derivations: 'derivation' and related procedures return a single value.

* guix/derivations.scm (derivation->output-path,
  derivation->output-paths): New procedures.
  (derivation-path->output-path): Use 'derivation->output-path'.
  (derivation-path->output-paths): Use 'derivation->output-paths'.
  (derivation): Accept 'derivation?' objects as inputs.  Return a single
  value.
  (build-derivations): New procedure.
  (compiled-modules): Use 'derivation->output-paths'.
  (build-expression->derivation)[source-path]: Add case for when the
  input matches 'derivation?'.
  [prologue]: Accept 'derivation?' objects in INPUTS.
  [mod-dir, go-dir]: Use 'derivation->output-path'.
* guix/download.scm (url-fetch): Adjust to the single-value return.
* guix/packages.scm (package-output): Use 'derivation->output-path'.
* guix/scripts/build.scm (guix-build): When the argument is
  'derivation-path?', pass it through 'read-derivation'.
  Use 'derivation-file-name' to print out the .drv file names, and to
  register them.  Use 'derivation->output-path' instead of
  'derivation-path->output-path'.
* guix/scripts/package.scm (roll-back): Adjust to the single-value
  return.
  (guix-package): Use 'derivation->output-path'.
* guix/ui.scm (show-what-to-build): Adjust to deal with 'derivation?'
  objects instead of .drv file names.
* gnu/system/grub.scm (grub-configuration-file): Use
  'derivation->output-path' instead of 'derivation-path->output-path'.
* gnu/system/vm.scm (qemu-image, system-qemu-image): Likewise.
* tests/builders.scm, tests/derivations.scm, tests/packages.scm,
  tests/store.scm, tests/union.scm: Adjust to the new calling
  convention.
* doc/guix.texi (Defining Packages, The Store, Derivations): Adjust
  accordingly.

4 files changed, 19 insertions, 15 deletions

diff --git a/guix/build-system/cmake.scm b/guix/build-system/cmake.scm
index 76a9a3befe..9461b19a2e 100644
--- a/guix/build-system/cmake.scm
+++ b/guix/build-system/cmake.scm
@@ -72,9 +72,9 @@ provides a 'CMakeLists.txt' file as its build system."
   (define builder
     `(begin
        (use-modules ,@modules)
-       (cmake-build #:source ,(if (and source (derivation-path? source))
-                                 (derivation-path->output-path source)
-                                 source)
+       (cmake-build #:source ,(if (derivation? source)
+                                  (derivation->output-path source)
+                                  source)
                     #:system ,system
                     #:outputs %outputs
                     #:inputs %build-inputs
diff --git a/guix/build-system/gnu.scm b/guix/build-system/gnu.scm
index 03d56edadf..5f13f8ee29 100644
--- a/guix/build-system/gnu.scm
+++ b/guix/build-system/gnu.scm
@@ -291,8 +291,8 @@ which could lead to gratuitous input divergence."
   (define builder
     `(begin
        (use-modules ,@modules)
-       (gnu-build #:source ,(if (and source (derivation-path? source))
-                                (derivation-path->output-path source)
+       (gnu-build #:source ,(if (derivation? source)
+                                (derivation->output-path source)
                                 source)
                   #:system ,system
                   #:outputs %outputs
@@ -319,8 +319,8 @@ which could lead to gratuitous input divergence."
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ((and (? string?) (? derivation-path?))
-       guile)
+      ;; ((and (? string?) (? derivation-path?))
+      ;;  guile)
       (#f                                         ; the default
        (let* ((distro (resolve-interface '(gnu packages base)))
               (guile  (module-ref distro 'guile-final)))
@@ -438,6 +438,8 @@ platform."
        (let ()
          (define %build-host-inputs
            ',(map (match-lambda
+                   ((name (? derivation? drv) sub ...)
+                    `(,name . ,(apply derivation->output-path drv sub)))
                    ((name (? derivation-path? drv-path) sub ...)
                     `(,name . ,(apply derivation-path->output-path
                                       drv-path sub)))
@@ -447,6 +449,8 @@ platform."
 
          (define %build-target-inputs
            ',(map (match-lambda
+                   ((name (? derivation? drv) sub ...)
+                    `(,name . ,(apply derivation->output-path drv sub)))
                    ((name (? derivation-path? drv-path) sub ...)
                     `(,name . ,(apply derivation-path->output-path
                                       drv-path sub)))
@@ -454,8 +458,8 @@ platform."
                     `(,name . ,path)))
                   (append (or implicit-target-inputs '()) inputs)))
 
-         (gnu-build #:source ,(if (and source (derivation-path? source))
-                                  (derivation-path->output-path source)
+         (gnu-build #:source ,(if (derivation? source)
+                                  (derivation->output-path source)
                                   source)
                     #:system ,system
                     #:target ,target
@@ -488,8 +492,8 @@ platform."
     (match guile
       ((? package?)
        (package-derivation store guile system))
-      ((and (? string?) (? derivation-path?))
-       guile)
+      ;; ((and (? string?) (? derivation-path?))
+      ;;  guile)
       (#f                                         ; the default
        (let* ((distro (resolve-interface '(gnu packages base)))
               (guile  (module-ref distro 'guile-final)))
diff --git a/guix/build-system/perl.scm b/guix/build-system/perl.scm
index 1ff9fd2674..6661689efb 100644
--- a/guix/build-system/perl.scm
+++ b/guix/build-system/perl.scm
@@ -62,8 +62,8 @@ provides a `Makefile.PL' file as its build system."
     `(begin
        (use-modules ,@modules)
        (perl-build #:name ,name
-                   #:source ,(if (and source (derivation-path? source))
-                                 (derivation-path->output-path source)
+                   #:source ,(if (derivation? source)
+                                 (derivation->output-path source)
                                  source)
                    #:search-paths ',(map search-path-specification->sexp
                                          (append perl-search-paths
diff --git a/guix/build-system/python.scm b/guix/build-system/python.scm
index 03e587ba01..cf7ca7d3e1 100644
--- a/guix/build-system/python.scm
+++ b/guix/build-system/python.scm
@@ -120,8 +120,8 @@ provides a 'setup.py' file as its build system."
     `(begin
        (use-modules ,@modules)
        (python-build #:name ,name
-                     #:source ,(if (and source (derivation-path? source))
-                                   (derivation-path->output-path source)
+                     #:source ,(if (derivation? source)
+                                   (derivation->output-path source)
                                    source)
                      #:configure-flags ,configure-flags
                      #:system ,system