How to catch unhandled exceptions thrown by custom language dll in Client App

Hi Rick,

I'm curious what kind of unhandled exceptions you'd plan on seeing?  In general, you should be able to design your lexer, parser, etc. language services with proper structured exception handling within the code itself so there never is an unhandled exception.  If you did encounter some scenario where something needed restarted (or switching to a lesser version of the syntax language), you could make a custom event sink service and call into that when the scenario occurs.  The event sink could possibly have a method that adjusts the registered services on the syntax language to unregister ones for your language server and register new ones needed for a .langdef-oriented setup.

Thanks.  My original thought was to let the client catch any error thrown by the language server since so I can log it and shut it down. But that's not going to work given that I can't mark the event handled and let the client continue running.  Using a custom event sink service to communicate back to the client is a good alternative.  Can you provide guidance/example on how to create a custom event sink service and call it? I can't find anything in the docs other than that it can be done.

Hi Rick,

Our event sinks get called through some internal methods.  The event sink concept is geared for public broadcast of some event.  If you only have one bit of logic that would ever occur in this scenario, it would be easiest to make a simple class instead of implementing the event sink concept.  Here's some quick steps to do that.

1) Make class MyLanguageErrorProcessor that has a method to call when the language error occurs.

2) Register that MyLanguageErrorProcessor as a language service on the ISyntaxLanguage using a call like language.RegisterService(new MyLanguageErrorProcessor()).

3) When your code detects a language error scenario, get the ISyntaxLanguage instance and call the language.GetService<MyLanguageErrorProcessor>() method to get the instance of your processor class.

4) Invoke your processor's method and do whatever logic you need within that.

I hope that helps.

Exactly what I needed and works perfectly.  Thank you!