packages: 'supported-package?' binds '%current-system' for graph traversal.

Previously, (supported-package? coreutils "armhf-linux")
with (%current-system) = "x86_64-linux" would return false.  That's
because 'supported-package?' would traverse the x86_64 dependency graph,
which contains 'tcc-boot0', which supports x86 only.

Consequently, 'supported-package?' would match only 53 packages for
"armhf-linux" when running on x86, as is the case during continuous
integration.

* guix/packages.scm (package-transitive-supported-systems): Add an
optional 'system' parameter.  Use 'mlambda' instead of 'mlambdaq' for
memoization.
(supported-package?): Pass 'system' to 'package-transitive-supported-systems'.
* tests/packages.scm ("package-transitive-supported-systems, implicit inputs")
("package-transitive-supported-systems: reduced binary seed, implicit inputs"):
Remove calls to 'invalidate-memoization!', which no longer work and were
presumably introduced to work around the bug we're fixing (see commit
0db65c168fd6dec57a357735fe130c80feba5460).
* tests/packages.scm ("supported-package?"): Rewrite test to use only
existing system name since otherwise 'bootstrap-executable' raises an
exception.
("supported-package? vs. system-dependent graph"): New test.

1 files changed, 18 insertions, 12 deletions

diff --git a/guix/packages.scm b/guix/packages.scm
index d9eeee15a2..39ab28d807 100644
--- a/guix/packages.scm
+++ b/guix/packages.scm
@@ -767,23 +767,29 @@ in INPUTS and their transitive propagated inputs."
        (transitive-inputs inputs)))
 
 (define package-transitive-supported-systems
-  (mlambdaq (package)
-    "Return the intersection of the systems supported by PACKAGE and those
+  (let ()
+    (define supported-systems
+      (mlambda (package system)
+        (parameterize ((%current-system system))
+          (fold (lambda (input systems)
+                  (match input
+                    ((label (? package? package) . _)
+                     (lset-intersection string=? systems
+                                        (supported-systems package system)))
+                    (_
+                     systems)))
+                (package-supported-systems package)
+                (bag-direct-inputs (package->bag package))))))
+
+    (lambda* (package #:optional (system (%current-system)))
+      "Return the intersection of the systems supported by PACKAGE and those
 supported by its dependencies."
-    (fold (lambda (input systems)
-            (match input
-              ((label (? package? p) . _)
-               (lset-intersection
-                string=? systems (package-transitive-supported-systems p)))
-              (_
-               systems)))
-          (package-supported-systems package)
-          (bag-direct-inputs (package->bag package)))))
+      (supported-systems package system))))
 
 (define* (supported-package? package #:optional (system (%current-system)))
   "Return true if PACKAGE is supported on SYSTEM--i.e., if PACKAGE and all its
 dependencies are known to build on SYSTEM."
-  (member system (package-transitive-supported-systems package)))
+  (member system (package-transitive-supported-systems package system)))
 
 (define (bag-direct-inputs bag)
   "Same as 'package-direct-inputs', but applied to a bag."