1.0.0 • Public • Published

Curveball Problem Middleware

This package is a middleware for the Curveball framework that catches any exception and turns them into application/problem+json responses, as defined in RFC9457.

By default any exception turns into a non-descript 500 Internal Server Error. To create a more specific error, use an exception from the @curveball/http-errors package or implement one of the interfaces.


npm install @curveball/problem

Getting started

import problemMw from '@curveball/problem';
import { Application } from '@curveball/kernel';

const app = new Application();

Typically you will want the problem middleware to be one of the first middlewares you add to the server. Only exceptions from midddlewares that come after the problem middleware can be caught.

Throwing errors

You can throw the following kinds of errors.

  • Standard errors. These errors will be anonimized and logged to the console. a http 500 error gets emitted. (unless debug mode is on).
  • Errors with a httpStatus property. Any error that's thrown that has a httpStatus property will automatically use that http status. The error message will be used as a title.
  • An error from the http-errors package.

Debug mode

By default the middleware will emit a detailed error for any exception that implements the http-errors interfaces, because the assumption is that if these errors were emitted, they were intended for the user of the server.

Any exceptions that are thrown that don't implement these interfaces are stripped from their message and detail and converted to a 500 error to avoid potential security issues.

It's possible to turn this off during development in two ways. You can set the debug setting to true as such:

  debug: true

The second way is by setting the environemnt variable NODE_ENV to the string development.

If the debug property is set, that value always takes precedent.

Quiet mode

If quiet mode is enabled, 4XX errors are not logged. Client errors are common and usually expected behavior, so it might be preferable for them to not spam the log.

  quiet: true

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npm i @curveball/problem

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