argv.js

Simple argv parser

Motivation

I needed a new argv parser for a quick and dirty project I was working on and evaluating and selecting the proper existing parser and then learning its API, quirks and adapting the architecture to it seemed to be more complicated, require more effort and far less fun than putting together a trivial parser myself in a couple of hours.
This code is an evolution of that parser.

Features

• Simple
• Supports both the option (a-la ls) and command (a-la git) paradigms
• Nestable
  parsers can be nested as option/command handlers defining independent nested contexts
• Option expansion
  -abc expands to -a -b -c if -abc is not defined
• Option/command value passing
  implicit -a 123 (requires definition or manual handling) or explicit -a=123
• Environment variable option/command value defaults
• Option/command value conversion
• Option/command value collection
• Multiple option prefix support
• Reasonable defaults:
  • -help – generate and print help
  • -version – print version
  • -quiet – suppress printing
  • - – stop argument processing
• Extensible:
  • Hooks for dynamic option/command handling
  • Customizable error and stop condition handling

Planned Features

• Run <command>-<sub-command> scripts
• Option doc grouping (???)

Contents

• argv.js
  • Motivation
  • Features
  • Planned Features
  • Contents
  • Architecture
  • Installation
  • Basics
  • Options in more detail
    • Help and metadata
    • Basic options
    • Commands
    • Active options/commands
    • Nested parsers
    • Stopping
    • Error reporting
    • Calling the script
  • Advanced docs
  • More...
  • License

Architecture

	Parser(..) -> <parser> -> <parsed>

This module provides the following workflow:

• define/declare a parser (parse grammar)

  Parser(<spec>)
  	-> <parser>
  

• define post-parse callbacks (optional)

  <parser>
  	.then(<callback>)
  	.stop(<callback>)
  	.error(<callback>)
  

• parse

  <parser>(...)
  	-> <parsed>
  

  • option handlers defined in <spec> are called while parsing,
  • the appropriate <callback>s are called after the <parser> is done,
  • everything is run in the context of the <parsed> object so any data set on it is accessible after parsing is done for further reference.

Note that the <parser> is fully reusable and on each call will produce a new <parsed> object.

The <parsed> object has the <parser> as its .__proto__.

Installation

$ npm install ig-argv

Basics

Create a script and make it runnable

$ touch script.js
$ chmod +x script.js

Now for the code

#!/usr/bin/env node

// compatible with both node's and RequireJS' require(..)
var argv = require('ig-argv')

var parser = argv.Parser({
		// option definitions...
		// ...
	})
	.then(function(){
		// things to do after the options are handled...
		// ...
	})

// run the parser...
__filename == require.main
	&& parser(process.argv)

This will already create a script that can respond to -help and freinds.

$ ./script.js --help 

Options in more detail

Let us populate the option definitions splitting the job into sections.

Start by creating a parser...

var parser = argv.Parser({

Help and metadata

Basic script description

	doc: 'Example script options',

Metadata:

	// to make things consistent we'll take the version from package.json
	version: require('./package.json').version,

	author: 'John Smith <j.smith@some-mail.com>',
	license: 'BSD-3-Clause',

These basic bits of metadata can be referenced in other -help sections, for example:

	footer: 'Written by $AUTHOR ($VERSION / $LICENSE).',

Basic options

These, if encountered, simply assign a value to an attribute on the parsed object.

If no value is given true is assigned to indicate that the option/command is present in the command-line.

	'-bool': {
		doc: 'if given set .bool to true' },


	// option with a value...
	'-value': {
		doc: 'set .x to X',

		// 'X' (VALUE) is used for -help while 'x' (key) is where the 
		// value will be written...
		arg: 'X | x',

		// the value is optional by default but we can make it required...
		valueRequired: true,
	},


	// setup an alias -r -> -required
	'-r': '-required',

	// a required option...
	'-required': {
		doc: 'set .required_option_given to true'

		// NOTE: we can omit the VALUE part to not require a value...
		// NOTE: of no attr is specified in arg option name is used.
		arg: '| required_option_given',

		required: true,

		// keep this near the top of the options list in -help...
		priority: 80,
	},


	'-int': {
		doc: 'pass an integer value',

		// NOTE: if not key is given the VALUE name is used as a key, so the 
		// 		value here is assigned to .INT...
		arg: 'INT',

		// convert the input value to int...
		type: 'int',
	},
	

	'-default': {
		doc: 'option with default value',
		arg: 'VALUE | default',

		default: 'some value',
	},


	'-home': {
		doc: 'set home path',
		arg: 'HOME | home',

		// get the default value from the environment variable $HOME...
		env: 'HOME',
	},

	
	// collecting values...
	'-p': '-push',
	'-push': {
		doc: 'push elements to a .list',
		arg: 'ELEM | list',

		// this will add each argument to a -push option to a list...
		collect: 'list',
	},

Commands

The only difference between an option and a command is the prefix ("-" vs. "@") that determines how it is parsed, otherwise they are identical and everything above applies here too.

	'@command': {
		// ...
	},

	// Since options and commands are identical, aliases from one to the 
	// other work as expected...
	'-c': '@command',

Active options/commands

These define .handlers which are executed when the option is encountered by the parser

	'-active': {
		doc: 'basic active option',
		handler: function(args, key, value){
			// ...
		} },

And for quick-n-dirty hacking stuff together, a shorthand (not for production use):

	'-s': '-shorthand-active',
	'-shorthand-active': function(args, key, value){
		// ...
	},

Nested parsers

An options/command handler can also be a full fledged parser.

	'@nested': argv.Parser({
			// ...
		}).then(function(){
			// ...
		}),

This can be useful when there is a need to define a sub-context with it's own options and settings but it does not need to be isolated into a separate external command.

When a nested parser is started it will consume subsequent arguments until it exits, then the parent parser will pick up where it left.

Externally it is treated in exactly the same way as a normal function handler, essentially, the parent parser does not know the difference between the two.

For more detail see the Nested parsers section in detailed docs.

Stopping

To stop option processing either return STOP or THEN from the handler.

• THEN is the normal case, stop processing and trigger <parser>.then(..):

  	'-then': { 
  		handler: function(){
  			return argv.THEN } },
  

• STOP will stop processing and trigger <parser>.stop(..):

  	'-stop': { 
  		handler: function(){
  			return argv.STOP } },
  

Error reporting

There are three ways to stop and/or report errors:

• Simply throw a ParserError(..) instance:

  	'-error': {
  		handler: function(){
  			throw argv.ParserError('something went wrong.') } },
  

  Here processing will stop and the error will be reported automatically before <parser>.error(..) is triggered.

• Silently return a ParserError(..) instance:

  	'-silent-error': {
  		handler: function(){
  			return argv.ParserError('something went wrong.') } },
  

  This will not report the error but will stop processing and trigger <parser>.error(..), so the user can either recover from or report the issue manually.

• For a critical error simply throw any other JavaScript error/exception:

  	'-critical-error': {
  		handler: function(){
  			throw 'something went really wrong.' } },
  
  // and to close things off ;)
  })
  

Note that <parser>.then(..) will not be triggered in any of these cases.

Also see: <parser>.printError(..)

Calling the script

This will create a parser that supports the following:

$ ./script.js --help 

$ ./script.js --value 321

$ ./script.js --value=321

$ ./script.js command

$ ./script.js nested -h

$ ./script.js -fb

Advanced docs

For a more detailed set of docs see ADVANCED.md

More...

For more info see the source.

License

BSD 3-Clause License

Copyright (c) 2016-2020, Alex A. Naanou,
All rights reserved.