Bug#1125161: Re-bootstrapping sbt and modern Scala; the Scala 3 path is now open

[Juan M. Méndez Rey]

Hi David,

Thanks for coming into discussion specially if it helps on 
simplifying the process! I had a look to the VirtusLab approach. 
  
So, please,let me see if what I gathered clarifies, then a question, 
because I think that option is not fully possible for 
the Debian approach.
  
1. The 3.9 library: noted, thanks. I'd been assuming "Scala 3 = the 2.13 stdlib", 
which holds to 3.8 but not 3.9's own _3 library. 
It only affects the future Scala 3 layer; but for 2.12/2.13 and its ecosystem are unchanged.

2. On "sbt + scala-cli bring the libraries": 

As far as I can see that works because they fetch deps from Maven Central via Coursier
(https://scala-cli.virtuslab.org/docs/guides/introduction/dependencies/). 

The Debian archive build targets must not attempt network access, so I believe this path
is not possible. 
  
If we were to package sbt/scala-cli that still needs every library packaged
from source under /usr/share/maven-repo; that download model 
is exactly what would prevent VirtusLab's .debs out of the archive, 
hence why I suggested the approach proposed in this thread.

Question: can you confirm the VirtusLab .debs work that way. Like, they rely on Coursier 
pulling dependencies at first use, rather than shipping them from the archive?

Just want to be sure I'm describing them accurately.
  
Best,
Juan