gnu: bootloader: Support multiple targets.

Fixes <https://issues.guix.gnu.org/40997>.

* gnu/bootloader.scm (<bootloader-configuration>): New 'targets' field.
(%bootloader-configuration-target): New procedure.
(bootloader-configuration-target): Add deprecation warning.
(bootloader-configuration-targets): New procedure.
* guix/scripts/system.scm (install): Access targets via
bootloader-configuration-targets.
(perform-action)[bootloader-target]: Remove unused argument and update doc.
Access targets via bootloader-configuration-targets and fix indentation.
(process-action): Access targets via bootloader-configuration-targets.
Do not provide the unused BOOTLOADER-TARGET argument when applying
`perform-action'.
* guix/scripts/system/reconfigure.scm (install-bootloader-program): Rename
DEVICE argument to DEVICES.  Adjust doc and comment.  Apply `installer' and
`disk-installer' for every DEVICES.
(install-bootloader): Access targets via bootloader-configuration-targets and
rename variable from DEVICE to DEVICES.
* gnu/tests/install.scm: Adjust accordingly.
* tests/guix-system.sh: Likewise.
* gnu/tests/reconfigure.scm (run-install-bootloader-test): Adjust the DEVICES
argument so that it is a list.
* doc/guix.texi: Update doc.

3 files changed, 34 insertions, 16 deletions

diff --git a/gnu/bootloader.scm b/gnu/bootloader.scm
index 6d7352ddd2..98807a4810 100644
--- a/gnu/bootloader.scm
+++ b/gnu/bootloader.scm
@@ -55,7 +55,8 @@
             bootloader-configuration
             bootloader-configuration?
             bootloader-configuration-bootloader
-            bootloader-configuration-target
+            bootloader-configuration-target ;deprecated
+            bootloader-configuration-targets
             bootloader-configuration-menu-entries
             bootloader-configuration-default-entry
             bootloader-configuration-timeout
@@ -183,7 +184,9 @@ record."
   bootloader-configuration make-bootloader-configuration
   bootloader-configuration?
   (bootloader         bootloader-configuration-bootloader) ;<bootloader>
-  (target             bootloader-configuration-target      ;string
+  (targets            %bootloader-configuration-targets    ;list of strings
+                      (default #f))
+  (target             %bootloader-configuration-target ;deprecated
                       (default #f))
   (menu-entries       bootloader-configuration-menu-entries ;list of <menu-entry>
                       (default '()))
@@ -204,6 +207,21 @@ record."
   (serial-speed       bootloader-configuration-serial-speed ;integer | #f
                       (default #f)))
 
+;;; Deprecated.
+(define (bootloader-configuration-target config)
+  (warning (G_ "the 'target' field is deprecated, please use 'targets' \
+instead~%"))
+  (%bootloader-configuration-target config))
+
+(define (bootloader-configuration-targets config)
+  (or (%bootloader-configuration-targets config)
+      ;; TODO: Remove after the deprecated 'target' field is removed.
+      (list (bootloader-configuration-target config))
+      ;; XXX: At least the GRUB installer (see (gnu bootloader grub)) has this
+      ;; peculiar behavior of installing fonts and GRUB modules when DEVICE is #f,
+      ;; hence the default value of '(#f) rather than '().
+      (list #f)))
+
 
 ;;;
 ;;; Bootloaders.
diff --git a/gnu/tests/install.scm b/gnu/tests/install.scm
index 80604361e0..d7fafd210c 100644
--- a/gnu/tests/install.scm
+++ b/gnu/tests/install.scm
@@ -4,7 +4,7 @@
 ;;; Copyright © 2020 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2020 Danny Milosavljevic <dannym@scratchpost.org>
 ;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
-;;; Copyright © 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+;;; Copyright © 2020, 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -97,7 +97,7 @@
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons (file-system
                           (device (file-system-label "my-root"))
@@ -135,7 +135,7 @@
 
     (bootloader (bootloader-configuration
                  (bootloader extlinux-bootloader-gpt)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons (file-system
                           (device (file-system-label "my-root"))
@@ -418,7 +418,7 @@ per %test-installed-os, this test is expensive in terms of CPU and storage.")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vda")))
+                 (targets (list "/dev/vda"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons (file-system
                           (device (file-system-label "my-root"))
@@ -549,7 +549,7 @@ partition.  In particular, home directories must be correctly created (see
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons* (file-system
                            (device (file-system-label "root-fs"))
@@ -626,7 +626,7 @@ where /gnu lives on a separate partition.")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
 
     ;; Add a kernel module for RAID-1 (aka. "mirror").
@@ -842,7 +842,7 @@ build (current-guix) and then store a couple of full system images.")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
 
     (mapped-devices (list (mapped-device
@@ -929,7 +929,7 @@ reboot\n")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
 
     (mapped-devices (list (mapped-device
                            (source
@@ -1029,7 +1029,7 @@ store a couple of full system images.")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons (file-system
                           (device (file-system-label "my-root"))
@@ -1103,7 +1103,7 @@ build (current-guix) and then store a couple of full system images.")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
 
     (file-systems (cons (file-system
@@ -1171,7 +1171,7 @@ RAID-0 (stripe) root partition.")
     (locale "en_US.UTF-8")
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons* (file-system
                            (device (file-system-label "btrfs-pool"))
@@ -1264,7 +1264,7 @@ build (current-guix) and then store a couple of full system images.")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons (file-system
                           (device (file-system-label "my-root"))
@@ -1337,7 +1337,7 @@ build (current-guix) and then store a couple of full system images.")
 
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
-                 (target "/dev/vdb")))
+                 (targets (list "/dev/vdb"))))
     (kernel-arguments '("console=ttyS0"))
     (file-systems (cons (file-system
                           (device (file-system-label "my-root"))
diff --git a/gnu/tests/reconfigure.scm b/gnu/tests/reconfigure.scm
index 52beeef447..001b5d185a 100644
--- a/gnu/tests/reconfigure.scm
+++ b/gnu/tests/reconfigure.scm
@@ -261,7 +261,7 @@ bootloader's configuration file."
      ;; would attempt to write directly to the virtual disk if the
      ;; installation script were run.
      (test
-      (install-bootloader-program #f #f #f bootcfg bootcfg-file #f "/")))))
+      (install-bootloader-program #f #f #f bootcfg bootcfg-file '(#f) "/")))))
 
 
 (define %test-switch-to-system