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--arguable

Arguable is a command line parser that lends structure to your command line programs. You can use Arguable as a simple command line parser, or you can use it to organize your program in a master program with any number of sub-commands in the style of git, apt-get or yum.

Usage First

Arguable starts with your usage message. It extracts the program arguments from the usage message. Arguable compels you to write a usage message in order to get your command line to parse.

#!/usr/bin/env node

/*

  ___ usage: en_US ___
  usage: frobinate [options] [file...] [file]

  options:

  -h, --help                  display this message
  -p, --processes   [count]   number of processes to run in parallel

  description:

  frobinate will reticuatle the splines in all of your transmogrifier
  files, optionally in parallel. The `--processes` option is the number
  of processes to run concurrently, defaulting to one.

  ___ usage ___

*/

require('arguable')(__filename, function (options) {
  if (options.help) throw new Error("usage");
  require('../lib/frobinator').frobinate(options.processes, options.$argv);
});

In the spirit of opinionated software Arguable starts with a full help message, because I believe that a full usage message is important for a command line program.

Usage messages are important to Node.js; Linux users have become accustomed to having a lot of context at their disposal when they invoke --help. Windows users are without a decent manual page system, so they tend to rely on usage messages to discover what their software can do.

I don't want my command line library to assemble a usage message from a method chained, declarative API. The usage message and arguments of a command line program are the user interface. I do not expect its implementation to be trivial. I do not want to delegate the details to a module.

It would rather have spend time composing a nicely formatted usage message, with the ability to see the whole message, then work from that message.

Anatomy of a Usage Message

Your usage message must contain a long option for every option; short options are optional.

If you have a synonym for one of your commands, simply declare it separately and document it separately.

The only argument validation that Arguable* performs is to check that arguments that accept a parameter have a parameter; that arguments that don't accept a parameter don't have a parameter. Type checking is meant to be performed by the program itself.

#!/usr/bin/env node

/*

  ___ usage: en_US ___
  usage: frobinate [options] [file...] [file]

  options:

  -h, --help                  display this message
  -p, --processes   [count]   number of processes to run in parallel
  -t, --threads     [count]   same as `--proceses`
  -v, --verbose               toggle verbose output

  description:

  frobinate will reticuatle the splines in all of your transmogrifier
  files, optionally in parallel. The `--processes` option is the number
  of processes to run concurrently, defaulting to one.

  ___ usage ___

*/

require('arguable')(__filename, function (options) {
  if (options.params.help) throw new Error("usage");
  var processes = options.processes || options.threads || 1;
  require('../lib/frobinator').frobinate(processes, options.verbose, options.$argv);
});

TK: Add an example of type checking — integer — to the example above.

TK: The error checking example would also show how to report errors.

TK: End of last edit.

Commands with Sub-Commands

Arguable allows you to specify sub-commands in the style of git, apt-get or yum. Add the sub-command name to your usage description. Arguable will select the correct help message based on the program arguments.

/*

  ___ run _ usage: en_US ___
  usage: frobinate run [options] [file...] [file]

  options:

  -h, --help                  display this message
  -p, --processes     [count] number of processes to run in parallel

  description:

  frobinate will reticuatle the splines in all of your transmogrifier
  files, optional in parallel. The `--processes` option is the number of
  processes to run concurrently, defaulting to zero.

  ___ compile _ usage: en_US ___
  usage: frobinate compile [options] [file...] [file]

  options:

  -h, --help                  display this message
  -s, --strict                strict interpretation of the ISO 33465
                              Frobination Standard.
  -p, --prefix                prefix for frobination identifiers

  description:

  `frobinate compile` will accelerate frobination by compling it to
  intermediate output interpreted code (IOIC) then frobinating the hell
  out it.

  ___ usage ___

*/

var arguable = require('arguable')
  , frobinator = require('../lib/frobinator')
  , icoc
  ;

arguable(__filename, function (options) {
  if (options.help) options.abend();
  switch (options.command) {
  case 'compile':
    ioic = frobinator.prepare(options.strict, option.prefix, options.$argv);
    frobinator.frobinator(ioic);
    break
  case 'run':
    frobinator.frobinate(options.processes, options.$argv);
    break;
  default:
    abend('unknown command', e.usage);
  }
});

Internationalization

Arguable supports internationalization. Simply write additional usage messages in other languages following the default language, marking the additional languages with their locale string. You can then invoke the parser passing the current locale string as the first argument.


/*

___ usage: en_US ___
usage: awaken

  Good morning!
___ usage: fi_FI ___
käyttö: awaken

  Hyvää huomenta!
___ usage ___

*/

var parse = require('arguable').parse
  , options = parse(process.env.lang, __filename, []);

console.log(options.$usage);

We can run the above program with our LANG environment variable set to one of the supported languages.

$ LANG=fi_FI.UTF-8 node awaken.js
käyttö: awaken

  Hyvää huomenta!

The above will print the Finnish version of the help message. You can pass the language specified in the users LANG environment variable directly to parse. If no such language translation exists, it falls back to the first translation encountered.

Note that command names and switches are not internationalized. Changing the user's language preferences is not supposed change the program interface.

Error Messages

You can define internationalized error messages. Add a strings section to following your usage defintion

#!/usr/bin/env node

/*

  ___ usage: en_US ___
  usage: frobinate [options] [file...] [file]

  options:

  -h, --help                  display this message
  -p, --processes   [count]   number of processes to run in parallel

  description:

  frobinate will reticuatle the splines in all of your transmogrifier
  files, optionally in parallel. The `--processes` option is the number
  of processes to run concurrently, defaulting to one. Note that you
  cannot run more than four processes at time.

  ___ strings ___

    too many processes:
      You choose %d processes to frobinate %s, but the maximum is 4.

  ___ usage ___

*/

require('arguable')(__filename, function (options) {
  if (options.help) throw new Error("usage");
  if (options.processes > 4) {
    options.abend('too many processes', options.processes, options.argv[0]);
  }
  require('../lib/frobinator').frobinate(options.processes, options.argv);
});

Arguments are fed to util.format and the result is printed in your language message to standard out.

Each language can have it's own message section. Your translation might need to reorder the arguments to fit a different sentence structure. Here's an example of reordering, however we're still in English, because it's really all I know.

Oh, I'd love a patch if you have an example in your language, and your language is not English.

#!/usr/bin/node

/*

  ___ usage: en_US ___
  usage: frobinate [options] [file...] [file]

  options:

  -h, --help                  display this message
  -p, --processes   [count]   number of processes to run in parallel

  description:

  frobinate will reticuatle the splines in all of your transmogrifier
  files, optionally in parallel. The `--processes` option is the number
  of processes to run concurrently, defaulting to one. Note that you
  cannot run more than four processes at time.

  ___ strings ___

    too many processes (2, 1):
      You choose frobinate %s using %d processes, but the maximum is 4.

  ___ usage ___

*/

require('arguable')(__filename, function (options) {
  if (options.help) throw new Error("usage");
  if (options.processes > 4) {
    options.abend('too many processes', options.processes, options.argv[0]);
  }
  require('../lib/frobinator').frobinate(options.processes, options.argv);
});

The Fatal Callback

Your appliation may want to report an error through Arguable after the initial Arguable callback has completed. It is often the case in Node.js that it only gets interesting after you've invoked a few callbacks.

When you plan on using help or abend in a callback, you're going to want to make sure that the error propagates out to the fatal function of the options object.

TK: LOL! Domains! I was such a good boy trying to entertain everyone else's feeble stab at control-flow.

How you propagate your errors is up to you. Here we use the "domain" package to propagte errors.

#!/usr/bin/node

/*

  ___ usage: en_US ___
  usage: frobinate [options]

  options:

  -h, --help                  display this message
  -p, --processes   [count]   number of processes to run in parallel
  -f, --file        [path]    the file to frobinate

  description:


  frobinate will reticuatle the splines in all of your transmogrifier
  files, optionally in parallel. The `--processes` option is the number
  of processes to run concurrently, defaulting to one. Note that you
  cannot run more than four processes at time. The `--file` option is path to
  the file to frobinate and it is required.

  ___ strings ___

    too many processes (2, 1):
      You choose frobinate %s using %d processes, but the maximum is 4.

    file missing:
      cannot find the file to frobinate: %s.

  ___ usage ___

*/

require('arguable')(__filename, function (options) {
  var d = require('domain').create();
  d.on('error', options.fatal);
  d.run(function () {
    var fs = require('fs');

    if (options.help) options.help();

    if (options.processes > 4) {
      options.abend('too many processes', options.processes, options.argv[0]);
    }

    // Read a file.
    fs.readFile(options.file, d.intercept(function (result) {
      // Here we either call abend or rethrow the error, either way we'll
      // propagate to our `options.fatal` function..
      if (error) {
        if (error.code == 'ENOENT') options.abend('file missing', options.file);
        else throw error;
      }
      // Good to go.
      require('../lib/frobinator').frobinate(options.processes, options.argv);
    }));
  });
});

You could use process.on("uncaughtException") for a quicker and dirtier implementation that would work just as well.

Contributors

Change Log

todo: Move this into GitHub Releases?

Changes for each release.

Version 0.0.9

Sun Jun 30 14:57:25 UTC 2013

Version 0.0.8

Thu Mar 21 05:26:43 UTC 2013

Version 0.0.7

Thu Feb 28 07:23:51 UTC 2013

Version 0.0.6

Thu Feb 21 07:42:25 UTC 2013

Version 0.0.5

Tue Jul 10 19:02:23 UTC 2012

Version 0.0.4

Tue Jul 10 05:32:25 UTC 2012

Version 0.0.3

Mon Jul 9 18:24:28 UTC 2012

Version 0.0.2

Mon Jul 9 00:19:49 UTC 2012

Version 0.0.1

Sun Jul 8 23:29:58 UTC 2012

Version 0.0.0

Sun Jul 8 02:53:58 UTC 2012