gexp: Aggregate outputs of compound gexps.

* guix/gexp.scm (gexp-outputs)[add-reference-output]: Recurse into
  lists.
* tests/gexp.scm ("output list + ungexp-splicing list, combined gexps"):
  New test.

2 files changed, 13 insertions, 3 deletions

diff --git a/guix/gexp.scm b/guix/gexp.scm
index a8349c7d6e..1f64cf75ae 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -314,12 +314,12 @@ references."
        (cons name result))
       ((? gexp? exp)
        (append (gexp-outputs exp) result))
+      ((lst ...)
+       (fold-right add-reference-output result lst))
       (_
        result)))
 
-  (fold-right add-reference-output
-              '()
-              (gexp-references exp)))
+  (add-reference-output (gexp-references exp) '()))
 
 (define* (gexp->sexp exp #:key
                      (system (%current-system))
diff --git a/tests/gexp.scm b/tests/gexp.scm
index a6fb550540..2ec6c8e3ef 100644
--- a/tests/gexp.scm
+++ b/tests/gexp.scm
@@ -230,6 +230,16 @@
                 (gexp-outputs exp2))
          (= 2 (length (gexp-outputs exp2))))))
 
+(test-assert "output list + ungexp-splicing list, combined gexps"
+  (let* ((exp0  (gexp (mkdir (ungexp output))))
+         (exp1  (gexp (mkdir (ungexp output "foo"))))
+         (exp2  (gexp (begin (display "hi!")
+                             (ungexp-splicing (list exp0 exp1))))))
+    (and (lset= equal?
+                (append (gexp-outputs exp0) (gexp-outputs exp1))
+                (gexp-outputs exp2))
+         (= 2 (length (gexp-outputs exp2))))))
+
 (test-assertm "gexp->file"
   (mlet* %store-monad ((exp -> (gexp (display (ungexp %bootstrap-guile))))
                        (guile  (package-file %bootstrap-guile))