[bug#43029] [PATCH] offload: Modify the build-machine record to accept multiple systems.

[Maxim Cournoyer]

* guix/scripts/offload.scm (<build-machine>)[systems]: New field.
[system]: Accessor changed to %build-machine-system.  Default to #f.
* guix/scripts/offload.scm (build-machine-system): Wrap %build-machine-system
with a deprecation warning.
(build-machine-systems): Access the new systems field or fallback to use
build-machine-system, for backward compatibility.
(machine-matches?): Adjust.
* tests/offload.scm: Add tests...
* Makefile.am (SCM_TESTS): ...and register them.
---
 Makefile.am              |  1 +
 guix/scripts/offload.scm | 24 +++++++++++---
 tests/offload.scm        | 71 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+), 4 deletions(-)
 create mode 100644 tests/offload.scm

diff --git a/Makefile.am b/Makefile.am
index 4e50a33f82..9c38c2f83c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -433,6 +433,7 @@ SCM_TESTS =                                 \
   tests/monads.scm                             \
   tests/nar.scm                                \
   tests/networking.scm                         \
+  tests/offload.scm                            \
   tests/opam.scm                               \
   tests/openpgp.scm                            \
   tests/packages.scm                           \
diff --git a/guix/scripts/offload.scm b/guix/scripts/offload.scm
index 20ae7a9469..a56701f07a 100644
--- a/guix/scripts/offload.scm
+++ b/guix/scripts/offload.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright ?? 2014, 2015, 2016, 2017, 2018, 2019, 2020 Ludovic Court??s 
<ludo@gnu.org>
 ;;; Copyright ?? 2017 Ricardo Wurmus <rekado@elephly.net>
+;;; Copyright ?? 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -66,14 +67,16 @@
 ;;;
 ;;; Code:
 
-
 (define-record-type* <build-machine>
   build-machine make-build-machine
   build-machine?
   (name            build-machine-name)            ; string
   (port            build-machine-port             ; number
                    (default 22))
-  (system          build-machine-system)          ; string
+  (systems         %build-machine-systems         ; list of strings
+                   (default #f))                  ; drop default after system 
is removed
+  (system          %build-machine-system          ; deprecated
+                   (default #f))
   (user            build-machine-user)            ; string
   (private-key     build-machine-private-key      ; file name
                    (default (user-openssh-private-key)))
@@ -91,6 +94,19 @@
   (features        build-machine-features         ; list of strings
                    (default '())))
 
+;;; Deprecated.
+(define (build-machine-system machine)
+  (warning (G_ "The 'system' field is deprecated, \
+please use 'systems' instead.~%"))
+  (%build-machine-system machine))
+
+;;; TODO: Remove after the deprecated 'system' field is removed.
+(define (build-machine-systems machine)
+  (or (%build-machine-systems machine)
+      (list (build-machine-system machine))
+      (leave (G_ "The build-machine object lacks a value for its 'systems'
+field."))))
+
 (define-record-type* <build-requirements>
   build-requirements make-build-requirements
   build-requirements?
@@ -359,8 +375,8 @@ of free disk space on '~a'~%")
 
 (define (machine-matches? machine requirements)
   "Return #t if MACHINE matches REQUIREMENTS."
-  (and (string=? (build-requirements-system requirements)
-                 (build-machine-system machine))
+  (and (member (build-requirements-system requirements)
+               (build-machine-systems machine))
        (lset<= string=?
                (build-requirements-features requirements)
                (build-machine-features machine))))
diff --git a/tests/offload.scm b/tests/offload.scm
new file mode 100644
index 0000000000..5a5de4e8b9
--- /dev/null
+++ b/tests/offload.scm
@@ -0,0 +1,71 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright ?? 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
+;;;
+;;; 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 (tests offload)
+  #:use-module (guix scripts offload)
+  #:use-module (srfi srfi-64))
+
+
+(test-begin "offload")
+
+(define-syntax-rule (expose-internal-definitions s1 s2 ...)
+  (begin
+    (define s1 (@@ (guix scripts offload) s1))
+    (define s2 (@@ (guix scripts offload) s2)) ...))
+
+(expose-internal-definitions machine-matches?
+                             build-requirements-system
+                             build-requirements-features
+                             build-machine-system
+                             build-machine-systems
+                             %build-machine-system
+                             %build-machine-systems
+                             build-machine-features)
+
+(define (deprecated-build-machine system)
+  (build-machine
+   (name "m1")
+   (user "dummy")
+   (host-key "some-key")
+   (system system)))
+
+(define (new-build-machine systems)
+  (build-machine
+   (name "m1")
+   (user "dummy")
+   (host-key "some-key")
+   (systems systems)))
+
+;;; Test that deprecated build-machine definitions still work.
+(test-assert (machine-matches? (deprecated-build-machine "i686-linux")
+                               (build-requirements
+                                (system "i686-linux"))))
+
+
+(test-assert (machine-matches? (new-build-machine '("i686-linux"))
+                               (build-requirements
+                                (system "i686-linux"))))
+
+;;; A build machine can act as more than one system type, thanks to QEMU
+;;; emulation.
+(test-assert (machine-matches? (new-build-machine '("armhf-linux"
+                                                    "aarch64-linux"
+                                                    "i686-linux"
+                                                    "x86_64-linux"))
+                               (build-requirements
+                                (system "armhf-linux"))))
-- 
2.27.0