build-system: Introduce "bags" as an intermediate representation.

* guix/build-system.scm (<build-system>)[build, cross-build]: Remove.
  [lower]: New field.
  (<bag>): New record type.
  (make-bag): New procedure.
* guix/packages.scm (bag-transitive-inputs, bag-transitive-build-inputs,
  bag-transitive-host-inputs, bag-transitive-target-inputs,
  package->bag): New procedures.
  (package-derivation): Use it; use the bag, apply its build procedure,
  etc.
  (package-cross-derivation): Likewise.
* gnu/packages/bootstrap.scm (raw-build, make-raw-bag): New procedure.
  (%bootstrap-guile): Use them.
* guix/build-system/trivial.scm (lower): New procedure.
  (trivial-build, trivial-cross-build): Remove 'source' parameter.  Pass
  INPUTS as is.
  (trivial-build-system): Adjust accordingly.
* guix/build-system/gnu.scm (%store, inputs-search-paths,
  standard-search-paths, expand-inputs, standard-inputs): Remove.
  (gnu-lower): New procedure.
  (gnu-build): Remove 'source' and #:implicit-inputs? parameters.
  Remove 'implicit-inputs' and 'implicit-search-paths' variables.  Get
  the source from INPUT-DRVS.
  (gnu-cross-build): Likewise.
  (standard-cross-packages): Remove call to 'standard-packages'.
  (standard-cross-inputs, standard-cross-search-paths): Remove.
  (gnu-build-system): Remove 'build' and 'cross-build'; add 'lower'.
* guix/build-system/cmake.scm (lower): New procedure.
  (cmake-build): Remove 'source' and #:cmake parameters.  Use INPUTS and
  SEARCH-PATHS as is.  Get the source from INPUTS.
* guix/build-system/perl.scm: Likewise.
* guix/build-system/python.scm: Likewise.
* guix/build-system/ruby.scm: Likewise.
* gnu/packages/cross-base.scm (cross-gcc): Change "cross-linux-headers"
  to "linux-headers".
  (cross-libc)[xlinux-headers]: Pass #:implicit-cross-inputs? #f.
  Likewise.  In 'propagated-inputs', change "cross-linux-headers" to
  "linux-headers".
* guix/git-download.scm (git-fetch): Use 'standard-packages' instead of
  'standard-inputs'.
* tests/builders.scm ("gnu-build-system"): Remove use of
  'build-system-builder'.
  ("gnu-build"): Remove 'source' and #:implicit-inputs? arguments to
  'gnu-build'.
* tests/packages.scm ("search paths"): Adjust to new build system API.
  ("package-cross-derivation, no cross builder"): Likewise.
* doc/guix.texi (Build Systems): Add paragraph on bags.

1 files changed, 44 insertions, 32 deletions

diff --git a/guix/build-system/python.scm b/guix/build-system/python.scm
index a90e7ff511..e28573bb05 100644
--- a/guix/build-system/python.scm
+++ b/guix/build-system/python.scm
@@ -92,9 +92,33 @@ prepended to the name."
 (define package-with-python2
   (cut package-with-explicit-python <> (default-python2) "python-" "python2-"))
 
-(define* (python-build store name source inputs
+(define* (lower name
+                #:key source inputs native-inputs outputs target
+                (python (default-python))
+                #:allow-other-keys
+                #:rest arguments)
+  "Return a bag for NAME."
+  (define private-keywords
+    '(#:source #:target #:python #:inputs #:native-inputs))
+
+  (and (not target)                               ;XXX: no cross-compilation
+       (bag
+         (name name)
+         (host-inputs `(,@(if source
+                              `(("source" ,source))
+                              '())
+                        ,@inputs
+
+                        ;; Keep the standard inputs of 'gnu-build-system'.
+                        ,@(standard-packages)))
+         (build-inputs `(("python" ,python)
+                         ,@native-inputs))
+         (outputs outputs)
+         (build python-build)
+         (arguments (strip-keyword-arguments private-keywords arguments)))))
+
+(define* (python-build store name inputs
                        #:key
-                       (python (default-python))
                        (tests? #t)
                        (test-target "test")
                        (configure-flags ''())
@@ -111,18 +135,17 @@ prepended to the name."
                                   (guix build utils))))
   "Build SOURCE using PYTHON, and with INPUTS.  This assumes that SOURCE
 provides a 'setup.py' file as its build system."
-
-  (define python-search-paths
-    (append (package-native-search-paths python)
-            (standard-search-paths)))
-
   (define builder
     `(begin
        (use-modules ,@modules)
        (python-build #:name ,name
-                     #:source ,(if (derivation? source)
-                                   (derivation->output-path source)
-                                   source)
+                     #:source ,(match (assoc-ref inputs "source")
+                                 (((? derivation? source))
+                                  (derivation->output-path source))
+                                 ((source)
+                                  source)
+                                 (source
+                                  source))
                      #:configure-flags ,configure-flags
                      #:system ,system
                      #:test-target ,test-target
@@ -130,8 +153,7 @@ provides a 'setup.py' file as its build system."
                      #:phases ,phases
                      #:outputs %outputs
                      #:search-paths ',(map search-path-specification->sexp
-                                           (append python-search-paths
-                                                   search-paths))
+                                           search-paths)
                      #:inputs %build-inputs)))
 
   (define guile-for-build
@@ -143,27 +165,17 @@ provides a 'setup.py' file as its build system."
               (guile  (module-ref distro 'guile-final)))
          (package-derivation store guile system)))))
 
-  (let ((python (package-derivation store python system)))
-    (build-expression->derivation store name builder
-                                  #:inputs
-                                  `(,@(if source
-                                          `(("source" ,source))
-                                          '())
-                                    ("python" ,python)
-                                    ,@inputs
-
-                                    ;; Keep the standard inputs of
-                                    ;; 'gnu-build-system'.
-                                    ,@(standard-inputs system))
-
-                                  #:system system
-                                  #:modules imported-modules
-                                  #:outputs outputs
-                                  #:guile-for-build guile-for-build)))
+  (build-expression->derivation store name builder
+                                #:inputs inputs
+                                #:system system
+                                #:modules imported-modules
+                                #:outputs outputs
+                                #:guile-for-build guile-for-build))
 
 (define python-build-system
-  (build-system (name 'python)
-                (description "The standard Python build system")
-                (build python-build)))
+  (build-system
+    (name 'python)
+    (description "The standard Python build system")
+    (lower lower)))
 
 ;;; python.scm ends here