;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2022 Mathieu Othacehe <othacehe@gnu.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/>.

(define-module (gnu compression)
  #:use-module (guix gexp)
  #:use-module (guix ui)
  #:use-module ((gnu packages compression) #:hide (zip))
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (ice-9 match)
  #:export (compressor
            compressor?
            compressor-name
            compressor-extension
            compressor-command
            %compressors
            lookup-compressor))

;; Type of a compression tool.
(define-record-type <compressor>
  (compressor name extension command)
  compressor?
  (name       compressor-name)      ;string (e.g., "gzip")
  (extension  compressor-extension) ;string (e.g., ".lz")
  (command    compressor-command))  ;gexp (e.g., #~(list "/gnu/store/…/gzip"
                                    ;                    "-9n" ))

(define %compressors
  ;; Available compression tools.
  (list (compressor "gzip"  ".gz"
                    #~(list #+(file-append gzip "/bin/gzip") "-9n"))
        (compressor "lzip"  ".lz"
                    #~(list #+(file-append lzip "/bin/lzip") "-9"))
        (compressor "xz"    ".xz"
                    #~(append (list #+(file-append xz "/bin/xz")
                                    "-e")
                              (%xz-parallel-args)))
        (compressor "bzip2" ".bz2"
                    #~(list #+(file-append bzip2 "/bin/bzip2") "-9"))
        (compressor "zstd" ".zst"
                    ;; The default level 3 compresses better than gzip in a
                    ;; fraction of the time, while the highest level 19
                    ;; (de)compresses more slowly and worse than xz.
                    #~(list #+(file-append zstd "/bin/zstd") "-3"
                            (format #f "--threads=~a" (parallel-job-count))))
        (compressor "none" "" #f)))

(define (lookup-compressor name)
  "Return the compressor object called NAME.  Error out if it could not be
found."
  (or (find (match-lambda
              (($ <compressor> name*)
               (string=? name* name)))
            %compressors)
      (leave (G_ "~a: compressor not found~%") name)))
st-channel-instances’ would perform a depth-first
traversal of channels.  Since dependencies specified in ‘.guix-channel’
are usually less specific that those provided by the user, this would
lead to the use of instances corresponding to those less specific specs,
which in turn might declare dependencies that do not exist for the more
specific instances.

This commit changes ‘latest-channel-instances’ to perform a
breadth-first traversal, thereby giving user-supplied channels higher
precedence over dependencies found via ‘.guix-channel’.

Fixes &lt;https://issues.guix.gnu.org/68822&gt;.

* guix/channels.scm (latest-channel-instances)[ignore?]: Remove.
[instance-name, same-named?, more-specific?]: New procedures.
Rewrite as a breadth-first traversal using a regular loop.
* tests/channels.scm ("latest-channel-instances reads dependencies from most-specific instance"):
New test.

Change-Id: Iba518145cfd209f04293a56246dbfee3b714650b
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2024-01-31 09:07:25 +0100'>2024-01-31</span></td><td><a href='/guix/commit/tests/channels.scm?id=36d654fa540539413b88cf8ec62a0fb55280f820'>channels: Tweak test.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/channels.scm ("latest-channel-instances excludes duplicate channel dependencies"):
Use ‘equal?’ rather than ‘string=?’ since we can get #f.

Change-Id: I437b9d7e23200cf0c98b1593e68b1d355bc2de01
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-09-26 17:36:59 +0200'>2023-09-26</span></td><td><a href='/guix/commit/tests/channels.scm?id=ba21eeb565fe414b3647173068a0f3eadd174c06'>tests: Assume ‘git’ is always available.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/channels.scm (gpg+git-available?): Check for ‘gpg-command’
only.
Remove all ‘test-skip’ statements.
* tests/derivations.scm: Likewise.
* tests/git-authenticate.scm: Likewise.
* tests/git.scm: Likewise.
* tests/import-git.scm: Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>