Creating errors from validation results

[dmitrizagidulin]

A typical usage for json-document validation is something like in jose/JWKSet.importKeys():

if (!validation.valid) {
  return Promise.reject(validation)
}

However, Promise.reject(), just like a regular throw, is supposed to accept Error objects. For various historical reasons, throw also accepts non-error objects (so you can throw a string, ie throw 'Something'). Same with Promise.reject(). However, this is considered an anti-pattern, and Standard linters flag this as an error.

Now, a validation result is currently not an Error instance, it's its own object.

So the question before us is this: What's the best way to turn a validation result into an Error instance? I'm currently doing something like:

return Promise.reject(new Error(JSON.stringify(validation)))

but that feels hack-y. We should actually consider a .error getter method on our validation result instances. (That would return a nice error instance, populated with a stringified validation error message.) So that the use can do:

return Promise.reject(validation.error)