Unlike other argument parsers, this library is built specifically (and only) for positional arguments, allowing it to provide much more functionality and control over how positional arguments are interpreted. It also doesn't force you to restructure your code to use it. All the individual pieces are exposed and work standalone, so you only have to use as much of the library as you need.

This library was originally written to be a lightweight, unintrusive alternative to Commando for Discord bots. There are no Discord-specific things in this library, but it does still work well for this purpose.

Features:

• No external dependencies.
• Lightweight, unintrusive API that doesn't change the paradigm of your code.
• Each class of the library is exposed, so you can use as much or as little as you want.
• Parses from strings or arrays from any source.
• Validate and transform arguments with user-specified functions.
• Provides parsed arguments in a format similar to other argparse libraries, such as yargs.
• Define commands with multiple argument lists and auto-generated help text.
• Command registry can consume a command string and delegate it to the appropriate command.
• Async / Promise friendly. All user-specified functions may be async.
• Useful alternative to Commando.js for Discord bots.

Available on npm.

npm install positional-args

See full API here!

See GitHub releases page for API changes.

This example creates a CommandRegistry with multiple commands and handler for unrecognized commands.

const registry = new CommandRegistry()
    .add(new Command('say')
        .description('Prints the args given. Also has multiple argument sets, for fun')
        .addArgSet([ new Argument('first') ])
        .addArgSet([
            new Argument('first'),
            new Argument('extras')
                .varargs(true)
                .optional(true),
        ])
        .handler(args => console.log('I got', args))
    )
    .add(new Command('die_always')
        .description('I always throw because I am not nice')
        .handler(() => { throw new Error('I strike again!') })
    )
    .helpHandler() // Use the built-in help handler
    .defaultHandler((parts) => console.log('Unrecognized command', parts));

registry.help('say'); /* Returns string:
"say <first>\n" +
"say <first> <extras_1> [extras_2] ... [extras_n]" */

registry.execute('say one'); /* Prints:
I got {
  _: ["one"],
  first: "one",
} */

registry.execute('say one two three four'); /* Prints:
I got {
  _: ["one", "two", "three", "four"],
  first: "one",
  extras: ["two", "three", "four"],
} */

try {
    registry.execute('die_always');
} catch (err) {
    // CommandError
    // .message: "Command failed"
    // .nested: Error("I strike again!")
    // .full_message: "Command failed: I strike again!"
}

registry.execute('some random thing'); /* Prints:
Unrecognized command ["some", "random", "thing"] */

There are more examples in the API docs.

This library has a permissive enough API that one could force mixing sync and async elements together. While this is possible, it is explicitly discouraged and not officially supported. If you need both sync and async commands, consider either making all commands async or dividing them into two separate registries.

// DON'T DO THIS!
const registry = new CommandRegistry()
    .asynchronous(false)
    .add(new Command('example'))
    .add(new Command('other'));
registry.commands.get('example').is_async = true;

try {
    registry.execute('example').then(...).catch(...);
} catch (err) {
    ...
}

// Do this instead!
const registry = new CommandRegistry()
    .asynchronous(true)
    .add(new Command('example'))
    .add(new Command('other'));

registry.execute('example').then(...).catch(...);

Copyright 2021 Mimickal

This code is licensed under the LGPL-3.0 license.

Basically, you are free to use this library in your closed source projects, but any modifications to this library must be made open source.