Re: [PATCH] Improve shell script headers and pre-inst-env handling

[Mark H Weaver <mhw@netris.org>]

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Hi Ludovic,

ludo@gnu.org (Ludovic Courtès) writes:
> Note that I think we’ll most likely have a single ‘guix’ script in the
> near future, so that ‘guix-pull’ can actually update everything: Guix,
> commands, and distro.

Okay, I have another proposal.  I've written a proposed 'guix' script
that's pure Guile code.  The idea is that "guix FOO ARGS ..." augments
the load paths as needed, loads the module (guix scripts guix-FOO) and
then applies the procedure 'guix-FOO' to (ARGS ...)

It also supports "guix-FOO ARGS ..." simply by making 'guix-FOO' a
symlink to 'guix'.

Then we can move all the scripts into guix/scripts/, and remove the
boilerplate shell code from the top of all them.  They become pure guile
modules.  No more shell at all.

What do you think?

    Mark


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#!@GUILE@ -s
-*- scheme -*-
!#
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013 Mark H Weaver <mhw@netris.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(use-modules (ice-9 regex))

(let ()
  (define-syntax-rule (push! elt v) (set! v (cons elt v)))

  (define config-lookup
    (let ((config '(("prefix"         . "@prefix@")
                    ("datarootdir"    . "@datarootdir@")
                    ("guilemoduledir" . "@guilemoduledir@")))
          (var-ref-regexp (make-regexp "\\$\\{([a-z]+)\\}")))
      (define (expand-var-ref match)
        (lookup (match:substring match 1)))
      (define (expand str)
        (regexp-substitute/global #f var-ref-regexp str
                                  'pre expand-var-ref 'post))
      (define (lookup name)
        (expand (assoc-ref config name)))
      lookup))

  (define (maybe-augment-load-paths!)
    (unless (getenv "GUIX_UNINSTALLED")
      (let ((module-dir (config-lookup "guilemoduledir")))
        (push! module-dir %load-path)
        (push! module-dir %load-compiled-path))))

  (define (run-script name args)
    (let* ((symbol (string->symbol name))
           (module (resolve-interface `(guix scripts ,symbol)))
           (script (module-ref module symbol)))
      (apply script args)))

  (define (main arg0 . args)
    (setlocale LC_ALL "")  ; XXX Is there a reason not to do this?
    (maybe-augment-load-paths!)
    (let ((cmd (basename arg0)))
      (cond ((string-prefix? "guix-" cmd)
             (run-script cmd args))
            ((not (null? args))
             (run-script (string-append "guix-" (car args))
                         (cdr args)))
            (else
             ;; TODO: Dynamically generate a summary of available commands.
             (format (current-error-port)
                     "Usage: guix <command> [<args>]~%")
             (exit 1)))))

  (apply main (command-line)))