gnu: Add ocaml-js-build-tools.

* gnu/packages/ocaml.scm (ocaml-js-build-tools): New variable.

gnu/packages/ocaml.scm

@@ -66,6 +66,46 @@ (define (ocaml-forge-uri name version file-number)
                  (number->string file-number) "/" name "-" version
                  ".tar.gz"))
 
+;; Janestreet packages are found in a similar way and all need the same patch.
+(define (janestreet-origin name version hash)
+  (origin (method url-fetch)
+          (uri (string-append "https://ocaml.janestreet.com/ocaml-core/"
+                              (version-major+minor version) "/files/"
+                              name "-" version ".tar.gz"))
+          (sha256 (base32 hash))
+          (modules '((guix build utils)))
+          (snippet
+           (let ((pattern (string-append "lib/" name)))
+             `(begin
+                ;; install.ml contains an invalid reference to the ppx file and
+                ;; propagates this error to the generated META file.  It
+                ;; looks for it in the "lib" directory, but it is installed in
+                ;; "lib/ocaml/site-lib/package".  This substitute does not change
+                ;; this file for non ppx packages.
+                (substitute* "install.ml"
+                  ((,pattern) (string-append "lib/ocaml/site-lib/" ,name)))
+                ;; The standard Makefile would try to install janestreet modules
+                ;; in OCaml's directory in the store, which is read-only.
+                (substitute* "Makefile"
+                  (("--prefix")
+                   "--libdir $(LIBDIR) --prefix")))))))
+
+;; They also require almost the same set of arguments
+(define janestreet-arguments
+  `(#:use-make? #t
+    #:make-flags
+    (list (string-append "CONFIGUREFLAGS=--prefix "
+                         (assoc-ref %outputs "out")
+                         " --enable-tests")
+          (string-append "LIBDIR="
+                         (assoc-ref %outputs "out")
+                         "/lib/ocaml/site-lib")
+          ;; for ocaml-bin-prot, otherwise ignored
+          (string-append "OCAML_TOPLEVEL_PATH="
+                         (assoc-ref %build-inputs "findlib")
+                         "/lib/ocaml/site-lib"))
+    #:phases (modify-phases %standard-phases (delete 'configure))))
+
 (define-public ocaml
   (package
     (name "ocaml")
@@ -1942,3 +1982,25 @@ (define-public ocaml-oasis
 system in your OCaml projects.  It helps to create standard entry points in your
 build system and allows external tools to analyse your project easily.")
     (license license:lgpl2.1+))) ; with ocaml static compilation exception
+
+(define-public ocaml-js-build-tools
+  (package
+    (name "ocaml-js-build-tools")
+    (version "113.33.06")
+    (source (janestreet-origin "js-build-tools" version
+              "0r8z4fz8iy5y6hkdlkpwf6rk4qigcr3dzyv35585xgg2ahf12zy6"))
+    (native-inputs
+     `(("oasis" ,ocaml-oasis)
+       ("opam" ,opam)))
+    (build-system ocaml-build-system)
+    (arguments janestreet-arguments)
+    (home-page "https://github.com/janestreet/js-build-tools")
+    (synopsis "Collection of tools to help building Jane Street Packages")
+    (description "This package contains tools to help building Jane Street
+packages, but can be used for other purposes.  It contains:
+@enumerate
+@item an @command{oasis2opam-install} tool to produce a @file{.install} file
+from the oasis build log
+@item a @code{js_build_tools} ocamlbuild plugin with various goodies.
+@end enumerate")
+    (license license:asl2.0)))