[Seaside-dev] Debugging in Seaside 3.0 (issue 340)

[Michael Lucas-Smith]

Hi All,

I'd like to kick off a (hopefully) short discussion on the direction of 
walkbacks and debugging with Seaside 3.0.

There is an open issue for debugging and walkbacks, issue 340 ( 
http://code.google.com/p/seaside/issues/detail?id=340 ) which points out 
that the new way exception handling works and continuations work 
basically means showing a walkback, let alone debugging, is pretty much 
impossible in the way it was done in Seaside 2.8.

You cannot render during an action, so any walkback during an action 
cannot be reported to the user without great difficulty. You can render 
during the render phase, but this often leads to a mess.

Julian and I had a chat at ESUG about a potential solution to debugging 
and walkbacks in Seaside 3.0. Specifically the debugging - instead of 
trying to provide a debugging solution in the web browser, we let the 
development environment handle it as per normal. This means you'll get a 
debugger pop up in the GUI. It means that in production, instead of a 
walkback, users get an Internal Server Error of some kind.

So how do we debug then? We have a separate Seaside request showing a 
list of debuggable processes, which you can refresh (and probably should 
refresh itself either via comet or polling) which you can click on to 
see a walkback, terminate, debug, etc.

The question was posed: could this be done and could it be portable?

Tamara Kogan has twisted the WebVelocity web debugger about until it is 
demonstrable, so here is the video:
http://dl.getdropbox.com/u/20291/Cincom%20Smalltalk/Seaside-20090918-Debugging.mov

The bad news: Every Smalltalk I looked at handles how the debugger is 
opened and how you debug a process completely differently. So while the 
technique is something that can be shared around the smalltalks, the 
code itself pretty much can't be.

Recommendations:
    1) An official "technique" could be published somewhere, on the 
seaside wiki perhaps, on how to implement debugging in Seaside for each 
implementation.
    2) The WAExceptionHandler* classes can be removed to dissuade people 
from expecting a way to do this reasonably.

What do people think about this?

Cheers,
Michael