@tshttp/error v2.0.0

@tshttp/error 💢

The ultimate HTTP error to throw.Built with a simple and discoverable API surface, highly typed, with augmentation in mind.

Get started

Requires at least typescript 4.0.

yarn add @tshttp/error
npm install @tshttp/error

import { HttpError } from '@tshttp/error'

throw new HttpError(400)
throw new HttpError(500, 'My bad')

Attached properties

status

The resulting error has a status property that will be used, for example by Express and Fastify error handlers, to properly set the HTTP response status.

name

The resulting error name property will be inferred from status: e.g. "NotFound" for 404.

If you use a unknown error status code, the error name will be "HttpError".

Need more?

Have a look at the Augmentations section.

Enumerability

To respect the inherited Error, non-enumerable properties are kept non-enumerable: name, message, stack.They won't be serialized by JSON.stringify (MDN reference).

Dedicated static methods

Instead of passing the status code, the known HTTP errors are exposed as static methods: List of HTTP errors.

throw HttpError.Unauthorized('Get out')
// HttpError { status: 400, name: 'Unauthorized', message: 'Get out' }

throw HttpError.InternalServerError('My bad') 
// HttpError { status: 500, name: 'InternalServerError', message: 'My bad' }

Optional new keyword

You can instantiate HttpError with or without the new keyword, just like the built-in Error constructor.

throw HttpError(401)

The compiler is okay with both. 👌

Augmentations

By default, the only parameter you can pass besides the status code is message?: string. You might want your error objects to have more details.

A dedicated namespace Augmentation gives the possibility, for each different status, to change the optional message parameter to a required data object parameter. This object's properties will be attached to the resulting error (at runtime and compile time).

export {} // necessary to be in a module file

declare module '@tshttp/error' {
  namespace Augmentation {
    interface Forbidden {
      access: 'read' | 'create' | 'update' | 'delete'
      target: string
    }

    // Could be useful for custom headers since frameworks usually set the response headers with the error headers property:
    interface MethodNotAllowed {
      headers: {
        allow: ('GET' | 'POST' | 'PUT' | 'PATCH' | 'DELETE')[]
      }
    }
  }
}

throw HttpError(403, { access: 'read', target: 'user' })
// HttpError { status: 400, name: 'Forbidden', access: 'read', target: 'user' }

throw HttpError.MethodNotAllowed({ headers: { allow: ['GET'] } })
// HttpError { status: 505, name: 'MethodNotAllowed', headers: { allow: ['GET'] } }

Every known HTTP error is available for augmentation under its own name: List of HTTP errors.

If you want to augment every HTTP error at once, use the AnyHttpError interface.

Constraint

With the Constraint interface, you can:

• Whitelist the errors you application uses.

declare module '@tshttp/error' {
  namespace Augmentation {
    interface Constraint {
      status: 400 | 401 | 403 | 404 | 405 | 422 | 500
      // or widen to all numbers with `status: number`
    }
  }
}

• Force usage of static methods.

declare module '@tshttp/error' {
  namespace Augmentation {
    interface Constraint {
      constructor: false
    }
  }
}

HttpError(400) // Compile time error
HttpError.BadRequest() // Ok

message property stringification

If you define a message property with different type than string, like so:

declare module '@tshttp/error' {
  namespace Augmentation {
    interface AnyHttpError {
      message: Record<string, any>
    }
  }
}

it will always be stringified to respect the original Error interface (at runtime and compile time).

So:

throw HttpError(400, { message: { about: 'thing' } })

gives the following stack trace:

BadRequest: {"about":"thing"} # instead of "BadRequest: [Object object]"
    at ...

Protections

Since these augmentations affect the error object itself, you cannot define the following properties: name, status, stack, __proto__, constructor, prototype.

List of HTTP errors