packages: Ensure bags are insensitive to '%current-target-system'.

Fixes a bug whereby a bag's transitive dependencies would depend on the
global '%current-target-system' value.

Partly fixes <https://issues.guix.gnu.org/41182>.

* guix/packages.scm (bag-transitive-inputs)
(bag-transitive-build-inputs, bag-transitive-target-inputs):
Parameterize '%current-target-system'.
* tests/packages.scm ("package->bag, sensitivity to %current-target-system"):
New test.

2 files changed, 19 insertions, 3 deletions

diff --git a/guix/packages.scm b/guix/packages.scm
index 9fdc679f9a..3fff50a6e8 100644
--- a/guix/packages.scm
+++ b/guix/packages.scm
@@ -814,11 +814,13 @@ dependencies are known to build on SYSTEM."
 
 (define (bag-transitive-inputs bag)
   "Same as 'package-transitive-inputs', but applied to a bag."
-  (transitive-inputs (bag-direct-inputs bag)))
+  (parameterize ((%current-target-system #f))
+    (transitive-inputs (bag-direct-inputs bag))))
 
 (define (bag-transitive-build-inputs bag)
   "Same as 'package-transitive-native-inputs', but applied to a bag."
-  (transitive-inputs (bag-build-inputs bag)))
+  (parameterize ((%current-target-system #f))
+    (transitive-inputs (bag-build-inputs bag))))
 
 (define (bag-transitive-host-inputs bag)
   "Same as 'package-transitive-target-inputs', but applied to a bag."
@@ -827,7 +829,8 @@ dependencies are known to build on SYSTEM."
 
 (define (bag-transitive-target-inputs bag)
   "Return the \"target inputs\" of BAG, recursively."
-  (transitive-inputs (bag-target-inputs bag)))
+  (parameterize ((%current-target-system (bag-target bag)))
+    (transitive-inputs (bag-target-inputs bag))))
 
 (define* (package-closure packages #:key (system (%current-system)))
   "Return the closure of PACKAGES on SYSTEM--i.e., PACKAGES and the list of
diff --git a/tests/packages.scm b/tests/packages.scm
index 7a8b5e4a2d..c528d2080c 100644
--- a/tests/packages.scm
+++ b/tests/packages.scm
@@ -1000,6 +1000,19 @@
       (("dep" package)
        (eq? package dep)))))
 
+(test-assert "package->bag, sensitivity to %current-target-system"
+  (let* ((dep (dummy-package "dep"
+                (propagated-inputs (if (%current-target-system)
+                                       `(("libxml2" ,libxml2))
+                                       '()))))
+         (pkg (dummy-package "foo"
+                (native-inputs `(("dep" ,dep)))))
+         (bag (package->bag pkg (%current-system) "foo86-hurd")))
+    (equal? (parameterize ((%current-target-system "foo64-gnu"))
+              (bag-transitive-inputs bag))
+            (parameterize ((%current-target-system #f))
+              (bag-transitive-inputs bag)))))
+
 (test-assert "bag->derivation"
   (parameterize ((%graft? #f))
     (let ((bag (package->bag gnu-make))