Static error codes

[alchar]

It'd be great if JOSEError, and the errors that extend it, had static error codes.

For example:

export class JOSEAlgNotAllowed extends JOSEError {
  static code = 'ERR_JOSE_ALG_NOT_ALLOWED'
  code = 'ERR_JOSE_ALG_NOT_ALLOWED'
}

This is just to make it possible to get the code, without having to create a new instance of the class.

In our use case, we emit a metric with the error code on some failures. The unit tests look like:

assert(emittedMetric === new JWTExpired("test message").code);

which isn't nearly as clean as:

assert(emittedMetric === JWTExpired.code);

I imagine there are other cases where developers may find this a cleaner solution.

I'd be happy to submit this PR if it's something you'd like it. Either way, thanks for the great library!

[panva]

Sounds good. Would you give the PR a shot?

[alchar]

Will do!

[panva]

Altho the point of these error codes is that you just hard code their values.

You can just as well do instanceof checks otherwise.

[alchar]

We can definitely hardcode the values, I just found that to not be as clean as importing them directly from the library, especially if the string is used in multiple places.

instanceof checks work and are preferred when there's an object, but there isn't in this case.

If you're interested, I've opened the PR here.