nlf / minargs

minimal argument parsing - bring your own validation™️

minargs

minargs is an argument parser with minimal configuration & assumptions. Argument parsing can take many shapes but the explicit goals of this library are as follows:

Goals

• no usage
• no validation
• no types or type cohersion
• no regular expressions
• no strictness
• no dependencies
• no information loss
• minimal assumptions
• minimal configuration
• 100% test coverage

Mantras

• Bring Your Own Usage™️
• Bring Your Own Validation™️

Installation

npm install minargs

miargs([argv][, options])

• argv (Array)
  • Default: process.argv
  • The argument strings to parse

Options

• alias (Object)
  • Default: none
  • Define shorts & aliases to map to a canonical argument
  • Note: only single character aliases can be parsed as "shorts" (read more in the F.A.Q. below)
• positionalValues (Boolean)
  • Default: false
  • Define whether or not to use positionals that follow flags as values

Returned Values

{
  args: {},
  positionals: [],
  remainder: [],
  argv: []
}

args

• An Object of canonical argument keys with corresponding Array of parsed String values
• Examples:
  • --foo=bar will return ["bar"]
  • --foo bar will return ["bar"] when positionalValues is true
    • Notably, bar is treated as a positional & returned in positionals if positionalValues is false

positionals

• An Array of positional parsed positional String values

remainder

• An Array of String values the follow the first bare --
• Notably, this is useful for recursively parsing arguments or passing along args to other processes (read more in the F.A.Q. below)

Example Usage

Basic

$ basic.js - --foo=bar -- --baz

#!/usr/bin/env node

// basic.js
const { minargs } = require('minargs')
const { args, positionals, remainder, argv } = minargs()

args          // { "foo": ["bar"] }
positionals   // ["-"]
remainder     // ["--baz"]
argv          // [ { index: 0, type: 'argument', value: '{ ... }' }, ... ]

Handling existence

Toggle Example

$ exists.js --foo

#!/usr/bin/env node

// exists.js
const { minargs } = require('minargs')
const { args } = minargs()
if (args.foo) {
  // ...
}

Handling last value define

Toggle Example

$ last-definition-.js --foo

#!/usr/bin/env node

// exists.js
const { minargs } = require('minargs')
const { args } = minargs()
if (args.foo) {
  // ...
}

Handling unknown args

Toggle Example

$ unknown.js --baz

#!/usr/bin/env node

// unknown.js
const { minargs } = require('minargs')
const { args } = minargs()
const known = ['foo', 'bar']
const unknown = Object.keys(args).filter(arg => !known.includes(arg))
if (unknown.length > 0) {
  console.error('unknown flags passed:', unknown)
  // stop the process & set an `exitCode` appropriately
  process.exit(1)
}

// ...

Handling validation

Toggle Example

$ validate.js --num=1337

#!/usr/bin/env node

// validate.js
const { minargs } = require('minargs')
const { args } = minargs()
const usage = {
  num: {
    validate: (value) => {
      if (!isNaN(value)) {
        return Number(value)
      }
      throw Error('Validation error!')
    }
  },
  force: {
    validate: (value) => {
      if (~['true','false'].indexOf(value.toLowerCase())) {
        return Boolean(value)
      }
      throw Error('Validation error!')
    }
  }
}

Object.keys(args).filter(name => args[name]).map(name => {
  usage[name].validate(args[name].pop())
})

// ...

Handling recursive parsing

Toggle Example

$ recursive-parse.js

#!/usr/bin/env node

// recursive-parse.js
const { minargs } = require('minargs')

function minargsRecursiveSyncArray(argv, arr) {
  arr = arr || []
  const result = minargs(argv)
  arr.push(result)
  if (result.remainder.length > 0) {
    minargsRecursiveSyncArray(result.remainder, arr)
  }
  return arr
}

minargsRecursiveSyncArray(process.argv) // array of results

function minargsRecursiveSyncFlat(argv, obj) {
  const result = minargs(argv)
  obj = obj || { args: {}, positionals: [] }
  obj.args = { ...obj.args, ...result.args }
  obj.positionals = obj.positionals.concat(result.positionals)
  if (result.remainder.length > 0) {
    minargsRecursiveSyncFlat(result.remainder, obj)
  }
  return obj
}

minargsRecursiveSyncFlat(process.argv) // flattened results object

// ...

Handling sub process

Toggle Example

$ mkdir.js ./path/to/new/dir/ --force --verbose --parents

#!/usr/bin/env node

// mkdir.js
const known = ['force']
const { args, positionals } = minargs()
const cmd = (args.force) ? 'sudo mkdir' : 'mkdir'
const _args = Object.keys(flags).filter(f => known[f])

process('child_process').spawnSync(cmd, [..._args, ...positionals])

Handling robust options & usage

Toggle Example

$ usage.js -h

#!/usr/bin/env node

// usage.js
const { minargs } = require('minargs')
const usage = {
  help: {
    short: 'h',
    usage: 'cli --help',
    description: 'Print usage information'
  }
  force: {
    short: 'f',
    usage: 'cli --force',
    description: 'Run this cli tool with no restrictions'
  }
}
const opts = {
  alias: Object.keys(usage).filter(arg => usage[arg].short).reduce((o, k) => {
    o[usage[k].short] = k
    return o
  }, {})
}
const { args } = minargs(opts)

if (args.help) {
  Object.keys(usage).map(name => {
    let short = usage[name].short ? `-${usage[name].short}, ` : ''
    let row = [`  ${short}--${name}`, usage[name].usage, usage[name].description]
    console.log.apply(this, fill(columns, row))
  })
}

/// ...

F.A.Q.

Why isn't strictness supported?

• Strictness is a function of usage. By default, minargs does not assume anything about "known" or "unknown" arguments or their intended values. Usage examples above show how you can quickly & easily utilize minargs as the backbone for an application which does enforce strictness, validation & more.

Are shorts supported?

• Yes.
• -a & -aCdeFg are supported
• -a=b will capture & return "b" as a value
• -a b will capture & return "b" as a value if positionalValues is true

What is an alias?

• An alias can be any other string that maps to the canonical option; this includes single characters which will map shorts to a long-form (ex. alias: { f: foo } will parse -f as { args: { 'foo': true } })

Is cmd --foo=bar baz the same as cmd baz --foo=bar?

• Yes.

Is value validation or type cohersion supported?

• No.

Are usage errors supported?

• No.

Does --no-foo coerce to --foo=false?

• No.
• It would set { args: { 'no-foo': true } }

Is --foo the same as --foo=true?

• No.

Are environment variables supported?

• No.

Does -- signal the end of flags/options?

• Yes.
• Any arguments following a bare -- definition will be returned in remainder.

Is a value stored to represent the existence of --?

• No.
• The only way to determine if -- was present & there were arguments passed afterward is to check the value of remainder

Is - a positional?

• Yes.
• A bare - is treated as & returned in positionals

Is -bar the same as --bar?

• No.
• -bar will be parsed as short options, expanding to -b, -a, -r (ref. Utility Syntax Guidelines in POSIX.1-2017)

Is ---foo the same as --foo?

• No.
• ---foo returns { args: '-foo': true }
• --foo returns { args: { 'foo': true }

Is foo=bar a positional?

• Yes.

Are negative numbers supported as positional values?

• No.
• minargs aligns with the POSIX Argument Syntax here (ie. "Arguments are options if they begin with a hyphen delimiter")
• --number -2 will be parsed as { args: { 'number': true, '2': true } }
• You will have to use explicit value setting to make this association (ex. --number=-2) & may further require validation/type coercion to determine if the value is a Number (as is shown in the usage examples above)

CLI

minargs has a companion CLI library: @minargs/cli

Installation

# install package globally & call bin...
npm install minargs -g && minargs

# or, use `npx` to install & call bin...
npx minargs

Usage

minargs "<args>" [<options>]

Options & more....

To learn more, check out the @minargs/cli GitHub repository or package page