bug#48082: “guix environment -l” does not work with inferior packages

[Ricardo Wurmus <rekado@elephly.net>]

I wanted to use an environment file that contains a package 
definition, and use it with inferiors.  Here is the full guix.scm:

--8<---------------cut here---------------start------------->8---
(use-modules
 (guix channels)
 (guix inferior)
 (guix build-system gnu)
 (guix packages)
 (guix licenses)
 (gnu packages)
 (ice-9 match))

(define channels
  (list (channel
         (name 'guix-bimsb)
         (url "https://github.com/BIMSBbioinfo/guix-bimsb.git")
         (commit
          "be42b099867a29a68a9ffbf304dc7f9137b75fe3"))
        (channel
         (name 'guix)
         (url "https://git.savannah.gnu.org/git/guix.git")
         (commit
          "01e33a031e493477d930b9383d397fea012a3b1a")
         (introduction
          (make-channel-introduction
           "9edb3f66fd807b096b48283debdcddccfea34bad"
           (openpgp-fingerprint
            "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 
            54FA"))))))

(define (lookup name)
  (specification->package name))

(define (lookup-inferior name)
  (define inferior
    (inferior-for-channels channels))
  (match (lookup-inferior-packages inferior name)
    ((first . rest) first)
    (_ (error
        (format #false "Could not find package `~a'.~%" name)))))

(define (p name)
  (let* ((how (if (getenv "USE_GUIX_INFERIOR")
                  lookup-inferior lookup))
         (pkg (how name)))
    `(,name ,pkg)))

(define %version
  (symbol->string (with-input-from-file "VERSION" read)))

(define-public my-package
  (package
    (name "my-package")
    (version %version)
    (source
     (string-append (getcwd) "/my-package-" version ".tar.gz"))
    (build-system gnu-build-system)
    (inputs
     (map p (list "bwa"
                  "r-minimal"
                  "r-rmarkdown"
                  "python-wrapper"
                  "python-pyyaml")))
    (native-inputs
     (map p (list "autoconf"
                  "automake")))
    (home-page "TODO")
    (synopsis "TODO")
    (description "TODO")
    (license gpl3+)))

my-package
--8<---------------cut here---------------end--------------->8---

The idea was that you would use the provided channels with

    USE_GUIX_INFERIOR=t guix environment -l guix.scm

Unfortunately, this does not work, but there also is no error.  I 
end up in an environment where none of the declared inputs are 
available.  That’s because (guix scripts environments) has no 
facilities to deal with packages that are of type 
<inferior-package>.

-- 
Ricardo