[Cc Ricardo since you wrote the texlive importer]

In section "9.5 Invoking ‘guix import’" in the manual, there are two
examples of runnning the ‘texlive’ importer, but both of them result in
incomplete package definitions.

--8<---------------cut here---------------start------------->8---
~/src/guix$ ./pre-inst-env guix import texlive fontspec
following redirection to `https://ctan.org/xml/1.2/pkg/fontspec'...
command "svn" "export" "--non-interactive" "--trust-server-cert" "-r" "51265" "svn://www.tug.org/texlive/tags/texlive-2019.3/Master/texmf-dist/source/latex/fontspec" "/tmp/guix-directory.O5HIN3/svn" failed with signal 11
guix import: warning: Could not determine source location.  Please manually specify the source field.
(package
  (name "texlive-latex-fontspec")
  (version "2.7i")
  (source #f)
  (build-system texlive-build-system)
  (arguments '(#:tex-directory "latex/fontspec"))
  (home-page "http://www.ctan.org/pkg/fontspec")
  (synopsis
    "Advanced font selection in XeLaTeX and LuaLaTeX")
  (description
    "Fontspec is a package for XeLaTeX and LuaLaTeX.  It provides an automatic and unified interface to feature-rich AAT and OpenType fonts through the NFSS in LaTeX running on xetexXeTeX or luatexLuaTeX engines.  The package requires the l3kernell3kernel and xparsexparse bundles from the LaTeX3 development team.")
  (license lppl1.3c))
--8<---------------cut here---------------end--------------->8---

--8<---------------cut here---------------start------------->8---
~/src/guix$ ./pre-inst-env guix import texlive --archive=generic ifxetex
following redirection to `https://ctan.org/xml/1.2/pkg/ifxetex'...
command "svn" "export" "--non-interactive" "--trust-server-cert" "-r" "51265" "svn://www.tug.org/texlive/tags/texlive-2019.3/Master/texmf-dist/source/generic/ifxetex" "/tmp/guix-directory.GjfISH/svn" failed with signal 11
guix import: warning: Could not determine source location.  Please manually specify the source field.
(package
  (name "texlive-generic-ifxetex")
  (version "0.7")
  (source #f)
  (build-system texlive-build-system)
  (arguments '(#:tex-directory "generic/ifxetex"))
  (home-page "http://www.ctan.org/pkg/ifxetex")
  (synopsis "Am I running under XeTeX?")
  (description
    "A simple package which provides an \\ifxetex conditional, so that other code can determine that it is running under XeTeX.  The package requires the etexe-TeX extensions to the TeX primitive set.  Please note, that ifxetex is now part of iftexiftex.")
  (license lppl1.3c))
--8<---------------cut here---------------end--------------->8---

When looking at the CTAN page for ‘ifxetex’[1], it says that the source
in located in /macros/generic/iftex, but I tried a few paths for the
archive, and they all result in an incomplete package (same warning as
above).

* /macros/generic/iftex
* macros/generic/iftex
* /macros/generic/iftex/ifxetex
* macros/generic/iftex/ifxetex

In general, I have rarely been able to successfully import a CTAN
package using the texlive importer, without the ‘source’ field missing,
perhaps it needs an update?