In a previous blog post, I started to play with org-babel-clojure to improve its capabilities such that Clojure gets better integrated into Org-mode for creating notebooks and Literate programs. The first thing I wanted to do is to remove the 20 seconds timeout that was defaulted with the nrepl. That meant that it was not possible to run procedures for longer than 20 seconds before it died with a timeout. Once this was implemented, the next step was to add a new feature to see the underlying process of a code block. Because the nature of my work (extensive work with big datasets), my procedures take time to run (minutes… hours…) and much information [about the process] is output to the terminal. However, in the org-babel-clojure implementation, you had to wait until the code was executed before being able to see the processing. What I did at the time is to add a new :async code block parameter which told org-babel-clojure to output all the output of the nrepl, when it was being processed, in a new window.
That worked like a charm. However, after much interaction with Nicolas Goaziou, one of the core maintainers of Org-mode, it was clear that my implementation was not an asynchronous implementation but really just a live processing output.
At the same time, I did find another major irritant: if an exception was raised in my Clojure code, then nothing was output to Org-mode, it was simply silently dying. The only way to see the exception was to switch to the Clojure major mode (using C-c ') and to rerun the code block.