README.md

SYNOPT

Command line options package with narrow scope and ease of use.

Core Ideas

• easy to declare options and flags
• parse command line arguments into option map
• generate usage banner automatically
• don't ever call exit to ease testing

More Features

• support boolean options (flags)
• support repeat options (-n first -n second,third to ["first", "second", "third"])
• long and short option names (e.g. -s, --long)
• use = for long format option value (--name=val)
• append value to short format option (-nval)
• no assumptions about defaults (leave room for config files, and env vars)
• no assumptions about subcommands (but easy to accomodate)
• explicit failure result instead of exceptions
• full Typescript
• zero dependencies

Example Usage

import synopt from "synopt";

// Declare options
synopt
  .name("mkwebmanifest") // optional, for usage banner
  .summary("Generate icons and web manifest for web applications")
  .option("-i", "--icon ICON", "source icon file")
  .option("-n", "--name", "name of the web application", { repeat: true })
  .option("--config FILE", "configuration file")
  .option("--outdir <directory>", "directory path for generated files")
  .option("--verbose", "more output", { boolean: true })
  .option("-h", "--help", "print help", { boolean: true });

// Slice off node executable and script from argument vector
const argv = process.argv.slice(2);

// And parse arguments. No exceptions to catch, instead check result object
const { ok, error, options } = synopt.parse(argv);

if (ok) {
  // Happy case
  main(options);
} else {
  // Handle errors: missing value, or unknown options/typos, etc.
  console.log(error);
  console.log(synopt.usage());
  process.exit(1);
}

synopt.usage() generates this usage banner.

Usage: mkwebmanifest [options]

Generate icons and web manifest for web applications

    -i,  --icon ICON           source icon file
    -n,  --name NAME           name of the web application
         --config FILE         configuration file
         --outdir <directory>  directory path for generated files
         --verbose             more output
    -h,  --help                print help

Synopt doesn't make assumptions about programs with subcommands (e.g. git branch), which often come with separate sets of options. But multiple sets of options are supported by createCommand(name) instead of importing the default synopt.

import { createCommand } from "synopt";

const init = createCommand("init")
  .option("--quiet", { boolean: true })
  .option("-h", "--help");

const store = createCommand("store")
  .option("-v", "--verbose", { boolean: true })
  .option("--name");

Command API

option([short], long, [description], [options])

Declares an option. Only the long form (--task NAME) is required, which consists of two dashes (--) and the option's name, optionally followed by the argument name to be shown in the usage banner (NAME). If the argument name is left off, the option name will be assumed (e.g. --task TASK).

The optional short form starts with a single dash (-), followed by a single letter. This form can appear as first or second positional parameter.

The optional description explains the meaning of the option, e.g. you can say if it's mandatory, or has certain legal values, or other contstraints.

The declaration options are passed as an object in last position of the arguments. boolean indicates an option which doesn't require a value (e.g. typical cases are --quiet or --dry-run).

option can be chained, because it returns the command itself.

summary(text)

This sets a summary text to be show on the usage banner. Returns the command itself for chaining.

description(text)

This sets a description to be show on the usage banner, below the summary. Returns the command itself for chaining.

name(text)

This sets a name to be show on the usage banner. Returns the command itself for chaining.

parse(argv)

Parse the arguments from the command line against the declared options and never throws an exception. Returns an result object of { ok, options, error }. Check ok for success of the parsing of the options, and display error to inform the user of problems.

The option object has this structure: string to string | boolean | string[]. The value is string, unless it's declared a boolean option, or a repeat option (string[]).

usage()

Return the usage banner as a string.

createCommand([name])

Create a command object, with an optional name. In many cases the name should be the executable, but sometimes an executable has subcommands with separate option interfaces each. You can create a command object for each subcommand.

If you use the convenience default import synopt from 'synopt;, this is a command without a name set yet.