ts-strict-error

ts-strict-error is an extremely simple little library that provides some nice ergonomics for creating errors in Typescript that you can ts-pattern against.

Motivation

Typescript's built-in Error class is very simple and extremely hard to handle. Most libraries don't add the required context to find out what's happening easily, if at all. Many libraries don't document the errors they throw either. This library provides a simple way to create complex errors, with typed context and causes. Together with ts-pattern, it somewhat mirrors the ergonomics of Rust's thiserror and match statements.

Also check out my blog post.

This repository also contains some converters to convert between Error and StrictError types, so you can use this library in combination with other libraries that throw Errors. There's an open discussion about those here.

Installation

This library is available on NPM and needs to be installed and packaged with your code:

# with npm
npm i -S ts-strict-error

# or yarn
yarn add ts-strict-error

Usage

import { createStrictError } from "ts-strict-error";

const NetworkError = createStrictError("NetworkError");
const NonOkStatusCode = createStrictError<
  "NonOkStatusCode",
  undefined,
  { code: number }
>("NonOkStatusCode");

const FetchError = createStrictError<
  "Fetch",
  InstanceType<typeof NetworkError> | InstanceType<typeof NonOkStatusCode>
>("Fetch");

match(new FetchErr({ from: new NonOkStatusCode({ context: { code: 500 } }) }))
  .with({ name: "Fetch", cause: { name: "NetworkError" } }, () => {
    console.log("No network connection available");
  })
  .with({ name: "Fetch", cause: { name: "NonOkStatusCode" } }, ({ cause }) => {
    console.log(`Received non-OK status code: ${cause.context.code}`);
  })
  .exhaustive();