io-ts-docopt

Decode docopt output with io-ts

Docopt is a fantastic argument-parsing tool, but suffers from a few drawbacks:

1. The returned object has awkward keys like <name> that cannot be accessed with the dot accessor
2. Arguments (except flags) are always parsed as strings

This project combines docopt with io-ts to overcome both inconveniences, by first parsing arguments with docopt, then decoding and then encoding the parsed value through the specified io-ts codec. This sequence provides the opportunity to remap gnarly keys into more convenient identifiers, as well as decode values from one type into another (for example, with the NumberFromString codec).

Install

npm install io-ts-docopt

Use

import { decodeDocopt, withEncode } from 'io-ts-docopt'
 
const docstring = `
Usage:
    foo --clean <one> <two> <many>...
`
 
const codec = withEncode(
    iots.type({
        '--clean': iots.boolean,
        '<one>': iots.string,
        '<two>': iots.string,
        '<many>': iots.array(iots.string)
    }),
    (a) => ({
        clean: a['--clean'],
        one: a['<one>'],
        two: a['<two>'],
        many: a['<many>']
    })
)
 
decodeDocopt(
    codec,
    docstring,
    {argv: `--clean red blue green purple yellow`.split(/\s+/)}
)
//=> {
//       clean: true,
//       one: "red",
//       two: "blue",
//       many: ["green", "purple", "yellow"]
//  }

Documentation

See generated documentation.

Acknowledgments

• io-ts
• docopt