Errorgant

try catch can get messy quickly, Errorgant is a simple, type-safe way to handle errors inline elegantly.

Features

• 🎯 Type-safe error handling
• 🔍 Discriminated error types with custom keys
• 📦 Optionally include context data with type infer-ed
• 🛡️ Run any throwable function and handle errors inline

Briefly

• errorgant is simpler to create then Error class and it support discriminate key, inferred context
• errorgantly run with an arrow function, it catches the error and return an Errorgant object with the error attached to ctx for you to handle it inline.
• isErrorgant is a powerful type guard, it not only narrowing down a variable to Errorgant type, but also can "filter" Errorgant by discriminate key so you handle a specific error once at a time.
• (Experimental) errorgantify, turns a throwable function not throw, returning an Errorgant object with the error attached to ctx. And "it knows generic function", function being errorgantify won't lose its generic behavior.

Installation

npm install errorgant
# or
yarn add errorgant
# or
pnpm add errorgant

Guide

try catch vs Errorgant

With try catch, you can only handle errors in one place. And can quickly lose track of what error is thrown where.

function mightHaveError() {
  /* ... */
  throw new Error('ERROR_A');
  /* ... */
  throw new Error('ERROR_B');
  /* ... */
  return 'success';
}

try {
  const value = mightThrow();
  /* continue with the value */
} catch (e) {
  /* handle all errors here */
}

Instead of throws an error, return an Errorgant object to represent the error. Even better, pass a key to errorgant so you can handle a specific error one at a time discriminately.

function mightHaveError() {
  /* ... */
  return errorgant('ERROR_A');
  /* ... */
  return errorgant('ERROR_B');
  /* ... */
}

const value = mightHaveError();

if (isErrorgant(value)) {
  /* handle all errors in one shot */
} else {
  /* continue with the value */
}

if (isErrorgant(value, 'ERROR_A')) {
  /* handle only ERROR_A */
} else if (isErrorgant(value, 'ERROR_B')) {
  /* handle ERROR_B */
} else {
  /* continue with the value */
}

Need more context about the error? errorgant get you a inferred context

const mightBeAnErrorgant = errorgant('NO_AUTH', {
  msg: 'User should be authenticated',
});
mightBeAnErrorgant.ctx;
//                 ^?
//                 (property) ctx: {
//                   readonly msg: "User should be authenticated";
//                 }

Just want to catch an error inline without writing a wrapper function yourself?

errorgantly runs a function and returns an Errorgant, with the error attached in ctx property, if the function throws.

function mightThrow() {
  if (Math.random() > 0.5) {
    throw new Error('ERROR_A');
  }
  return 'success';
}

const value = errorgantly(mightThrow);

if (isErrorgant(value)) {
  const theError = value.ctx;
  //    ^? unknown
} else {
  /* continue with the value */
}

(Experimental) errorgantify can turn any throwable function not throw, returning an Errorgant object instead

function mightThrow() {
  if (Math.random() > 0.5) {
    throw new Error('ERROR_A');
  }
  return 'success';
}

const wrapped = errorgantify(mightThrow);

const value = wrapped();

if (isErrorgant(value)) {
  const theError = value.ctx;
} else {
  /* continue with the value */
}

TODO

• A TypeScript playground to experience with the library
• Let user type the context of Errorgant returned by errorgantly
• A function returning any make errorgantly, errorgantify not type-safe
• errorgantify might not transform a generic function correctly, though I don't have an example currently