disappearing argument parser

This is admittedly a little 🔬 mad science. The gist is that zeroarg is an argument parser, with yargs at its core, that doesn't require you to touch yargs, or argument-parsing specifics. It aims to infer types and reuse documentation to do that.

Here's an example CLI written with zeroarg:

var zeroarg = require('zeroarg');

zeroarg(() =>
  /**
   * Add numbers together
   * @param {Array<number>} numbers
   */
  function add(numbers) {
    console.log(numbers.reduce((sum, num) => sum + num, 0));
  }
);

This produces proper help material:

Commands:
  run [numbers..]

Options:
  --help  Show help     [boolean]

Add numbers together

And adds numbers together when you run it:

$ ./examples/add.js run 1 2 3 4
10

• Argument parsing still feels like a source of uncertainty in programming: it's like the same as parsing query arguments, except for the CLI: you're getting who knows what from who knows who. Your program has types and expectations - maybe even official types with Flowtype - and yet argument parsers make you redeclare those types, or even allow untyped, unexpected input. What if argument parsers leveraged your program's existing assumptions and treated CLIs more like functions?
• It's possibly a little less code to write, and one less API to learn! zeroarg's API surface is one function, and it uses existing standards (JSDoc & Flow) to express assumptions about argument types.
• It's super fun and weird.

zeroarg a code-free argument parser

Functions that you provide to zeroarg follow certain rules:

Their arguments work like:

[positionalArgument],
[positionalArgument2],
[variadicPositionalArgument],
[optionsArgument]

• The first arguments can be positional arguments.
• The last argument to the method can be an object that receives the flag arguments (like --option). Only the last argument can be an options object.
  • Options can have JSDoc types of string, number, array, and boolean.
  • If you specify a default in JSDoc-land, it becomes a default in yargs
  • If you specify an argument as an enum in JSDoc-land, it becomes choices in yargs

Parameters

• fn Function a function that returns a function, and has at least one JSDoc comment preceding that function.

Examples

zeroarg(() =>
 /**
  * Hello world
  *\/
 function helloworld() {
   console.log('Hello world');
 }
);