Based on my experience, this also isn't true. I added support for Ruby gems in the GNU Guix package manager. The way it was done was by creating a Ruby-specif

Based on my experience, this also isn't true. I added support for Ruby gems in the GNU Guix package manager. The way it was done was by creating a Ruby-specific build system that Ruby-based software packages elect to use. We have a generic model that allows for many types of specific build systems to exist that deal with the domain-specific concerns. This generic models works better than a Ruby-specific model because, unlike RubyGems, Guix can capture the entire dependency graph. Take the Pg gem, for example. In order to build and use it, you need the libpq shared library. RubyGems can't encode this dependency, but Guix can. The recipe for ruby-pg is only 25 lines long: http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/ruby.scm#n2669 http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/... There was a talk given at FOSDEM about foreign packages in Guix with a focus on Ruby which is worth watching or skimming the slides: https://fosdem.org/2016/schedule/event/guixmodules/ https://fosdem.org/2016/schedule/event/guixmodules/