Error instance serialization missing properties

[john-goldsmith]

TL;DR: When deserializing an instance of Error, certain properties defined by the spec are dropped -- is this intentional and, if so, why?

---

The JSON:API spec states that error objects MAY have the following members:

id: a unique identifier for this particular occurrence of the problem.
links: a links object containing the following members:
    about: a link that leads to further details about this particular occurrence of the problem.
status: the HTTP status code applicable to this problem, expressed as a string value.
code: an application-specific error code, expressed as a string value.
title: a short, human-readable summary of the problem that SHOULD NOT change from occurrence to occurrence of the problem, except for purposes of localization.
detail: a human-readable explanation specific to this occurrence of the problem. Like title, this field’s value can be localized.
source: an object containing references to the source of the error, optionally including any of the following members:
    pointer: a JSON Pointer [RFC6901] to the associated entity in the request document [e.g. "/data" for a primary data object, or "/data/attributes/title" for a specific attribute].
    parameter: a string indicating which URI query parameter caused the error.
meta: a meta object containing non-standard meta-information about the error.

However, when serializing an instance of Error, the id, links, links.about, source, source.pointer, source.parameter, and meta members are not supported:

json-api-serializer/lib/JSONAPISerializer.js

Lines 411 to 419 in f99b2c0

	if (err instanceof Error) {
	const status = err.status || err.statusCode;
	serializedError = {
	status: status && status.toString(),
	code: err.code,
	title: err.title || err.constructor.name,
	detail: err.message,
	};

Current implementation:

const error = new Error('Something went wrong')
error.status = 500
error.code = 'abc123'
error.id = 'a745776d-08bc-486d-85ed-edc38dd120a0'
error.links = { about: 'https://examples.com' }
error.source = { pointer: '/data/attributes/title', parameter: 'include' }
error.meta = { time: Date.now() }
const serializedError = Serializer.serializeError(error)
/*
{
  errors: [
    {
      status: '500',
      code: 'abc123'
      title: 'Error'
      detail: 'Something went wrong'
    }
  ]
}
*/

If all of the JSON:API error object properties were supported, then custom errors could package up all of the related data and then be reused throughout an application while still maintaining Error class semantics. I realize that the serializeError function can also be passed an arbitrary object that gets validated, but this doesn't seem ideal.

Proposed usage:

// errors/my-custom-error.js
class MyCustomerError extends Error {
  constructor(message = 'Lorem ipsum dolor...') {
    super(message)
    this.status = 500
    this.code = 'abc123'
    this.title = 'MyCustomError'
    this.detail = message
    this.id = 'a745776d-08bc-486d-85ed-edc38dd120a0'
    this.links = { about: 'https://examples.com' }
    this.source = { pointer: '/data/attributes/title', parameter: 'include' }
    this.meta = { time: Date.now() }
  }
}

// somewhere/else.js
const serializedError = Serializer.serializeError(new MyCustomerError())

I'm happy to submit a PR if this is something you'd like to include. Thanks!

[danivek]

@john-goldsmith

Indeed, things are missing on the serialization of an instance of Error and it's not intentional.

Thanks for pointing this out. You can submit a PR!