Subject: [bug#69940] [PATCH 1/2] build-system/channel: Add support for additional channels.

From: Ludovic Courtès <[email-masked]>
Date: Fri, 22 Mar 2024 15:12:29 +0100

Until now, ‘channel-build-system’ would assume a single channel, the
‘guix’ channel.  This change lets users specify additional channels
using the #:channels parameter.

* guix/build-system/channel.scm (build-channels): Add #:channels and
honor it.
(channel-build-system): In ‘lower’, add #:channels and honor it.
* doc/guix.texi (Build Systems): Document it.

Change-Id: I36c1d19cbeee02a4d1144de089b78df0390774a0
---
 doc/guix.texi                 | 5 ++++-
 guix/build-system/channel.scm | 7 +++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index eda4084e7f..07dc6e24a8 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -10451,7 +10451,10 @@ Build Systems
 name, in which case an additional @code{#:commit} argument must be
 supplied to specify the commit being built (a hexadecimal string).
 
-The resulting package is a Guix instance of the given channel, similar
+Optionally, a @code{#:channels} argument specifying additional channels
+can be provided.
+
+The resulting package is a Guix instance of the given channel(s), similar
 to how @command{guix time-machine} would build it.
 @end defvar
 
diff --git a/guix/build-system/channel.scm b/guix/build-system/channel.scm
index 6ad377f930..0607dcf4d7 100644
--- a/guix/build-system/channel.scm
+++ b/guix/build-system/channel.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2019-2022 Ludovic Courtès <[email-masked]>
+;;; Copyright © 2019-2022, 2024 Ludovic Courtès <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -37,6 +37,7 @@ (define latest-channel-instances*
 
 (define* (build-channels name inputs
                          #:key source system commit
+                         (channels '())
                          (authenticate? #t)
                          #:allow-other-keys)
   (mlet* %store-monad ((instances
@@ -44,7 +45,7 @@ (define* (build-channels name inputs
                                (return (list source)))
                               ((channel? source)
                                (latest-channel-instances*
-                                (list source)
+                                (cons source channels)
                                 #:authenticate? authenticate?))
                               ((string? source)
                                ;; If SOURCE is a store file name, as is the
@@ -64,12 +65,14 @@ (define* (build-channels name inputs
 (define channel-build-system
   ;; Build system used to "convert" a channel instance to a package.
   (let ((lower (lambda* (name #:key system source commit (authenticate? #t)
+                              (channels '())
                               #:allow-other-keys)
                  (bag
                    (name name)
                    (system system)
                    (build build-channels)
                    (arguments `(#:source ,source
+                                #:channels ,channels
                                 #:authenticate? ,authenticate?
                                 #:commit ,commit))))))
     (build-system (name 'channel)
-- 
2.41.0