scala-cli-repl: a Scala REPL based on scala-cli
Too long; didn't read
I have been reading books about Scala libraries lately and it was fun to see how the transition to Scala 3 is in progress. Since code examples use both Scala 2 and 3, I have struggled testing things out in an easy way. I was following along with Ammonite, which allowed me to try libraries easily in scripts, and then I discovered scala-cli which also allowed me to switch between Scala versions easily.
Since I like to take notes in Org Mode, I thought it would be cool to have a REPL and org babel extension for Emacs running on scala-cli. Apparently nobody felt the need to make a mode yet, so how could I not be the first?
And there is a solution
So far I had been using ammonite-term-repl, a mode for Ammonite and that has been archived recently. After a bit of tweaking I found out that by changing some variables the mode worked fine also for scala-cli. Since it was archived, I cleaned it up a little bit and made a new repository that focuses on scala-cli: scala-cli-repl.
This is how the REPL look:
I added also a function to convert SBT dependencies into the Mill
format that scala-cli accepts (
should make it easier to try things out.
The interesting bit has been to support org babel for Scala. This relies on the REPL. For my needs I wanted to support setting a Scala version and dependencies as header arguments of a source block.
The extension supports blocks like these:
#+begin_src scala :dep '("com.lihaoyi::os-lib:0.9.0" "com.lihaoyi::utest:0.7.10") println("This is:" + os.pwd) #+end_src
Given I like to try things in Org Mode source blocks, I thought that would have been cool to get some code completions that scala-metals usually provide me.
This is how it looks to setup a scala block with my
You can see that I was able to complete
os.pwd using scala-metals
from an Org Mode block!
The implementation uses lsp-org (which is part of lsp-mode) and scala scripts (file ending with .sc). All in all, is pretty cool to work on Scala examples with full IDE support in your literate programming! And now I can more easily follow my books along :)