can be declared to be downcased.

For example:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', downcase: true

  def run
    p to: to
  end
end

Cl.new('owners').run(%w(add --to ONE))

# Output:
#
#   {:to=>"one"}

Enum

Options can be enums (i.e. have known values).

If an unknown values is given by the user the parser will reject the option, and print the help output for this command.

For example:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', enum: %w(one two)

  def run
    p to: to
  end
end

Cl.new('owners').run(%w(add --to one))

# Output:
#
#   {:to=>"one"}

Cl.new('owners').run(%w(add --to unknown))

# Output:
#
#   Unknown value: to=unknown (known values: one, two)
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP      type: string, known values: one, two
#     --help          Get help on this command

Example

Options can have examples that will be printed in the help output.

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', example: 'group-one'
end

Cl.new('owners').run(%w(add --help))

# Output:
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP      type: string, e.g.: group-one
#     --help          Get help on this command

Format

Options can have a required format.

If a value is given by the user that does not match the format then the parser will reject the option, and print the help output for this command.

For example:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', format: /^\w+$/

  def run
    p to: to
  end
end

Cl.new('owners').run(%w(add --to one))

# Output:
#
#   {:to=>"one"}

Cl.new('owners').run(['add', '--to', 'does not match!'])

# Output:
#
#   Invalid format: to (format: /^\w+$/)
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP      type: string, format: /^\w+$/
#     --help          Get help on this command

Internal

Options can be declared to be internal, hiding the option from the help output.

For example:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP'
  opt '--hidden', internal: true
end

Cl.new('owners').run(%w(add --help))

# Output:
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP      type: string
#     --help          Get help on this command

Min and Max

Options can have mininum and/or maximum values.

If a value is given by the user that does not match the required min and/or max values then the parser will reject the option, and print the help output for this command.

For example:

class Add < Cl::Cmd
  register :add

  opt '--retries COUNT', type: :integer, min: 1, max: 5

  def run
    p retries: retries
  end
end

Cl.new('owners').run(%w(add --retries 1))

# Output:
#
#   {:retries=>1}

Cl.new('owners').run(%w(add --retries 10))

# Output:
#
#   Out of range: retries (min: 1, max: 5)
#
#   Usage: owners add [options]
#
#   Options:
#
#     --retries COUNT      type: integer, min: 1, max: 5
#     --help               Get help on this command

Negations

Flags (boolean options) automatically allow negation using --no-* and --no_* using OptionParser's support for these. However, sometimes it can be convenient to allow other terms for negating an option. Flags therefore accept an option negate like so:

class Add < Cl::Cmd
  register :add

  opt '--notifications', 'Send out notifications to the team', negate: %w(skip)

  def run
    p notifications?
  end
end

Cl.new('owners').run(%w(add --notifications))

# Output:
#
#   true

Cl.new('owners').run(%w(add --no_notifications))

# Output:
#
#   false

Cl.new('owners').run(%w(add --no-notifications))

# Output:
#
#   false

Cl.new('owners').run(%w(add --skip_notifications))

# Output:
#
#   false

Cl.new('owners').run(%w(add --skip-notifications))

# Output:
#
#   false

Note

Options can have a note that will be printed in the help output.

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', note: 'needs to be a group'
end

Cl.new('owners').run(%w(add --help))

# Output:
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP      type: string, note: needs to be a group
#     --help          Get help on this command

Secret

Options can be declared as secret.

This makes it possible for client code to inspect if a given option is secret. Also, option values given by the user will be tainted, so client code can rely on this in order to, for example, obfuscate values from log output.

class Add < Cl::Cmd
  register :add

  opt '--pass PASS', secret: true

  def run
    p(
      secret?: self.class.opts[:pass].secret?,
      tainted?: pass
    )
  end
end

Cl.new('owners').run(%w(add --pass pass))

# Output:
#
#   {:secret?=>true, :tainted?=>true}

Types

Options can have a type. Known types are: :array, :string, :integer, :float, :boolean.

The type :array allows an option to be given multiple times, and makes sure the value accessible on the Cmd instance is a Ruby Array. (This currently only supports arrays of strings).

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', type: :array

  def run
    p to
  end
end

Cl.new('owners').run(%w(add --to one --to two))

# Output:
#
#   ["one", "two"]

Other types cast the given value to the expected Ruby type.

class Add < Cl::Cmd
  register :add

  opt '--active BOOL', type: :boolean
  opt '--retries INT', type: :integer
  opt '--sleep FLOAT', type: :float

  def run
    p active: active.class, retries: retries.class, sleep: sleep.class
  end
end

Cl.new('owners').run(%w(add --active yes --retries 1 --sleep 0.1))

# Output:
#
#   {:active=>TrueClass, :retries=>Integer, :sleep=>Float}

Required Options

There are three ways options can be required:

using required: true on the option: the option itself is required to be given
using requires: :otheron the option: the option requires another option to be given
using required :one, [:two, :three] on the class: either one or both two and three must be given

For example, this simply requires the option --to:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP', required: true

  def run
    p to: to
  end
end

Cl.new('owners').run(%w(add --to one))

# Output:
#
#   {:to=>"one"}

Cl.new('owners').run(%w(add))

# Output:
#
#   Missing required option: to
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP      type: string, required
#     --help          Get help on this command

This will make the option --retries depend on the option --to:

class Add < Cl::Cmd
  register :add

  opt '--to GROUP'
  opt '--other GROUP', requires: :to

  def run
    p to: to, other: other
  end
end

Cl.new('owners').run(%w(add --to one --other two))

# Output:
#
#   {:to=>"one", :other=>"two"}

Cl.new('owners').run(%w(add --other two))

# Output:
#
#   Missing option: to (required by other)
#
#   Usage: owners add [options]
#
#   Options:
#
#     --to GROUP         type: string
#     --other GROUP      type: string, requires: to
#     --help             Get help on this command

This requires either the option --api_key or both options --username and --password to be given:

class Add < Cl::Cmd
  register :add

  # read DNF, i.e. "token OR user AND pass
  required :token, [:user, :pass]

  opt '--token TOKEN'
  opt '--user NAME'
  opt '--pass PASS'

  def run
    p token: token, user: user, pass: pass
  end
end

Cl.new('owners').run(%w(add --token token))

# Output:
#
#   {:token=>"token", :user=>nil, :pass=>nil}

Cl.new('owners').run(%w(add --user user --pass pass))

# Output:
#
#   {:token=>nil, :user=>"user", :pass=>"pass"}

Cl.new('owners').run(%w(add))

# Output:
#
#   Missing options: token, or user and pass
#
#   Usage: owners add [options]
#
#   Options:
#
#     Either token, or user and pass are required.
#
#     --token TOKEN      type: string
#     --user NAME        type: string
#     --pass PASS        type: string
#     --help             Get help on this command

Config Files

Cl automatically reads config files that match the given executable name (inspired by gem-release), stored either in the user directory or the current working directory.

For example:

module Api
  class Login < Cl::Cmd
    opt '--username USER'
    opt '--password PASS'
  end
end

# bin/api
CL.new('api').run(ARGV)

# ~/api.yml
login:
  username: 'someone'
  password: 'password'

# ./api.yml
login:
  username: 'someone else'

then running

$ bin/api login

instantiates Api::Login, and passes the hash

{ username: 'someone else', password: 'password' }

as opts.

Options passed by the user take precedence over defaults defined in config files.

Environment Variables

Cl automatically defaults options to environment variables that are prefixed with the given executable name (inspired by gem-release).

module Api
  class Login < Cl::Cmd
    opt '--username USER'
    opt '--password PASS'
  end
end

# bin/api
CL.new('api').run(ARGV)

then running

$ API_USERNAME=someone API_PASSWORD=password bin/api login

instantiates Api::Login, and passes the hash

{ username: 'someone', password: 'password' }

Options passed by the user take precedence over defaults given as environment variables, and environment variables take precedence over defaults defined in config files.

Cl

Table of Contents

Basic Usage

Command Registry

Runners

Command DSL

Commands

Description, Summary, Examples

Abstract

Arguments

Types

Splat

Options

Aliases

Defaults

Deprecations

Downcase

Enum

Example

Format

Internal

Min and Max

Negations

Note

Secret

See Also

Types

Required Options

Config Files

Environment Variables