cli-belt

An utility belt to complement your arguments parser of choice.

Install

npm install cli-belt

Motivation

Most solutions for creating command line interfaces have a too high degree of magic going on that prevents proper control over how arguments are parsed, which arguments are parsed, and so on. On the other hand, using barebones argument parsers can require much boilerplate. cli-belt intends to complement the later, reducing the amount of boilerplate needed. I've found arg to be a blissful middle ground for argument parsing, but which parser you use is entirely up to you.

Documentation

These are all of cli-belt's helper functions -see docs:

• loadPackage finds and returns the contents of the first package.json found, recursing up from a dir.
• flags parses a help string and returns an object with options, aliases, arguments, and descriptions.
• safePairs ensures all properties of an object exist in another.
• splitBy splits an arguments array into two arrays by the first separator.
• error formats and prints an error message, optionally exiting the process.

Usage example

import { loadPackage, flags, safePairs, splitBy, error } from 'cli-belt';
import { stripIndent as indent } from 'common-tags';
import arg from 'arg';
import logger from 'loglevel';
import spawn from 'await-spawn';

main().catch((err) => error(err, { exit: 1, debug: true, logger }));

export default async function main() {
  // Get description and version from `package.json`
  const pkg = await loadPackage(__dirname, { title: true });

  const help = indent`
    ${pkg.description || ''}

    Usage: example [options] -- [echoArgs]

    Options:
      -e, --env <environment>    Node environment
      -h, --help                 Show help
      -v, --version              Show version number

    Examples:
      $ example -v
      $ example --help
      $ example -- "this will get printed because we're spawning echo"
  `;

  // Get flags and aliases from help
  const { options, aliases } = flags(help);

  // Define option types
  const types = {
    '--env': String,
    '--help': Boolean,
    '--version': Boolean
  };

  // Ensure all parsed flags have a defined type,
  // and that they have all been successfully parsed and exist on help
  safePairs(types, options, { fail: true, bidirectional: true });

  // Add aliases to the ones explicitly typed
  Object.assign(types, aliases);

  // Only pass to `arg` arguments before '--'
  // arguments after '--' will be passed to spawn
  const [argv, args] = splitBy(process.argv.slice(2), '--');
  const cmd = arg(types, {
    argv,
    permissive: false,
    stopAtPositional: true
  });

  // Handle options
  if (cmd._.length) throw Error(`Unknown command ${cmd._[0]}`);
  if (cmd['--help']) return console.log(help);
  if (cmd['--version']) return console.log(pkg.version);

  const env = cmd['--env'] ? { NODE_ENV: cmd['--env'] } : {};
  await spawn('echo', args, { env, stdio: 'inherit' });
}