Re: Guix and Emacs Integration for Polyglot Development

[Jan Nieuwenhuizen <janneke@gnu.org>]

Ludovic Courtès writes:

> In all modesty ;-) I think the API is rather good:
>
> scheme@(guile-user)> ,use(guix profiles)
> scheme@(guile-user)> (profile-search-paths "/home/ludo/.guix-profile")
> $11 = ((#<<search-path-specification> variable: "PATH" files: ("bin" "sbin") separator: ":" file-type: directory file-pattern: #f> . "/home/ludo/.guix-profile/bin:/home/ludo/.guix-profile/sbin") (#<<search-path-specification> variable: "PYTHONPATH" files: ("lib/python3.6/site-packages") separator: ":" file-type: directory file-pattern: #f> . "/home/ludo/.guix-profile/lib/python3.6/site-packages") …

Whoa, that helps!  Is it just me who is so dense -- I really think this
REPL'y power of Guix is much under-appreciated and would deserve
more attention.

So, what about (thanks to Ricardo via #guile irc and wasamasa via #emacs)

--8<---------------cut here---------------start------------->8---
(defun guix-switch-profile (&optional profile)
  "Switch Emacs' environment to PROFILE.  PROFILE can be a named
profile (like ~/.guix-profile, ~/.config/guix/work) or an
environment (like: echo $GUIX_ENVIRONMENT)."

  (interactive "fprofile: ")
  (lexical-let* ((guix-program
                  `(begin
                    (use-modules (ice-9 match)
                                 (guix profiles)
                                 (guix search-paths))
                    (let ((specs (profile-search-paths ,(expand-file-name profile))))
                      (map
                       (match-lambda ((spec . dir)
                                      (list (search-path-specification-variable spec)
                                            (or (search-path-specification-separator spec) "")
                                            dir)))
                       specs))))
                 (guix-output (guix-eval (format "%S" guix-program)))
                 (profile-sexp (car (read-from-string (car guix-output)))))
    (mapcar*
     (lambda (variable separator path)
       (lexical-let ((value (cond ((string-empty-p separator) path)
                                  ((getenv variable) (concat path separator (getenv variable)))
                                  (t path))))
         (setenv variable value)))
     (mapcar #'car profile-sexp)
     (mapcar #'cadr profile-sexp)
     (mapcar #'caddr profile-sexp))))
--8<---------------cut here---------------end--------------->8---

and where to put this?

janneke