derivations: Add #:dependency-graphs `derivation' parameter.

* guix/derivations.scm (derivation): Add `dependency-graphs' keyword
  parameter; honor it.
* tests/derivations.scm (bootstrap-binary): New procedure.
  (%bash): Use it.
  (%mkdir): New variable.
  (directory-contents): Add `slurp' optional parameter.
  ("derivation with #:dependency-graphs"): New test.
* doc/guix.texi (Derivations): Update accordingly.

1 files changed, 24 insertions, 4 deletions

diff --git a/guix/derivations.scm b/guix/derivations.scm
index 3d7a30aaa8..fea9984370 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -501,11 +501,16 @@ the derivation called NAME with hash HASH."
                      #:key
                      (system (%current-system)) (env-vars '())
                      (inputs '()) (outputs '("out"))
-                     hash hash-algo hash-mode)
+                     hash hash-algo hash-mode
+                     dependency-graphs)
   "Build a derivation with the given arguments.  Return the resulting
 store path and <derivation> object.  When HASH, HASH-ALGO, and HASH-MODE
 are given, a fixed-output derivation is created---i.e., one whose result is
-known in advance, such as a file download."
+known in advance, such as a file download.
+
+When DEPENDENCY-GRAPHS is true, it must be a list of file name/store path
+pairs.  In that case, the reference graph of each store path is exported in
+the build environment in the corresponding file, in a simple text format."
   (define direct-store-path?
     (let ((len (+ 1 (string-length (%store-prefix)))))
       (lambda (p)
@@ -540,7 +545,22 @@ known in advance, such as a file download."
                                            value))))
                                env-vars))))))
 
-  (define (env-vars-with-empty-outputs)
+  (define (user+system-env-vars)
+    ;; Some options are passed to the build daemon via the env. vars of
+    ;; derivations (urgh!).  We hide that from our API, but here is the place
+    ;; where we kludgify those options.
+    (match dependency-graphs
+      (((file . path) ...)
+       (let ((value (map (cut string-append <> " " <>)
+                         file path)))
+         ;; XXX: This all breaks down if an element of FILE or PATH contains
+         ;; white space.
+         `(("exportReferencesGraph" . ,(string-join value " "))
+           ,@env-vars)))
+      (#f
+       env-vars)))
+
+  (define (env-vars-with-empty-outputs env-vars)
     ;; Return a variant of ENV-VARS where each OUTPUTS is associated with an
     ;; empty string, even outputs that do not appear in ENV-VARS.
     (let ((e (map (match-lambda
@@ -572,7 +592,7 @@ known in advance, such as a file download."
                                                       #t "sha256" input)))
                               (make-derivation-input path '()))))
                           (delete-duplicates inputs)))
-         (env-vars   (env-vars-with-empty-outputs))
+         (env-vars   (env-vars-with-empty-outputs (user+system-env-vars)))
          (drv-masked (make-derivation outputs
                                       (filter (compose derivation-path?
                                                        derivation-input-path)