npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

lambda-options

v0.0.7

Published

Typesafe declarative argument parser using pattern matching.

Downloads

6

Readme

About

  • lambda-options is a declarative argument parser:
    • Use callbacks with typed arguments to dictate parsing.
  • lambda-options is strongly typed:
    • Misuse of callbacks leads to compiler errors:
  • lambda-options is extensible:
    • You can add your own typed parsers.

Why

Typescript was lacking a good CLI argument parser. All the parsers I found were either weakly typed (usually from a vanilla JS project), didn't allow custom parsers, or proved difficult to use.

lambda-options was designed to solve all these problems.


How

With lambda-options, you register fully-typed parse callbacks for pattern matching keywords and their arguments.

Example:

import { Options } from "lambda-options";

const options = Options.createDefault();

// Matches ["--take", "5", "helloworld"]
options.addOption(
    "--take",           // Name of the keyword
    ["unsigned", "N"],  // [Type of 1st keyword argument, Argument help description name]
    ["string", "STR"],  // [Type of 2nd keyword argument, Argument help description name]
    "Takes the first N characters of STR.", // Help description
    (n: number,         // First argument. Strongly typed from "unsigned"
     s: string)         // Second argument. Strongly typed from "string"
     => {
        // Parse match action
        console.log(s.substr(0, n));
    }
);

The options structure that the option is registered to understands the types involved and will pattern match accordingly. For example, the above snippet will not match ["--take", "-1", "helloworld"].

Also note that if the callback had a different type for n: number, you will get a compiler error. Likewise for the s: string type.

A comprehensive list of built-in type parsers are listed later in this document.

If the built-in parsers are not sufficient for your needs, you can register your own parsers. These too are typesafe.


Quickstart Example

import { Options, Exception } from "lambda-options";

const options = Options.createDefault();

options.addOption(
    ["--help", "-h"],
    "Display this help message.",
    () => {
        console.log(options.getHelpDescription());
    }
);
options.addOption(
    "--take",
    ["unsigned", "NUM"],
    ["string", "STR"],
    "Takes the first NUM characters of STR.",
    (n: number, s: string) => {
        console.log(s.substr(0, n));
    }
);
options.addOption(
    "--sum",
    ["number", "NUM"],
    ["number[]", "NUMS"],
    "Takes the sum of 1 or more numbers.",
    (x: number, xs: number[]) => {
        console.log(xs.reduce((y, z) => y + z, x));
    }
);

declare const process: { argv: string[] };
const args = process.argv.slice(2);

const parseContext = options.createParseContext(args);

try {
    parseContext.run();
}
catch (e) {
    if (e instanceof Exception) {
        console.log(e.message);
        console.log(options.getHelpDescription());
    }
    else {
        console.log(e);
    }
}

Registering custom type parsers.

With Options.prototype.registerParser(typeName, parser) you can make lambda-options aware of your own custom types.

Example A:

import { Options, NoParse, parseNumber } from "lambda-options";

type Point = { x: number, y: number };

function pointParser(
    startIndex: number,
    args: string[])
    : [Point | NoParse, number]
{
    const [result1, consumed1] = parseNumber(startIndex, args);
    if (result1 === NoParse) {
        return [NoParse, consumed1];
    }
    startIndex += consumed1;

    const [result2, consumed2] = parseNumber(startIndex, args);
    if (result2 === NoParse) {
        return [NoParse, consumed1 + cosumed2];
    }

    const point = { x: result1, y: result2 };
    return [point, consumed1 + cosumed2];
}

const options = Options.createDefault()
    .registerParser("Point", pointParser);

There are serveral helper functions available too.

Example B:

import {
    Options,
    NoParse,
    parseNumber,
    createFixedArrayParser,
} from "lambda-options";

type Point = { x: number, y: number };

const parseNumber2 = createFixedArrayParser("2", parseNumber);

function pointParser(
    startIndex: number,
    args: string[])
    : [Point | NoParse, number]
{
    const [result, consumed] = parseNumber2(startIndex, args);
    if (result === NoParse) {
        return [NoParse, consumed];
    }
    const point = { x: result[0], y: result[1] };
    return [point, consumed];
}

const options = Options.createDefault()
    .registerParser("Point", pointParser);

You can use Options.prototype.registerParsers to easily get T? and T[] semantics as well.

Example C:

import {
    Options,
    NoParse,
    parseNumber,
    createFixedArrayParser,
} from "lambda-options";

type Point = { x: number, y: number };

const parseNumber2 = createFixedArrayParser("2", parseNumber);

function pointParser(
    startIndex: number,
    args: string[])
    : [Point | NoParse, number]
{
    const [result, consumed] = parseNumber2(startIndex, args);
    if (result === NoParse) {
        return [NoParse, consumed];
    }
    const point = { x: result[0], y: result[1] };
    return [point, consumed];
}

const options = Options.createDefault()
    .registerParsers("Point", "Point?", "Point[]", pointParser);

Built-in parse types

  • "boolean"boolean
  • "boolean?"boolean | undefined
  • "boolean[]"boolean[]
  • "string"string
  • "string?"string | undefined
  • "string[]"string[]
  • "number"number
  • "number?"number | undefined
  • "number[]"number[]
  • "integer"number
  • "integer?"number | undefined
  • "integer[]"number[]
  • "unsigned"number
  • "unsigned?"number | undefined
  • "unsigned[]"number[]
  • "Int8"number
  • "Int8?"number | undefined
  • "Int8[]"number[]
  • "Int16"number
  • "Int16?"number | undefined
  • "Int16[]"number[]
  • "Int32"number
  • "Int32?"number | undefined
  • "Int32[]"number[]
  • "Uint8"number
  • "Uint8?"number | undefined
  • "Uint8[]"number[]
  • "Uint16"number
  • "Uint16?"number | undefined
  • "Uint16[]"number[]
  • "Uint32"number
  • "Uint32?"number | undefined
  • "Uint32[]"number[]
  • "Int8Array"Int8Array
  • "Int16Array"Int16Array
  • "Int32Array"Int32Array
  • "Uint8Array"Uint8Array
  • "Uint16Array"Uint16Array
  • "Uint32Array"Uint32Array