Mechanism to catch and open exceptions from other threads in *cider-error* popup

[JosephFerano]

Is your feature request related to a problem? Please describe.

The cider error buffer is a great way to make Clojure's exceptions more ergonomic to read. However, if they are thrown from a different thread, such as when fiddling with UI in a JavaFx thread, then Cider is unable to catch them such that they raise the popup error buffer.

Describe the solution you'd like

Some sort of mechanism by which I can hook exceptions in other threads to trigger the cider error buffer popup.

Describe alternatives you've considered

Currently, I got it working, here's what i did;

First I used a workaround suggested in the slack;

(defonce last-exception (atom nil))

Then I assign a handler to Thread/setDefaultUncaughtExceptionHandler. Something along the lines of;

 (when (System/getProperty "cider-dev")
   (reset! last-exception exception)
   (log/error :message "EMACS-CIDER-REPORT-EXCEPTION"))

Then on the emacs side;

(defun joe/clojure-cider-throw-last-error ()
  (interactive)
  (cider-interactive-eval "\(throw @last-exception\)"))

(defun joe/cider-repl-preoutput-hook (output)
  (if (string-match "EMACS-CIDER-REPORT-EXCEPTION" output)
      (progn
        (joe/clojure-cider-throw-last-error)
        "")
    output))

(add-hook 'cider-repl-preoutput-hook #'joe/cider-repl-preoutput-hook)

The key being cider-repl-preoutput-hook