derivations: Add properties.

* guix/derivations.scm (derivation): Add #:properties parameter.
[user+system-env-vars]: Honor it.
(derivation-properties): New procedure.
(build-expression->derivation): Add #:properties and pass it to
'derivation'.
* guix/gexp.scm (gexp->derivation): Likewise.
* tests/derivations.scm ("derivation-properties"): New test.
* tests/gexp.scm ("gexp->derivation properties"): New test.
* doc/guix.texi (Derivations, G-Expressions): Adjust accordingly.

doc/guix.texi

@@ -5060,7 +5060,7 @@ a derivation is the @code{derivation} procedure:
   [#:system (%current-system)] [#:references-graphs #f] @
   [#:allowed-references #f] [#:disallowed-references #f] @
   [#:leaked-env-vars #f] [#:local-build? #f] @
-  [#:substitutable? #t]
+  [#:substitutable? #t] [#:properties '()]
 Build a derivation with the given arguments, and return the resulting
 @code{<derivation>} object.
 
@@ -5097,6 +5097,9 @@ When @var{substitutable?} is false, declare that substitutes of the
 derivation's output should not be used (@pxref{Substitutes}).  This is
 useful, for instance, when building packages that capture details of the
 host CPU instruction set.
+
+@var{properties} must be an association list describing ``properties'' of the
+derivation.  It is kept as-is, uninterpreted, in the derivation.
 @end deffn
 
 @noindent
@@ -5790,7 +5793,8 @@ information about monads.)
        [#:leaked-env-vars #f] @
        [#:script-name (string-append @var{name} "-builder")] @
        [#:deprecation-warnings #f] @
-       [#:local-build? #f] [#:substitutable? #t] [#:guile-for-build #f]
+       [#:local-build? #f] [#:substitutable? #t] @
+       [#:properties '()] [#:guile-for-build #f]
 Return a derivation @var{name} that runs @var{exp} (a gexp) with
 @var{guile-for-build} (a derivation) on @var{system}; @var{exp} is
 stored in a file called @var{script-name}.  When @var{target} is true,

guix/derivations.scm

@@ -80,6 +80,7 @@ (define-module (guix derivations)
             substitutable-derivation?
             substitution-oracle
             derivation-hash
+            derivation-properties
 
             read-derivation
             read-derivation-from-file
@@ -681,7 +682,8 @@ (define* (derivation store name builder args
                      references-graphs
                      allowed-references disallowed-references
                      leaked-env-vars local-build?
-                     (substitutable? #t))
+                     (substitutable? #t)
+                     (properties '()))
   "Build a derivation with the given arguments, and return the resulting
 <derivation> object.  When HASH and HASH-ALGO are given, a
 fixed-output derivation is created---i.e., one whose result is known in
@@ -708,7 +710,10 @@ (define* (derivation store name builder args
 derivations where the costs of data transfers would outweigh the benefits.
 
 When SUBSTITUTABLE? is false, declare that substitutes of the derivation's
-output should not be used."
+output should not be used.
+
+PROPERTIES must be an association list describing \"properties\" of the
+derivation.  It is kept as-is, uninterpreted, in the derivation."
   (define (add-output-paths drv)
     ;; Return DRV with an actual store path for each of its output and the
     ;; corresponding environment variable.
@@ -763,6 +768,10 @@ (define (user+system-env-vars)
                             `(("impureEnvVars"
                                . ,(string-join leaked-env-vars)))
                             '())
+                      ,@(match properties
+                          (() '())
+                          (lst `(("guix properties"
+                                  . ,(object->string properties)))))
                       ,@env-vars)))
       (match references-graphs
         (((file . path) ...)
@@ -851,6 +860,14 @@ (define (invalidate-derivation-caches!)
   (invalidate-memoization! derivation-path->base16-hash)
   (hash-clear! %derivation-cache))
 
+(define derivation-properties
+  (mlambdaq (drv)
+    "Return the property alist associated with DRV."
+    (match (assoc "guix properties"
+                  (derivation-builder-environment-vars drv))
+      ((_ . str) (call-with-input-string str read))
+      (#f        '()))))
+
 (define* (map-derivation store drv mapping
                          #:key (system (%current-system)))
   "Given MAPPING, a list of pairs of derivations, return a derivation based on
@@ -1129,7 +1146,8 @@ (define* (build-expression->derivation store name exp ;deprecated
                                        references-graphs
                                        allowed-references
                                        disallowed-references
-                                       local-build? (substitutable? #t))
+                                       local-build? (substitutable? #t)
+                                       (properties '()))
   "Return a derivation that executes Scheme expression EXP as a builder
 for derivation NAME.  INPUTS must be a list of (NAME DRV-PATH SUB-DRV)
 tuples; when SUB-DRV is omitted, \"out\" is assumed.  MODULES is a list
@@ -1149,7 +1167,8 @@ (define* (build-expression->derivation store name exp ;deprecated
 omitted or is #f, the value of the `%guile-for-build' fluid is used instead.
 
 See the `derivation' procedure for the meaning of REFERENCES-GRAPHS,
-ALLOWED-REFERENCES, DISALLOWED-REFERENCES, LOCAL-BUILD?, and SUBSTITUTABLE?."
+ALLOWED-REFERENCES, DISALLOWED-REFERENCES, LOCAL-BUILD?, SUBSTITUTABLE?,
+and PROPERTIES."
   (define guile-drv
     (or guile-for-build (%guile-for-build)))
 
@@ -1277,7 +1296,8 @@ (define %build-inputs
                 #:allowed-references allowed-references
                 #:disallowed-references disallowed-references
                 #:local-build? local-build?
-                #:substitutable? substitutable?)))
+                #:substitutable? substitutable?
+                #:properties properties)))
 
 
 ;;;

guix/gexp.scm

@@ -631,6 +631,7 @@ (define* (gexp->derivation name exp
                            allowed-references disallowed-references
                            leaked-env-vars
                            local-build? (substitutable? #t)
+                           (properties '())
 
                            ;; TODO: This parameter is transitional; it's here
                            ;; to avoid a full rebuild.  Remove it on the next
@@ -800,7 +801,8 @@ (define (extension-flags extension)
                       #:disallowed-references disallowed
                       #:leaked-env-vars leaked-env-vars
                       #:local-build? local-build?
-                      #:substitutable? substitutable?))))
+                      #:substitutable? substitutable?
+                      #:properties properties))))
 
 (define* (gexp-inputs exp #:key native?)
   "Return the input list for EXP.  When NATIVE? is true, return only native

tests/derivations.scm

@@ -1132,6 +1132,16 @@ (define (deps path . deps)
                                     ((p2 . _)
                                      (string<? p1 p2)))))))))))))
 
+(test-equal "derivation-properties"
+  (list '() '((type . test)))
+  (let ((drv1 (build-expression->derivation %store "bar"
+                                            '(mkdir %output)))
+        (drv2 (build-expression->derivation %store "foo"
+                                           '(mkdir %output)
+                                           #:properties '((type . test)))))
+    (list (derivation-properties drv1)
+          (derivation-properties drv2))))
+
 (test-equal "map-derivation"
   "hello"
   (let* ((joke (package-derivation %store guile-1.8))

tests/gexp.scm

@@ -476,7 +476,15 @@ (define guile ,guile)
     (return (and (string=? (readlink (string-append out "/foo")) guile)
                  (string=? (readlink out2) file)
                  (equal? refs (list (dirname (dirname guile))))
-                 (equal? refs2 (list file))))))
+                 (equal? refs2 (list file))
+                 (null? (derivation-properties drv))))))
+
+(test-assertm "gexp->derivation properties"
+  (mlet %store-monad ((drv (gexp->derivation "foo"
+                                             #~(mkdir #$output)
+                                             #:properties '((type . test)))))
+    (return (equal? '((type . test))
+                    (derivation-properties drv)))))
 
 (test-assertm "gexp->derivation vs. grafts"
   (mlet* %store-monad ((graft?  (set-grafting #f))