Wrapping an R script: how do I compose the R_LIBS_SITE environment variable?

[divoplade <d@divoplade.fr>]

Dear guix,

I am using guix to write R packages. For convenience, I created a small
R script that does the job.

To make this script work as-is, I wrapped it using wrap-program. wrap-
program creates a shell script that sets up environment variables and
then call the real script, because R needs to be able to find all the
packages and dependencies. More specifically, I need to extend the
R_LIBS_SITE environment variable to point to all the R dependencies of
my package, as well as their recursive dependencies.

How do I compute that? I only care about R dependencies, so using the
whole recursive dependency tree of my package seems too much.

My current solution is to save the R_LIBS_SITE environment from the
build procedure and just use that. The obvious problem is that it also
contains build dependencies, and I don't think it will work correctly
for cross-compiled packages.

Do you have a better idea?

Best regards,

divoplade