guix: package: Fix recutils output for non-package inputs.

* guix/ui.scm (package->recutils)[dependencies]: Ignore non-package inputs.
* tests/guix-package.sh: New test.

guix/ui.scm

@@ -468,8 +468,8 @@ WIDTH columns."
   (format port "version: ~a~%" (package-version p))
   (format port "dependencies: ~a~%"
           (match (package-direct-inputs p)
-            (((labels packages . _) ...)
-             (dependencies->recutils packages))))
+            (((labels inputs . _) ...)
+             (dependencies->recutils (filter package? inputs)))))
   (format port "location: ~a~%"
           (or (and=> (package-location p) location->string)
               (_ "unknown")))

tests/guix-package.sh

@@ -179,6 +179,9 @@ guix package -p "$profile" -A 'gui.*e' | grep guile
 # Check whether `--show' returns something sensible.
 guix package --show=guile | grep "^name: guile"
 
+# Check show doesn't fail for packages with non-package inputs.
+guix package --show=texlive
+
 # There's no generation older than 12 months, so the following command should
 # have no effect.
 generation="`readlink_base "$profile"`"