gnu: ocaml5: Add ocaml-mirage-xen.

* gnu/packages/ocaml5.scm (ocaml-mirage-xen): New variable.

Change-Id: Ib85099c8ccfab44e1e70ecaa056a25d48dd5191e
Signed-off-by: Julien Lepiller <julien@lepiller.eu>

CODEOWNERS

@@ -316,6 +316,7 @@ gnu/packages/librewolf\.scm                        @guix/mozilla
 gnu/packages/tor-browsers\.scm                     @guix/mozilla
 
 gnu/packages/ocaml\.scm                            @guix/ocaml
+gnu/packages/ocaml5\.scm                           @guix/ocaml
 gnu/packages/coq\.scm                              @guix/ocaml
 guix/build/ocaml-build-system\.scm                 @guix/ocaml
 guix/build/dune-build-system\.scm                  @guix/ocaml

etc/teams.scm

@@ -933,6 +933,7 @@ and Firefox."
 importer, and the ocaml-build-system."
         #:scope
         (list "gnu/packages/ocaml.scm"
+              "gnu/packages/ocaml5.scm"
               "gnu/packages/coq.scm"
               "guix/build/ocaml-build-system.scm"
               "guix/build/dune-build-system.scm"

gnu/local.mk

@@ -75,6 +75,7 @@
 # Copyright © 2025 Nigko Yerden <nigko.yerden@gmail.com>
 # Copyright © 2025 Cayetano Santos <csantosb@inventati.org>
 # Copyright © 2025 bdunahu <bdunahu@operationnull.com>
+# Copyright © 2025 Jason Conroy <jconroy@tscripta.net>
 #
 # This file is part of GNU Guix.
 #
@@ -518,6 +519,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/packages/nvi.scm				\
   %D%/packages/nx.scm				\
   %D%/packages/ocaml.scm			\
+  %D%/packages/ocaml5.scm			\
   %D%/packages/ocr.scm				\
   %D%/packages/openkinect.scm			\
   %D%/packages/onc-rpc.scm			\

gnu/packages/ocaml.scm

@@ -32,6 +32,7 @@
 ;;; Copyright © 2023 Arnaud DABY-SEESARAM <ds-ac@nanein.fr>
 ;;; Copyright © 2024 Sören Tempel <soeren@soeren-tempel.net>
 ;;; Copyright © 2025 Jussi Timperi <jussi.timperi@iki.fi>
+;;; Copyright © 2025 Jason Conroy <jconroy@tscripta.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -75,6 +76,7 @@
   #:use-module (gnu packages multiprecision)
   #:use-module (gnu packages ncurses)
   #:use-module (gnu packages node)
+  #:use-module ((gnu packages ocaml5) #:prefix ocaml5:)
   #:use-module (gnu packages parallel)
   #:use-module (gnu packages pcre)
   #:use-module (gnu packages perl)
@@ -222,89 +224,6 @@ OCaml and can effectively bootstrap OCaml 4.07.
 This package produces a native @command{ocamlc} and a bytecode @command{ocamllex}.")
       (license license:expat))))
 
-(define-public ocaml-5.0
-  (package
-    (name "ocaml")
-    (version "5.0.0")
-    (source (origin
-              (method git-fetch)
-              (uri (git-reference
-                    (url "https://github.com/ocaml/ocaml")
-                    (commit version)))
-              (file-name (git-file-name name version))
-              (sha256
-               (base32
-                "1p0p8wldrnbr61wfy3x4122017g4k5gjvfwlg3mvlqn8r2fxn2m5"))))
-    (build-system gnu-build-system)
-    (native-search-paths
-     (list (search-path-specification
-            (variable "OCAMLPATH")
-            (files (list "lib/ocaml" "lib/ocaml/site-lib")))
-           (search-path-specification
-            (variable "CAML_LD_LIBRARY_PATH")
-            (files (list "lib/ocaml/site-lib/stubslibs"
-                         "lib/ocaml/site-lib/stublibs")))))
-    (native-inputs
-     (list parallel perl pkg-config))
-    (inputs
-     (list libx11 libiberty ;needed for objdump support
-           zlib))                       ;also needed for objdump support
-    (arguments
-     `(#:configure-flags '("--enable-ocamltest")
-       #:test-target "tests"
-       ;; This doesn't have the desired effect and makes test runs less
-       ;; stable. See https://codeberg.org/guix/guix/pulls/2933.
-       #:parallel-tests? #f
-       #:make-flags '("defaultentry")
-       #:phases
-       (modify-phases %standard-phases
-         (add-after 'unpack 'enable-parallel-tests
-           (lambda _
-             ;; Patch the `tests` build target to enable a special parallel
-             ;; execution mode based on GNU Parallel.
-             (substitute* "Makefile"
-               (("-C testsuite all") "-C testsuite parallel"))))
-         (add-after 'unpack 'patch-/bin/sh-references
-           (lambda* (#:key inputs #:allow-other-keys)
-             (let* ((sh (search-input-file inputs "/bin/sh"))
-                    (quoted-sh (string-append "\"" sh "\"")))
-               (with-fluids ((%default-port-encoding #f))
-                 (for-each
-                  (lambda (file)
-                    (substitute* file
-                      (("\"/bin/sh\"")
-                       (begin
-                         (format (current-error-port) "\
-patch-/bin/sh-references: ~a: changing `\"/bin/sh\"' to `~a'~%"
-                                 file quoted-sh)
-                         quoted-sh))))
-                  (find-files "." "\\.ml$")))))))))
-    (home-page "https://ocaml.org/")
-    (synopsis "The OCaml programming language")
-    (description
-     "OCaml is a general purpose industrial-strength programming language with
-an emphasis on expressiveness and safety.  Developed for more than 20 years at
-Inria it benefits from one of the most advanced type systems and supports
-functional, imperative and object-oriented styles of programming.")
-    ;; The compiler is distributed under qpl1.0 with a change to choice of
-    ;; law: the license is governed by the laws of France.  The library is
-    ;; distributed under lgpl2.0.
-    (license (list license:qpl license:lgpl2.0))))
-
-(define-public ocaml-5.3
-  (package
-    (inherit ocaml-5.0)
-    (version "5.3.0")
-    (source (origin
-              (method git-fetch)
-              (uri (git-reference
-                    (url "https://github.com/ocaml/ocaml")
-                    (commit version)))
-              (file-name (git-file-name "ocaml" version))
-              (sha256
-               (base32
-                "05jhy9zn53v12rn3sg3vllqf5blv1gp7f06803npimc58crxy6rv"))))))
-
 (define-public ocaml-4.14
   (package
     (name "ocaml")
@@ -1679,13 +1598,6 @@ compilers that can directly deal with packages.")
     (native-inputs
      (list m4 ocaml-4.09))))
 
-(define-public ocaml5.0-findlib
-  (package
-    (inherit ocaml-findlib)
-    (name "ocaml5.0-findlib")
-    (native-inputs
-     (list m4 ocaml-5.0))))
-
 (define-public ocaml-ounit2
   (package
     (name "ocaml-ounit2")
@@ -2017,9 +1929,6 @@ Descriptions of projects, libraries and executables are provided in
 (define-public ocaml4.09-dune-bootstrap
   (package-with-ocaml4.09 dune-bootstrap))
 
-(define-public ocaml5.0-dune-bootstrap
-  (package-with-ocaml5.0 dune-bootstrap))
-
 (define-public dune-configurator
   (package
     (inherit dune-bootstrap)
@@ -2041,7 +1950,8 @@ Descriptions of projects, libraries and executables are provided in
     (propagated-inputs
      (list ocaml-csexp))
     (properties `((ocaml4.09-variant . ,(delay ocaml4.09-dune-configurator))
-                  (ocaml5.0-variant . ,(delay ocaml5.0-dune-configurator))))
+                  (ocaml5.0-variant . ,(delay ocaml5.0-dune-configurator))
+                  (ocaml5.3-variant . ,(delay ocaml5:ocaml5.3-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
@@ -2072,9 +1982,9 @@ config.h files for instance.  Among other things, dune-configurator allows one t
     (name "ocaml5.0-dune-configurator")
     (arguments
      `(,@(package-arguments dune-configurator)
-       #:dune ,ocaml5.0-dune-bootstrap
-       #:ocaml ,ocaml-5.0
-       #:findlib ,ocaml5.0-findlib))
+       #:dune ,ocaml5:ocaml5.0-dune-bootstrap
+       #:ocaml ,ocaml5:ocaml-5.0
+       #:findlib ,ocaml5:ocaml5.0-findlib))
     (propagated-inputs (list ocaml5.0-csexp))))
 
 (define-public dune
@@ -2084,7 +1994,8 @@ config.h files for instance.  Among other things, dune-configurator allows one t
      (list dune-configurator))
     (properties `((ocaml4.07-variant . ,(delay ocaml4.07-dune))
                   (ocaml4.09-variant . ,(delay ocaml4.09-dune))
-                  (ocaml5.0-variant . ,(delay ocaml5.0-dune))))))
+                  (ocaml5.0-variant . ,(delay ocaml5.0-dune))
+                  (ocaml5.3-variant . ,(delay ocaml5:ocaml5.3-dune))))))
 
 (define-public ocaml4.09-dune
   (package
@@ -2108,7 +2019,7 @@ config.h files for instance.  Among other things, dune-configurator allows one t
 
 (define-public ocaml5.0-dune
   (package
-    (inherit ocaml5.0-dune-bootstrap)
+    (inherit ocaml5:ocaml5.0-dune-bootstrap)
     (propagated-inputs
      (list ocaml5.0-dune-configurator))))
 
@@ -2237,7 +2148,8 @@ executables and libraries")))
     (propagated-inputs
      (list ocaml-result))
     (properties `((ocaml4.09-variant . ,(delay ocaml4.09-csexp))
-                  (ocaml5.0-variant . ,(delay ocaml5.0-csexp))))
+                  (ocaml5.0-variant . ,(delay ocaml5.0-csexp))
+                  (ocaml5.3-variant . ,(delay ocaml5:ocaml5.3-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
@@ -2271,10 +2183,10 @@ module of this library is parameterised by the type of S-expressions.")
     (inherit ocaml-csexp)
     (name "ocaml5.0-csexp")
     (arguments
-     `(#:ocaml ,ocaml-5.0
-       #:findlib ,ocaml5.0-findlib
+     `(#:ocaml ,ocaml5:ocaml-5.0
+       #:findlib ,ocaml5:ocaml5.0-findlib
        ,@(substitute-keyword-arguments (package-arguments ocaml-csexp)
-           ((#:dune _) ocaml5.0-dune-bootstrap))))
+           ((#:dune _) ocaml5:ocaml5.0-dune-bootstrap))))
     (propagated-inputs
      `(("ocaml-result" ,ocaml5.0-result)))))
 
@@ -2397,7 +2309,8 @@ bitsrings in Erlang style as primitives to the language.")))
     (arguments
      `(#:dune ,dune-bootstrap))
     (properties `((ocaml4.09-variant . ,(delay ocaml4.09-result))
-                  (ocaml5.0-variant . ,(delay ocaml5.0-result))))
+                  (ocaml5.0-variant . ,(delay ocaml5.0-result))
+                  (ocaml5.3-variant . ,(delay ocaml5:ocaml5.3-result))))
     (home-page "https://github.com/janestreet/result")
     (synopsis "Compatibility Result module")
     (description "Uses the new result type defined in OCaml >= 4.03 while
@@ -2419,9 +2332,9 @@ defined in this library.")
     (inherit ocaml-result)
     (name "ocaml5.0-result")
     (arguments
-     `(#:dune ,ocaml5.0-dune-bootstrap
-       #:ocaml ,ocaml-5.0
-       #:findlib ,ocaml5.0-findlib))))
+     `(#:dune ,ocaml5:ocaml5.0-dune-bootstrap
+       #:ocaml ,ocaml5:ocaml-5.0
+       #:findlib ,ocaml5:ocaml5.0-findlib))))
 
 (define-public ocaml-iso8601
   (package

guix/build-system/dune.scm

@@ -3,6 +3,7 @@
 ;;; Copyright © 2017 Ben Woodcroft <donttrustben@gmail.com>
 ;;; Copyright © 2021, 2022 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2021 pukkamustard <pukkamustard@posteo.net>
+;;; Copyright © 2025 Jason Conroy <jconroy@tscripta.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -31,12 +32,22 @@
   #:use-module (srfi srfi-1)
   #:export (%dune-build-system-modules
             dune-build
-            dune-build-system))
+            dune-build-system
+            ocaml5-dune-build-system))
 
 ;; Commentary:
 ;;
-;; Standard build procedure for packages using dune. This is implemented as an
-;; extension of `ocaml-build-system'.
+;; Standard build procedures for packages using dune. These are implemented as
+;; extensions of `ocaml-build-system'.
+;;
+;; Multiple instances of the build system exist to support different versions
+;; of the OCaml compiler and its associated tools. Choose `dune-build-system`
+;; for a build system that works with Guix's default version of the compiler,
+;; or choose `ocamlX-dune-build-system` for some other compiler version X.
+;;
+;; Adaptor functions of the form `package-with-ocamlX.Y` defined in the OCaml
+;; build system will also work on packages with the Dune build system, subject
+;; to the same caveats.
 ;;
 ;; Code:
 
@@ -45,54 +56,49 @@
   `((guix build dune-build-system)
     ,@ocaml:%ocaml-build-system-modules))
 
-(define (default-dune)
-  "Return the default OCaml package."
+(define (make-lower default-ocaml default-findlib default-dune)
+  (lambda* (name
+            #:key source inputs native-inputs outputs system target
+            (dune (default-dune))
+            (ocaml (default-ocaml))
+            (findlib (default-findlib))
+            #:allow-other-keys
+            #:rest arguments)
+    "Return a bag for NAME."
 
-  ;; Do not use `@' to avoid introducing circular dependencies.
-  (let ((module (resolve-interface '(gnu packages ocaml))))
-    (module-ref module 'dune)))
+    ;; Flags that put dune into reproducible build mode.
+    (define dune-release-flags
+      (if (version>=? (package-version dune) "2.5.0")
+          ;; For dune >= 2.5.0 this is just --release.
+          ''("--release")
+          ;; --release does not exist before 2.5.0.  Replace with flags compatible
+          ;; with our old ocaml4.07-dune (1.11.3)
+          ''("--root" "." "--ignore-promoted-rules" "--no-config"
+             "--profile" "release")))
 
-(define* (lower name
-                #:key source inputs native-inputs outputs system target
-                (dune (default-dune))
-                (ocaml (ocaml:default-ocaml))
-                (findlib (ocaml:default-findlib))
-                #:allow-other-keys
-                #:rest arguments)
-  "Return a bag for NAME."
+    (define private-keywords
+      '(#:target #:dune #:findlib #:ocaml #:inputs #:native-inputs))
 
-  ;; Flags that put dune into reproducible build mode.
-  (define dune-release-flags
-    (if (version>=? (package-version dune) "2.5.0")
-        ;; For dune >= 2.5.0 this is just --release.
-        ''("--release")
-        ;; --release does not exist before 2.5.0.  Replace with flags compatible
-        ;; with our old ocaml4.07-dune (1.11.3)
-        ''("--root" "." "--ignore-promoted-rules" "--no-config"
-           "--profile" "release")))
-
-  (define private-keywords
-    '(#:target #:dune #:findlib #:ocaml #:inputs #:native-inputs))
-
-  (and (not target)                               ;XXX: no cross-compilation
-       (let ((base (ocaml:lower name
-                                #:source source
-                                #:inputs inputs
-                                #:native-inputs native-inputs
-                                #:outputs outputs
-                                #:system system
-                                #:target target
-                                #:ocaml ocaml
-                                #:findlib findlib
-                                arguments)))
-         (bag
-           (inherit base)
-           (build-inputs `(("dune" ,dune)
-                           ,@(bag-build-inputs base)))
-           (build dune-build)
-           (arguments (append
-                       `(#:dune-release-flags ,dune-release-flags)
-                       (strip-keyword-arguments private-keywords arguments)))))))
+    (and (not target)                   ;XXX: no cross-compilation
+         (let ((base ((ocaml:make-lower default-ocaml default-findlib)
+                      name
+                      #:source source
+                      #:inputs inputs
+                      #:native-inputs native-inputs
+                      #:outputs outputs
+                      #:system system
+                      #:target target
+                      #:ocaml ocaml
+                      #:findlib findlib
+                      arguments)))
+           (bag
+             (inherit base)
+             (build-inputs `(("dune" ,dune)
+                             ,@(bag-build-inputs base)))
+             (build dune-build)
+             (arguments (append
+                         `(#:dune-release-flags ,dune-release-flags)
+                         (strip-keyword-arguments private-keywords arguments))))))))
 
 (define* (dune-build name inputs
                      #:key
@@ -158,10 +164,26 @@ provides a 'setup.ml' file as its build system."
                     #:graft? #f
                     #:guile-for-build guile))
 
-(define dune-build-system
+(define (make-dune-build-system default-ocaml
+                                default-findlib
+                                default-dune)
   (build-system
     (name 'dune)
     (description "The standard Dune build system")
-    (lower lower)))
+    (lower (make-lower default-ocaml
+                       default-findlib
+                       default-dune))))
+
+(define dune-build-system
+  ;; The default instance of the build system, using Guix's default OCaml
+  ;; compiler version.
+  (make-dune-build-system ocaml:default-ocaml
+                          ocaml:default-findlib
+                          ocaml:default-dune))
+
+(define ocaml5-dune-build-system
+  (make-dune-build-system ocaml:default-ocaml5
+                          ocaml:default-ocaml5-findlib
+                          ocaml:default-ocaml5-dune))
 
 ;;; dune.scm ends here

guix/build-system/ocaml.scm

@@ -2,6 +2,7 @@
 ;;; Copyright © 2016, 2017, 2018 Julien Lepiller <julien@lepiller.eu>
 ;;; Copyright © 2017 Ben Woodcroft <donttrustben@gmail.com>
 ;;; Copyright © 2021-2022 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2025 Jason Conroy <jconroy@tscripta.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -33,32 +34,51 @@
             strip-ocaml4.09-variant
             package-with-ocaml5.0
             strip-ocaml5.0-variant
+            package-with-ocaml5.3
+            strip-ocaml5.3-variant
             default-findlib
             default-ocaml
-            lower
+            default-dune
+            default-ocaml5-findlib
+            default-ocaml5
+            default-ocaml5-dune
+            make-lower
             ocaml-build
-            ocaml-build-system))
+            ocaml-build-system
+            ocaml5-build-system))
 
 ;; Commentary:
 ;;
-;; Standard build procedure for packages using ocaml. This is implemented as an
-;; extension of `gnu-build-system'.
+;; Standard build procedures for packages using ocaml. These are implemented
+;; as extensions of `gnu-build-system'.
 ;;
-;; OCaml packages don't use a single standard for their build system. Some use
-;; autotools, other use custom configure scripts with Makefiles, others use
-;; oasis to generate the configure script and Makefile and lastly, some use
-;; custom ocaml scripts.
+;; OCaml packages don't use a single standard for their build
+;; system. Historically, some use autotools, other use custom configure
+;; scripts with Makefiles, others use oasis to generate the configure script
+;; and Makefile, and some use custom ocaml scripts. The majority of new
+;; packages instead use Dune, which has a separate `dune-build-system`.
 ;;
-;; Each phase in the build system will try to figure out what the build system
-;; is for that package. Most packages come with a custom configure script and
-;; a Makefile that in turn call custom build tools. Packages built with oasis
-;; will have a `setup.ml' file in the top directory, that can be used for all
-;; phases. In that case the Makefile is here only to call that script. In case
-;; the setup.ml do not work as expected, the @var{use-make} argument can be
-;; used to ignore the setup.ml file and run make instead.
+;; Each phase in this build system will try to figure out which of the
+;; approaches above is used for the package. Most packages come with a custom
+;; configure script and a Makefile that in turn call custom build
+;; tools. Packages built with oasis will have a `setup.ml' file in the top
+;; directory, that can be used for all phases. In that case the Makefile is
+;; here only to call that script. In case the setup.ml do not work as
+;; expected, the @var{use-make} argument can be used to ignore the setup.ml
+;; file and run make instead. Some packages use their own custom scripts
+;; (e.g., `pkg/pkg.ml' or `pkg/build.ml') which can be used here too.
 ;;
-;; Some packages use their own custom scripts, `pkg/pkg.ml' or
-;; `pkg/build.ml'. They can be used here too.
+;; Multiple instances of the build system exist to support different versions
+;; of the OCaml compiler and its associated tools. Choose `ocaml-build-system`
+;; for a build system that works with Guix's default version of the compiler,
+;; or choose `ocamlX-build-system` for some other compiler version X.
+;;
+;; Adaptor functions of the form `package-with-ocamlX.Y` transform a package
+;; to use a different compiler version for its own build and for those of all
+;; transitive dependencies. These adaptors exist for user convenience, but a
+;; package shipped with the distribution should generally use the
+;; `build-system` field instead to identify the version of the OCaml stack
+;; that it supports.
 ;;
 ;; Code:
 
@@ -75,6 +95,10 @@
   "Return the default OCaml-findlib package, resolved lazily."
   (@* (gnu packages ocaml) ocaml-findlib))
 
+(define (default-dune)
+  "Return the default Dune package, resolved lazily."
+  (@* (gnu packages ocaml) dune))
+
 (define (default-dune-build-system)
   "Return the dune-build-system, resolved lazily."
   (@* (guix build-system dune) dune-build-system))
@@ -98,14 +122,31 @@
   (@* (gnu packages ocaml) ocaml4.09-dune))
 
 (define (default-ocaml5.0)
-  (@* (gnu packages ocaml) ocaml-5.0))
+  (@* (gnu packages ocaml5) ocaml-5.0))
 
 (define (default-ocaml5.0-findlib)
-  (@* (gnu packages ocaml) ocaml5.0-findlib))
+  (@* (gnu packages ocaml5) ocaml5.0-findlib))
 
 (define (default-ocaml5.0-dune)
   (@* (gnu packages ocaml) ocaml5.0-dune))
 
+(define (default-ocaml5.3)
+  (@* (gnu packages ocaml5) ocaml-5.3))
+
+(define (default-ocaml5.3-findlib)
+  (@* (gnu packages ocaml5) ocaml5.3-findlib))
+
+(define (default-ocaml5.3-dune)
+  (@* (gnu packages ocaml5) ocaml5.3-dune))
+
+;; The default versions of core packages within the 5.x series.
+
+(define default-ocaml5 default-ocaml5.3)
+
+(define default-ocaml5-findlib default-ocaml5.3-findlib)
+
+(define default-ocaml5-dune default-ocaml5.3-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
@@ -130,6 +171,12 @@ pre-defined variants."
                     variant-property))
         (const #f)))
 
+  (define (has-ocaml-build-system? p)
+    (eq? 'ocaml (build-system-name (package-build-system p))))
+
+  (define (has-dune-build-system? p)
+    (eq? 'dune (build-system-name (package-build-system p))))
+
   (define (transform p)
     (cond
      ;; If VARIANT-PROPERTY is present, use that.
@@ -137,8 +184,7 @@ pre-defined variants."
       => force)
 
      ;; Otherwise build the new package object graph.
-     ((or (eq? (package-build-system p) ocaml-build-system)
-          (eq? (package-build-system p) (default-dune-build-system)))
+     ((or (has-ocaml-build-system? p) (has-dune-build-system? p))
       (package
         (inherit p)
         (location (package-location p))
@@ -155,15 +201,13 @@ pre-defined variants."
            (ensure-keyword-arguments (package-arguments p)
                                      `(#:ocaml   ,ocaml
                                        #:findlib ,findlib
-                                       ,@(if (eq? (package-build-system p)
-                                                  (default-dune-build-system))
+                                       ,@(if (has-dune-build-system? p)
                                              `(#:dune ,dune)
                                              '())))))))
      (else p)))
 
   (define (cut? p)
-    (or (not (or (eq? (package-build-system p) ocaml-build-system)
-                 (eq? (package-build-system p) (default-dune-build-system))))
+    (or (not (or (has-ocaml-build-system? p) (has-dune-build-system? p)))
         (package-variant p)))
 
   (package-mapping transform cut?))
@@ -207,33 +251,47 @@ pre-defined variants."
     (inherit p)
     (properties (alist-delete 'ocaml5.0-variant (package-properties p)))))
 
-(define* (lower name
-                #:key source inputs native-inputs outputs system target
-                (ocaml (default-ocaml))
-                (findlib (default-findlib))
-                #:allow-other-keys
-                #:rest arguments)
-  "Return a bag for NAME."
-  (define private-keywords
-    '(#:target #:ocaml #:findlib #:inputs #:native-inputs))
+(define package-with-ocaml5.3
+  (package-with-explicit-ocaml (delay (default-ocaml5.3))
+                               (delay (default-ocaml5.3-findlib))
+                               (delay (default-ocaml5.3-dune))
+                               "ocaml-" "ocaml5.3-"
+                               #:variant-property 'ocaml5.3-variant))
 
-  (and (not target)                               ;XXX: no cross-compilation
-       (bag
-         (name name)
-         (system system)
-         (host-inputs `(,@(if source
-                              `(("source" ,source))
-                              '())
-                        ,@inputs))
-         (build-inputs `(("ocaml" ,ocaml)
-                         ("findlib" ,findlib)
-                         ,@native-inputs
+(define (strip-ocaml5.3-variant p)
+  "Remove the 'ocaml5.3-variant' property from P."
+  (package
+    (inherit p)
+    (properties (alist-delete 'ocaml5.3-variant (package-properties p)))))
 
-                         ;; Keep the standard inputs of 'gnu-build-system'.
-                         ,@(standard-packages)))
-         (outputs outputs)
-         (build ocaml-build)
-         (arguments (strip-keyword-arguments private-keywords arguments)))))
+(define (make-lower default-ocaml default-findlib)
+  (lambda* (name
+            #:key source inputs native-inputs outputs system target
+            (ocaml (default-ocaml))
+            (findlib (default-findlib))
+            #:allow-other-keys
+            #:rest arguments)
+    "Return a bag for NAME."
+    (define private-keywords
+      '(#:target #:ocaml #:findlib #:inputs #:native-inputs))
+
+    (and (not target)                   ;XXX: no cross-compilation
+         (bag
+           (name name)
+           (system system)
+           (host-inputs `(,@(if source
+                                `(("source" ,source))
+                                '())
+                          ,@inputs))
+           (build-inputs `(("ocaml" ,ocaml)
+                           ("findlib" ,findlib)
+                           ,@native-inputs
+
+                           ;; Keep the standard inputs of 'gnu-build-system'.
+                           ,@(standard-packages)))
+           (outputs outputs)
+           (build ocaml-build)
+           (arguments (strip-keyword-arguments private-keywords arguments))))))
 
 (define* (ocaml-build name inputs
                       #:key
@@ -293,10 +351,19 @@ provides a 'setup.ml' file as its build system."
                     #:graft? #f
                     #:guile-for-build guile))
 
-(define ocaml-build-system
+(define (make-ocaml-build-system default-ocaml default-findlib)
   (build-system
     (name 'ocaml)
     (description "The standard OCaml build system")
-    (lower lower)))
+    (lower (make-lower default-ocaml default-findlib))))
+
+(define ocaml-build-system
+  ;; The default instance of the build system, using Guix's default OCaml
+  ;; compiler version.
+  (make-ocaml-build-system default-ocaml default-findlib))
+
+(define ocaml5-build-system
+  (make-ocaml-build-system default-ocaml5 default-ocaml5-findlib))
+
 
 ;;; ocaml.scm ends here

guix/build/ocaml-build-system.scm

@@ -89,13 +89,25 @@
                   #:allow-other-keys)
   "Install the given package."
   (let ((out (assoc-ref outputs "out")))
-    (if (and (file-exists? "setup.ml") (not use-make?))
+    (cond
+     ((and (file-exists? "setup.ml") (not use-make?))
       (apply invoke "ocaml" "setup.ml"
-             (string-append "-" install-target) build-flags)
-      (if (file-exists? "Makefile")
-        (apply invoke "make" install-target make-flags)
-        (invoke "opam-installer" "-i" (string-append "--prefix=" out)
-                (string-append "--libdir=" out "/lib/ocaml/site-lib")))))
+             (string-append "-" install-target) build-flags))
+     ((file-exists? "Makefile")
+      (apply invoke "make" install-target make-flags))
+     ;; Use either opam-installer or opaline, which both understand
+     ;; opam's `.install` file format.  opam-installer is the standard
+     ;; platform tool, while opaline is a fallback for packages with
+     ;; circular dependencies involving opam.
+     ;; (https://codeberg.org/guix/guix/issues/3588)
+     ((which "opam-installer")
+      (invoke "opam-installer" "-i" (string-append "--prefix=" out)
+              (string-append "--libdir=" out "/lib/ocaml/site-lib")))
+     ((which "opaline")
+      (invoke "opaline" "-prefix" out
+              "-libdir" (string-append out "/lib/ocaml/site-lib")))
+     (else (error (string-append "Either 'opam-installer' or 'opaline' "
+                                 "must exist in $PATH at build time.")))))
   #t)
 
 (define* (prepare-install #:key outputs #:allow-other-keys)