Yaclap

Yet another command line argument parser for Nim.

Example

import yaclap

var app = newApp("MyApp")[]
  .version("1.0")
  .author("John Doe <example@email.com>")
  .about("Does awesome things")
  .arg(
    newArg("config")
    .short("-c")
    .long("--config")
    .help("Sets a custom config file")
    .takes_value(true)
  )
  .arg(
    newArg("output")
    .help("Sets an optional output file")
    .index(1)
  )
  .arg(
    newArg("debug")
    .short("-d")
    .multiple(true)
    .help("Turn debugging information on")
  )
  .subcommand(
    newSubCommand("test")
    .about("Has test sub functionality")
    .arg(
      newArg("quiet")
      .short("-q")
      .help("Display less verbose information")
    )
  )

var matches = app.get_matches()

if letSome(o, matches.value_of("output")):
  echo("Value for output: ", o)

if letSome(c, matches.value_of("config")):
  echo("Value for config: ", c)

case matches.occurrences_of("debug")
of 0: echo("Debug mode is off")
of 1: echo("Debug mode is kind of on")
of 2: echo("Debug mode is on")
else: echo("Don't be crazy")

if letSome(matches, matches.subcommand_matches("test")):
  if matches.is_present("quiet"):
    echo("Printing quieter test info...")
  else:
    echo("Printing verbose test info...")

See also

Other Nim command-line argument parsers:

• std/parseopt
• cligen
• argparse
• therapist
• docopt
• commandant
• clapfn
• nclap

Goals and Design

There were already a lot of command-line argument parsers for Nim, but foremost what I wanted is something as featureful and as declarative as possible because these are the kind of modern parsers that seem to be the most popular in other languages nowadays, like C++'s argparse, Rust's clap, Zig's clap, JavaScript's commander, etc.

Nim's unofficial motto is "Copying bad design is not good design", and as so I've looked at several of these parsers and decided that Rust's clap was a good building block to then polish to fit Nim's style. To that end, the rough steps for this project are:

1. Port and get as many features from Rust's clap's "builder API" as we can
2. Add a simpler and more Nim-like API (maybe with named arguments + templates like Nim's argparse)
3. Add features that are still not in Rust's clap, like option prefixes
4. Simplify the API even more (maybe by parsing strings) and we'll go from there

Licence

MIT