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https://github.com/ioquatix/samovar


https://github.com/ioquatix/samovar

documentation-generator nested-commands option-parser parsing ruby

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README 

        
# Samovar



![Teapot](teapot.png)



Samovar is a modern framework for building command-line tools and applications. It provides a declarative class-based DSL for building command-line parsers that include automatic documentation generation. It helps you keep your functionality clean and isolated where possible.



[![Development Status](https://github.com/ioquatix/samovar/workflows/Test/badge.svg)](https://github.com/ioquatix/samovar/actions?workflow=Test)



## Motivation



I've been using [Optimist](https://github.com/ManageIQ/optimist) and while it's not bad, it's hard to use for sub-commands in a way that generates nice documentation. It also has pretty limited support for complex command lines (e.g. nested commands, splits, matching tokens, etc). Samovar is a high level bridge between the command line and your code: it generates decent documentation, maps nicely between the command line syntax and your functions, and supports sub-commands using classes which are easy to compose.



One of the other issues I had with existing frameworks is testability. Most frameworks expect to have some pretty heavy logic directly in the binary executable, or at least don't structure your code in a way which makes testing easy. Samovar structures your command processing logic into classes which can be easily tested in isolation, which means that you can mock up and [spec your command-line executables easily](https://github.com/ioquatix/teapot/blob/master/spec/teapot/command_spec.rb).



## Examples



  - [Teapot](https://github.com/ioquatix/teapot/blob/master/lib/teapot/command.rb) is a build system and uses multiple top-level commands.

  - [Utopia](https://github.com/ioquatix/utopia/blob/master/lib/utopia/command.rb) is a web application platform and uses nested commands.

  - [Synco](https://github.com/ioquatix/synco/blob/master/lib/synco/command.rb) is a backup tool and sends commands across the network and has lots of options with default values.



## Installation



Add this line to your application's Gemfile:



    gem 'samovar'



And then execute:



    $ bundle



Or install it yourself as:



    $ gem install samovar



## Usage



Generally speaking, you should create `Command` classes that represent specific functions in your program. The top level command might look something like this:



``` ruby

require 'samovar'



class List < Samovar::Command

	self.description = "List the current directory"

	

	def call

		system("ls -lah")

	end

end



class Application < Samovar::Command

	options do

		option '--help', "Do you need help?"

	end

	

	nested :command, {

		'list' => List

	}, default: 'list'

	

	def call

		if @options[:help]

			self.print_usage

		else

			@command.call

		end

	end

end



Application.call # Defaults to ARGV.

```



### Basic Options



``` ruby

require 'samovar'



class Application < Samovar::Command

	options do

		option '-f/--frobulate ', "Frobulate the text"

		option '-x | -y', "Specify either x or y axis.", key: :axis

		option '-F/--yeah/--flag', "A boolean flag with several forms."

		option '--things ', "A list of things" do |value|

			value.split(/\s*,\s*/)

		end

	end

end



application = Application.new(['-f', 'Algebraic!'])

application.options[:frobulate] # 'Algebraic!'



application = Application.new(['-x', '-y'])

application.options[:axis] # :y



application = Application.new(['-F'])

application.options[:flag] # true



application = Application.new(['--things', 'x,y,z'])

application.options[:things] # ['x', 'y', 'z']

```



### Nested Commands



``` ruby

require 'samovar'



class Create < Samovar::Command

	def invoke(parent)

		puts "Creating"

	end

end



class Application < Samovar::Command

	nested '',

		'create' => Create

	

	def invoke(program_name: File.basename($0))

		if @command

			@command.invoke

		else

			print_usage(program_name)

		end

	end

end



Application.new(['create']).invoke

```



### ARGV Splits



``` ruby

require 'samovar'



class Application < Samovar::Command

	many :packages

	split :argv

end



application = Application.new(['foo', 'bar', 'baz', '--', 'apples', 'oranges', 'feijoas'])

application.packages # ['foo', 'bar', 'baz']

application.argv # ['apples', 'oranges', 'feijoas']

```



### Parsing Tokens



``` ruby

require 'samovar'



class Application < Samovar::Command

	self.description = "Mix together your favorite things."

	

	one :fruit, "Name one fruit"

	many :cakes, "Any cakes you like"

end



application = Application.new(['apple', 'chocolate cake', 'fruit cake'])

application.fruit # 'apple'

application.cakes # ['chocolate cake', 'fruit cake']

```



### Explicit Commands



Given a custom `Samovar::Command` subclass, you can instantiate it with options:



``` ruby

application = Application['--root', path]

```



You can also duplicate an existing command instance with additions/changes:



``` ruby

concurrent_application = application['--threads', 12]

```



These forms can be useful when invoking one command from another, or in unit tests.



## Contributing



We welcome contributions to this project.



1.  Fork it.

2.  Create your feature branch (`git checkout -b my-new-feature`).

3.  Commit your changes (`git commit -am 'Add some feature'`).

4.  Push to the branch (`git push origin my-new-feature`).

5.  Create new Pull Request.



### Developer Certificate of Origin



This project uses the [Developer Certificate of Origin](https://developercertificate.org/). All contributors to this project must agree to this document to have their contributions accepted.



### Contributor Covenant



This project is governed by the [Contributor Covenant](https://www.contributor-covenant.org/). All contributors and participants agree to abide by its terms.



## Future Work



### Multi-value Options



Right now, options can take a single argument, e.g. `--count `. Ideally, we support a specific sub-parser defined by the option, e.g. `--count ` or `--tag  `. These would map to specific parsers using `Samovar::One` and `Samovar::Many` internally.



### Global Options



Options can only be parsed at the place they are explicitly mentioned, e.g. a command with sub-commands won't parse an option added to the end of the command:



``` ruby

command list --help

```



One might reasonably expect this to parse but it isn't so easy to generalize this:



``` ruby

command list -- --help

```



In this case, do we show help? Some effort is required to disambiguate this. Initially, it makes sense to keep things as simple as possible. But, it might make sense for some options to be declared in a global scope, which are extracted before parsing begins. I'm not sure if this is really a good idea. It might just be better to give good error output in this case (you specified an option but it was in the wrong place).



### Shell Auto-completion



Because of the structure of the Samovar command parser, it should be possible to generate a list of all possible tokens at each point. Therefore, semantically correct tab completion should be possible.



As a secondary to this, it would be nice if `Samovar::One` and `Samovar::Many` could take a list of potential tokens so that auto-completion could give meaningful suggestions, and possibly improved validation.



### Short/Long Help



It might be interesting to explore whether it's possible to have `-h` and `--help` do different things. This could include command specific help output, more detailed help output (similar to a man page), and other useful help related tasks.