guix build: Transformations operate on single objects.

* guix/scripts/build.scm (transform-package-source): Return a procedure
that expects a single object rather than a list of packages.
(options->transformation): Rewrite to precompute the list of applicable
transformations and to return a procedure that expects a single object
rather than a list of objects.
(options->derivations): Adjust accordingly.
* tests/scripts-build.scm: New file.
* Makefile.am (SCM_TESTS): Add it.

Makefile.am

@@ -243,6 +243,7 @@ SCM_TESTS =					\
   tests/file-systems.scm			\
   tests/system.scm				\
   tests/services.scm				\
+  tests/scripts-build.scm			\
   tests/containers.scm				\
   tests/import-utils.scm
 

guix/scripts/build.scm

@@ -41,6 +41,7 @@
             set-build-options-from-command-line
             set-build-options-from-command-line*
             show-build-options-help
+            options->transformation
 
             guix-build))
 
@@ -484,39 +485,29 @@ build."
                              (set-guile-for-build (default-guile))
                              (gexp->derivation "gexp" gexp
                                                #:system system))))))
-                (transform store (options->things-to-build opts)))))
+                (map (cut transform store <>)
+                     (options->things-to-build opts)))))
 
 (define (transform-package-source sources)
-  "Return a transformation procedure that uses replaces package sources with
+  "Return a transformation procedure that replaces package sources with the
-the matching URIs given in SOURCES."
+matching URIs given in SOURCES."
   (define new-sources
     (map (lambda (uri)
            (cons (package-name->name+version (basename uri))
                  uri))
          sources))
 
-  (lambda (store packages)
+  (lambda (store obj)
-    (let loop ((packages packages)
+    (let loop ((sources  new-sources)
-               (sources  new-sources)
                (result   '()))
-      (match packages
+      (match obj
-        (()
+        ((? package? p)
-         (unless (null? sources)
-           (warning (_ "sources do not match any package:~{ ~a~}~%")
-                    (match sources
-                      (((name . uri) ...)
-                       uri))))
-         (reverse result))
-        (((? package? p) tail ...)
          (let ((source (assoc-ref sources (package-name p))))
-           (loop tail
+           (if source
-                 (alist-delete (package-name p) sources)
-                 (cons (if source
                (package-with-source store p source)
-                           p)
+               p)))
-                       result))))
+        (_
-        ((thing tail ...)
+         obj)))))
-         (loop tail sources result))))))
 
 (define %transformations
   ;; Transformations that can be applied to things to build.  The car is the
@@ -526,19 +517,33 @@ the matching URIs given in SOURCES."
   `((with-source . ,transform-package-source)))
 
 (define (options->transformation opts)
-  "Return a procedure that, when passed a list of things to build (packages,
+  "Return a procedure that, when passed an object to build (package,
-derivations, etc.), applies the transformations specified by OPTS."
+derivation, etc.), applies the transformations specified by OPTS."
-  (apply compose
+  (define applicable
-         (map (match-lambda
+    ;; List of applicable transformations as symbol/procedure pairs.
+    (filter-map (match-lambda
                   ((key . transform)
-                 (let ((args (filter-map (match-lambda
+                   (match (filter-map (match-lambda
                                         ((k . arg)
                                          (and (eq? k key) arg)))
-                                         opts)))
+                                      opts)
-                   (if (null? args)
+                     (()   #f)
-                       (lambda (store things) things)
+                     (args (cons key (transform args))))))
-                       (transform args)))))
+                %transformations))
-              %transformations)))
+
+  (lambda (store obj)
+    (fold (match-lambda*
+            (((name . transform) obj)
+             (let ((new (transform store obj)))
+               (when (eq? new obj)
+                 (warning (_ "transformation '~a' had no effect on ~a~%")
+                          name
+                          (if (package? obj)
+                              (package-full-name obj)
+                              obj)))
+               new)))
+          obj
+          applicable)))
 
 (define (show-build-log store file urls)
   "Show the build log for FILE, falling back to remote logs from URLS if

tests/scripts-build.scm

@@ -0,0 +1,65 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (test-scripts-build)
+  #:use-module (guix tests)
+  #:use-module (guix store)
+  #:use-module (guix packages)
+  #:use-module (guix scripts build)
+  #:use-module (guix ui)
+  #:use-module (srfi srfi-64))
+
+
+(test-begin "scripts-build")
+
+(test-assert "options->transformation, no transformations"
+  (let ((p (dummy-package "foo"))
+        (t (options->transformation '())))
+    (with-store store
+      (eq? (t store p) p))))
+
+(test-assert "options->transformation, with-source"
+  ;; Our pseudo-package is called 'guix.scm' so the 'guix.scm' source should
+  ;; be applicable.
+  (let* ((p (dummy-package "guix.scm"))
+         (s (search-path %load-path "guix.scm"))
+         (t (options->transformation `((with-source . ,s)))))
+    (with-store store
+      (let ((new (t store p)))
+        (and (not (eq? new p))
+             (string=? (package-source new)
+                       (add-to-store store "guix.scm" #t
+                                     "sha256" s)))))))
+
+(test-assert "options->transformation, with-source, no matches"
+  ;; When a transformation in not applicable, a warning must be raised.
+  (let* ((p (dummy-package "foobar"))
+         (s (search-path %load-path "guix.scm"))
+         (t (options->transformation `((with-source . ,s)))))
+    (with-store store
+      (let* ((port (open-output-string))
+             (new  (parameterize ((guix-warning-port port))
+                     (t store p))))
+        (and (eq? new p)
+             (string-contains (get-output-string port)
+                              "had no effect"))))))
+
+(test-end)
+
+
+(exit (= (test-runner-fail-count (test-runner-current)) 0))