Request for proposals on Rust and Go build systems (RE: Medium-term road map)

[John Soo]

Hi Guix,

I lost the specific thread on the medium-term road map that applies.  A
few suggestions have been made to improve updates the source-only build
systems we have (Rust and Go). I would like to suggest that we do make
changes to these and put them on the road map.

Can we put together some complaints and proposals for the rust and go
build systems? It would be nice to first get some informal ideas and
then see if we can't mostly agree on a final set of items to work on.

I have the following issues:

* The loop-breaking procedure is widely applicable: most other
  transitive dependencies should have loops in their dependency graphs
  broken. So far, only the cargo-build-system has such a loop-breaking
  procedure.

* It will be hard to track down breaking changes when a source-only
  library package is updated.  guix refresh --list-dependents usually
  shows how many packages would be effected by changing a package.  Rust
  packages, at least, do not show any dependent packages for libraries.

In the past, I have seen other complaints:

* Outputs from the cargo-build-system don't use dynamic linking.

* Namespacing of cargo packages is not good.

My suggestions:

* Move the dependency loop-breaking procedure from the rust build system
  to a utils location.  Use the procedure in more (if not most other)
  build system's transitive dependency resolution.

* Figure out a mechanism whereby source-only packages are registered by
  guix refresh --list-dependents. I had suggested moving
  #:cargo-dependencies to inputs, for instance.

I hope to hear from you soon!

- John