Lightsail javascript SDK exception type checking with instanceof operator within typescript

[mikey-t]

I'm having an issue trying to catch an exception from the Lightsail SDK (v3) using instanceof in my typescript CLI app I'm running with NodeJS via ts-node. I decided to post a discussion question instead of an issue because I'm guessing there's a good chance I just don't know something about typescript or I misunderstood the docs in some way.

Here are my versions:

• typescript 5.1.6
• ts-node 10.9.1
• @aws-sdk/client-lightsail 3.363.0

Issue: sending a GetInstanceCommand or GetStaticIpCommand for a resource I know doesn't exist doesn't return a NotFoundException like I expect (err instance NotFoundException). The only exception I'm able to detect using instanceof is LightsailServiceException (the exception base class). I would like to be able to detect the NotFoundException using instanceof and the specific exception type instead of comparing the error's "name" property to the string "DoesNotExist" (which isn't in the docs at all - had to just look at some errors to see what to look for) or only ever looking for LightsailException and just assuming it's because it wasn't found.

Docs:

• The GetInstanceCommand docs for my version: https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/client/lightsail/command/GetInstanceCommand/
• The AWS blog post I read which outlines how errors were handled by callers in previous versions of the javascript SDK, and new examples for v3 using instanceof ExceptionType: https://aws.amazon.com/blogs/developer/service-error-handling-modular-aws-sdk-js/

Based on the exception detail, it sort of looks like it could actually "be a NotFoundException" (based on the __type property), but that typescript (or something I've done wonky) just can't differentiate between the instance and it's base class:

DoesNotExist: The Instance does not exist: non-existent-1
{
  '$fault': 'client',
  '$metadata': {
    httpStatusCode: 400,
    requestId: '94b2f9ab-8664-4311-969a-61e06bb123f3',
    extendedRequestId: undefined,
    cfId: undefined,
    attempts: 1,
    totalRetryDelay: 0
  },
  __type: 'NotFoundException',
  code: 'DoesNotExist'
}

Is there something obvious I'm missing or is it known/intended that you can't actually check the instance of the specific exception, but only the base exception type using instanceof?

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.