clap — Command line argument parser for Pharo

Named after and inspired by clap-rs, but this is an independent implementation.

Currently still in the initial implementation phase, meaning the main pieces are there but many features are still missing and may force changes in the design.

Loading instructions

starting from a Pharo image

Metacello new baseline: 'Clap';
    repository: 'github://cdlm/clap-st/src';
    load.

starting from the shell

git clone https://github.com/cdlm/clap-st.git
cd clap-st
curl get.pharo.org/alpha+vm | bash

…and then, in the image just downloaded, open a workspace and evaluate:

Metacello new baseline: 'Clap';
   repository: 'gitlocal://./src';
   load.

Shameless plug: I work with Fari and direnv to automate building and launching the development image:

# setup $PHARO
fari build
fari run

Defining and invoking commands

Commands and subcommands are instances of ClapCommand. To make a command accessible from the command line, return it from a class-side factory method with the <commandline> pragma. For instance, here's how we declare the traditional hello, world! example, with the actual behavior delegated the instance-side method ClapCommandLineExamples >> sayHello:

hello
	"The usual Hello-World example, demonstrating a Clap command with a couple options."
	<commandline>

	^ (ClapCommand withName: 'hello')
		description: 'Provides greetings';
		add: ClapFlag forHelp;
		add: ((ClapFlag withName: 'shout')
			description: 'Greet loudly');
		add: ((ClapPositional withName: 'who')
			description: 'Recipient of the greetings';
			defaultMeaning: [ 'world' ]);
		meaning: [ :args |
			args atName: 'help' ifFound: [ :help |
				help value.
				help context exitSuccess ].

			(self with: args) sayHello ]

For now, Clap installs itself as a named command line handler; e.g., to run the hello example command:

$PHARO_VM $PHARO_IMAGE clap hello
$PHARO_VM $PHARO_IMAGE clap hello --shout you

Commands can also be tested from within the image; running them from an interactive session will not quit the image, but any output from the command will still go to the standard output:

ClapCommandLineExamples hello
	runWith: #('hello' '--help').

Contributors

Many thanks to everyone who has contributed to clap in one way or another:

Clément Mastin, Damien Pollet, Rajula Vineet Reddy