guix: ocaml: Add package-with-ocaml4.09.

* guix/build-system/ocaml.scm (package-with-ocaml4.09)
(strip-ocaml4.09-variant): New variables.
* gnu/packages/ocaml.scm (ocaml4.09-result, ocaml4.09-csexp)
(ocaml4.09-dune-configurator, ocaml4.09-dune): New variables.

gnu/packages/ocaml.scm

@@ -1315,6 +1315,9 @@ release of Jane Street packages.  It reads metadata from @file{dune} files
 following a very simple s-expression syntax.")
     (license license:expat)))
 
+(define ocaml4.09-dune-bootstrap
+  (package-with-ocaml4.09 dune-bootstrap))
+
 (define-public dune-configurator
   (package
     (inherit dune-bootstrap)
@@ -1327,6 +1330,7 @@ following a very simple s-expression syntax.")
        #:tests? #f))
     (propagated-inputs
      `(("ocaml-csexp" ,ocaml-csexp)))
+    (properties `((ocaml4.09-variant . ,(delay ocaml4.09-dune-configurator))))
     (synopsis "Dune helper library for gathering system configuration")
     (description "Dune-configurator is a small library that helps writing
 OCaml scripts that test features available on the system, in order to generate
@@ -1339,12 +1343,32 @@ config.h files for instance.  Among other things, dune-configurator allows one t
 @item generate config.h file
 @end itemize")))
 
+(define-public ocaml4.09-dune-configurator
+  (package
+    (inherit dune-configurator)
+    (name "ocaml4.09-dune-configurator")
+    (arguments
+     `(#:package "dune-configurator"
+       #:tests? #f
+       #:dune ,ocaml4.09-dune-bootstrap
+       #:ocaml ,ocaml-4.09
+       #:findlib ,ocaml4.09-findlib))
+    (propagated-inputs
+     `(("ocaml-csexp" ,ocaml4.09-csexp)))))
+
 (define-public dune
   (package
     (inherit dune-bootstrap)
     (propagated-inputs
      `(("dune-configurator" ,dune-configurator)))
-    (properties `((ocaml4.07-variant . ,(delay ocaml4.07-dune))))))
+    (properties `((ocaml4.07-variant . ,(delay ocaml4.07-dune))
+                  (ocaml4.09-variant . ,(delay ocaml4.09-dune))))))
+
+(define-public ocaml4.09-dune
+  (package
+    (inherit ocaml4.09-dune-bootstrap)
+    (propagated-inputs
+     `(("dune-configurator" ,dune-configurator)))))
 
 (define-public ocaml4.07-dune
   (package
@@ -1385,6 +1409,7 @@ config.h files for instance.  Among other things, dune-configurator allows one t
              #t)))))
     (propagated-inputs
      `(("ocaml-result" ,ocaml-result)))
+    (properties `((ocaml4.09-variant . ,(delay ocaml4.09-csexp))))
     (home-page "https://github.com/ocaml-dune/csexp")
     (synopsis "Parsing and printing of S-expressions in Canonical form")
     (description "This library provides minimal support for Canonical
@@ -1401,6 +1426,18 @@ To avoid a dependency on a particular S-expression library, the only
 module of this library is parameterised by the type of S-expressions.")
     (license license:expat)))
 
+(define-public ocaml4.09-csexp
+  (package
+    (inherit ocaml-csexp)
+    (name "ocaml4.09-csexp")
+    (arguments
+     `(#:ocaml ,ocaml-4.09
+       #:findlib ,ocaml4.09-findlib
+       ,@(substitute-keyword-arguments (package-arguments ocaml-csexp)
+           ((#:dune _) ocaml4.09-dune-bootstrap))))
+    (propagated-inputs
+     `(("ocaml-result" ,ocaml4.09-result)))))
+
 (define-public ocaml-migrate-parsetree
   (package
     (name "ocaml-migrate-parsetree")
@@ -1509,6 +1546,7 @@ powerful.")
     (arguments
      `(#:test-target "."
        #:dune ,dune-bootstrap))
+    (properties `((ocaml4.09-variant . ,(delay ocaml4.09-result))))
     (home-page "https://github.com/janestreet/result")
     (synopsis "Compatibility Result module")
     (description "Uses the new result type defined in OCaml >= 4.03 while
@@ -1516,6 +1554,16 @@ staying compatible with older version of OCaml should use the Result module
 defined in this library.")
     (license license:bsd-3)))
 
+(define-public ocaml4.09-result
+  (package
+    (inherit ocaml-result)
+    (name "ocaml4.09-result")
+    (arguments
+     `(#:test-target "."
+       #:dune ,ocaml4.09-dune-bootstrap
+       #:ocaml ,ocaml-4.09
+       #:findlib ,ocaml4.09-findlib))))
+ 
 (define-public ocaml-topkg
   (package
     (name "ocaml-topkg")

guix/build-system/ocaml.scm

@@ -29,6 +29,8 @@
   #:export (%ocaml-build-system-modules
             package-with-ocaml4.07
             strip-ocaml4.07-variant
+            package-with-ocaml4.09
+            strip-ocaml4.09-variant
             default-findlib
             default-ocaml
             lower
@@ -96,6 +98,18 @@
   (let ((module (resolve-interface '(gnu packages ocaml))))
     (module-ref module 'ocaml4.07-dune)))
 
+(define (default-ocaml4.09)
+  (let ((ocaml (resolve-interface '(gnu packages ocaml))))
+    (module-ref ocaml 'ocaml-4.09)))
+
+(define (default-ocaml4.09-findlib)
+  (let ((module (resolve-interface '(gnu packages ocaml))))
+    (module-ref module 'ocaml4.09-findlib)))
+
+(define (default-ocaml4.09-dune)
+  (let ((module (resolve-interface '(gnu packages ocaml))))
+    (module-ref module 'ocaml4.09-dune)))
+
 (define* (package-with-explicit-ocaml ocaml findlib dune old-prefix new-prefix
                                        #:key variant-property)
   "Return a procedure of one argument, P.  The procedure creates a package
@@ -171,6 +185,19 @@ pre-defined variants."
     (inherit p)
     (properties (alist-delete 'ocaml4.07-variant (package-properties p)))))
 
+(define package-with-ocaml4.09
+  (package-with-explicit-ocaml (delay (default-ocaml4.09))
+                               (delay (default-ocaml4.09-findlib))
+                               (delay (default-ocaml4.09-dune))
+                               "ocaml-" "ocaml4.09-"
+                               #:variant-property 'ocaml4.09-variant))
+
+(define (strip-ocaml4.09-variant p)
+  "Remove the 'ocaml4.09-variant' property from P."
+  (package
+    (inherit p)
+    (properties (alist-delete 'ocaml4.09-variant (package-properties p)))))
+
 (define* (lower name
                 #:key source inputs native-inputs outputs system target
                 (ocaml (default-ocaml))