Exceptions and other output from gui thread end up in another buffer when using an Emacs/CIDER REPL

[m-r-hunt]

I'm not sure if this is the correct forum for this post but I want to share this on the off chance someone else has this problem and I can save them an hour's worth of frustration.

TL;DR If you're using Emacs and CIDER REPL with seesaw, exception messages and other output from the swing gui/event thread end up in the buffer named nrepl-server .

After a frustrating debugging session I finally discovered why my custom painting function wasn't working: I had missed an argument to a function and it was throwing an exception. I couldn't see this, or any other output from, for example, println, when running from a REPL. I finally figured out what was going on by running my project from the command line where I got an epic stack trace every time paint was called. After more poking about I finally found out that the output from the swing event thread ends up in another buffer, not in the REPL buffer. I then felt like an idiot.

[daveray]

It seems like this could be helped with some emacs-specific notes in the documentation, but otherwise, it seems like a cider-specific issue that would affect any code that's printing or logging exceptions in a separate thread. Sorry to hear you had trouble with this.