Add `package-transitive-inputs'; use it to honor propagated inputs.

* guix/packages.scm (package-transitive-inputs): New procedure.
  (package-derivation): Use it to compute INPUTS.

* tests/packages.scm (dummy-package): New macro.
  ("package-transitive-inputs"): New test.

guix/packages.scm

@@ -57,6 +57,7 @@ (define-module (guix packages)
             package-properties
             package-location
 
+            package-transitive-inputs
             package-source-derivation
             package-derivation
             package-cross-derivation))
@@ -161,6 +162,27 @@ (define (package-source-derivation store source)
     (($ <origin> uri method sha256 name)
      (method store uri 'sha256 sha256 name))))
 
+(define (package-transitive-inputs package)
+  "Return the transitive inputs of PACKAGE---i.e., its direct inputs along
+with their propagated inputs, recursively."
+  (let loop ((inputs (concatenate (list (package-native-inputs package)
+                                        (package-inputs package)
+                                        (package-propagated-inputs package))))
+             (result '()))
+    (match inputs
+      (()
+       (delete-duplicates (reverse result)))      ; XXX: efficiency
+      (((and i (name (? package? p) sub ...)) rest ...)
+       (let ((t (map (match-lambda
+                      ((dep-name derivation ...)
+                       (cons (string-append name "/" dep-name)
+                             derivation)))
+                     (package-propagated-inputs p))))
+         (loop (append t rest)
+               (append t (cons i result)))))
+      ((input rest ...)
+       (loop rest (cons input result))))))
+
 (define* (package-derivation store package
                              #:optional (system (%current-system)))
   "Return the derivation of PACKAGE for SYSTEM."
@@ -186,8 +208,7 @@ (define* (package-derivation store package
                           (list name
                                 (add-to-store store (basename file)
                                               #t #f "sha256" file))))
-                        (concatenate (list native-inputs inputs
+                        (package-transitive-inputs package))))
-                                           propagated-inputs)))))
        (apply builder
               store (string-append name "-" version)
               (package-source-derivation store source)

tests/packages.scm

@@ -22,6 +22,7 @@ (define-module (test-packages)
   #:use-module (guix utils)
   #:use-module (guix derivations)
   #:use-module (guix packages)
+  #:use-module (guix build-system gnu)
   #:use-module (distro)
   #:use-module (distro base)
   #:use-module (srfi srfi-26)
@@ -35,6 +36,32 @@ (define %store
 
 (test-begin "packages")
 
+(define-syntax-rule (dummy-package name* extra-fields ...)
+  (package (name name*) (version "0") (source #f)
+           (build-system gnu-build-system)
+           (description #f) (long-description #f)
+           (home-page #f)
+           extra-fields ...))
+
+(test-assert "package-transitive-inputs"
+  (let* ((a (dummy-package "a"))
+         (b (dummy-package "b"
+              (propagated-inputs `(("a" ,a)))))
+         (c (dummy-package "c"
+              (inputs `(("a" ,a)))))
+         (d (dummy-package "d"
+              (propagated-inputs `(("x" "something.drv")))))
+         (e (dummy-package "e"
+              (inputs `(("b" ,b) ("c" ,c) ("d" ,d))))))
+    (and (null? (package-transitive-inputs a))
+         (equal? `(("a" ,a)) (package-transitive-inputs b))
+         (equal? `(("a" ,a)) (package-transitive-inputs c))
+         (equal? (package-propagated-inputs d)
+                 (package-transitive-inputs d))
+         (equal? `(("b" ,b) ("b/a" ,a) ("c" ,c)
+                   ("d" ,d) ("d/x" "something.drv"))
+                 (pk 'x (package-transitive-inputs e))))))
+
 (test-skip (if (not %store) 1 0))
 
 (test-assert "GNU Hello"
@@ -63,4 +90,5 @@ (define %store
 
 ;;; Local Variables:
 ;;; eval: (put 'test-assert 'scheme-indent-function 1)
+;;; eval: (put 'dummy-package 'scheme-indent-function 1)
 ;;; End: