Make it simpler in `ExecutionDiagnosticEventListener.ResolverError` to distinguish between server and client errors

Product

Hot Chocolate

Is your feature request related to a problem?

I want to log all server errors as errors, and all client errors at a lower severity level. However, ExecutionDiagnosticEventListener.ResolverError gives me no robust way to distinguish between them.

I originally tried to base this on whether the IError passed to ResolverError contains an exception, but this does then not log errors like HC0018 "Cannot return null for non-nullable field" as errors. I can of course add this code to the check, but adding error codes as I randomly discover that something is not logged as an error is no way to go about this.

The solution you'd like

I'm open to various solutions, but it could be something as simple as a property IError.IsServerError or IError.IsClientError.

Start by reviewing ExecutionDiagnosticEventListener.ResolverError and the IError passed to it, including the HC0018 example. Determine how server and client errors should be distinguished reliably, then define the API behavior and verify that both exception-backed errors and errors such as non-nullability failures are classified correctly.