Re: I'm enhancing GWT to provide Java stack traces for clientside exceptions in production

What GWT needs here is something closer to what you get with proguard - a mapping file created during compilation that could be used to run the obfuscated/javascript exception through a utility to give the correct stack trace with zero overheads.

I'm not entirely sure on how proguard accomplishes it, but I'd say it would be the perfect solution.

We also do not use emulated stack traces because of performance and code size overhead. So we simply deploy the symbol maps generated by GWT compiler and use StackTraceDeobfuscator on the server. We also extended StackTraceDeobfuscator a bit because we received exceptions where the stack trace is actually inside the exception message instead of the exception stack trace (the exception stack trace was empty). So we try to deobfuscate the exception message as well in this case.

Given the above the quality of stack traces now depends on the browser version our clients use. We do not support IE6/7 and IE 8 support will be dropped next year (regardless of what GWT does). So we mainly deal with newer browsers and we pretty much always get deobfuscated stack traces that provide some useful information. Its not perfect but it works. We never get the concrete line number where the exception occurs but we often enough have the method name. Of course sometimes we have no stack information at all (IE8).

In addition you can enhance the stack trace by providing additional client information. For example you could send the current URL to the server which tells your the current place state if you use GWT Places. You could also implement a custom Logging Handler that logs into a ring buffer and once a client exception occurs you send the last x client log entries along with the stack trace. Or if you do not want to enable logging itself in production you could still use the ring buffer approach and store "user actions" in it and then send these to the server (similar to client side logging). Or you trace user click coordinates and their underlying elements (event preview handler)

So before enabling full stack trace emulation in GWT you can do quite a few things to get information about what has happened inside the app once the exception had occurred. 

Btw. we stopped using SourceMaps for Chrome because for whatever reasons StackTraceDeobfuscator has imports from gwt-dev.jar that are needed when SourceMaps are enabled.

-- J.

 

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