Use dune-build-info

lib/Version.ml

@@ -0,0 +1,14 @@
+(**********************************************************************
+ *                                                                    *
+ *                            OCamlFormat                             *
+ *                                                                    *
+ *  Copyright (c) 2017-present, Facebook, Inc.  All rights reserved.  *
+ *                                                                    *
+ *  This source code is licensed under the MIT license found in the   *
+ *  LICENSE file in the root directory of this source tree.           *
+ *                                                                    *
+ **********************************************************************)
+
+let version =
+  let open Build_info.V1 in
+  version () |> Option.value_map ~f:Version.to_string ~default:"unknown"

lib/Version.mli

@@ -0,0 +1,22 @@
+(**********************************************************************
+ *                                                                    *
+ *                            OCamlFormat                             *
+ *                                                                    *
+ *  Copyright (c) 2017-present, Facebook, Inc.  All rights reserved.  *
+ *                                                                    *
+ *  This source code is licensed under the MIT license found in the   *
+ *  LICENSE file in the root directory of this source tree.           *
+ *                                                                    *
+ **********************************************************************)
+
+val version : string
+(** A version number, or "unknown". This is provided by [dune-build-info],
+    which means that it will be resolved in the following way:
+
+    - if (version) is set in (dune-project), it is used. This is what happens
+      when using opam pins (through dune subst), or for released versions
+      (through dune-release).
+    - otherwise, a description from [git describe] will be used. Caveat for
+      this case: binaries under [_build/] will not have this information, but
+      [dune install --prefix _install] will copy a valid binary under
+      [_install/bin]. *)

lib/dune

@@ -9,13 +9,6 @@
 ;                                                                        ;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-(rule
- (targets Version.ml)
- (deps (universe))
- (action
-  (run ocaml %{dep:../tools/gen_version.mlt} Version.ml))
- (mode fallback))
-
 (rule
  (copy# compat/%{read:compat-file} compat.ml))
 
@@ -32,4 +25,4 @@
   (:standard -open Import))
  ;;INSERT_BISECT_HERE;;
  (libraries format_ import ocaml-migrate-parsetree odoc.model odoc.parser
-   parse_wyc re uuseg uuseg.string))
+   parse_wyc re uuseg uuseg.string dune-build-info))

ocamlformat.opam

@@ -17,7 +17,7 @@ bug-reports: "https://github.com/ocaml-ppx/ocamlformat/issues"
 dev-repo: "git+https://github.com/ocaml-ppx/ocamlformat.git"
 license: "MIT"
 build: [
-  ["ocaml" "tools/gen_version.mlt" "lib/Version.ml" version] {pinned}
+  ["dune" "subst"] {pinned}
   ["dune" "build" "-p" name "-j" jobs]
   ["dune" "runtest" "-p" name "-j" jobs] {with-test}
 ]
@@ -29,6 +29,7 @@ depends: [
   "cmdliner"
   "dune" {>= "2.2.0"}
   "fix"
+  "dune-build-info"
   "fpath"
   "menhir"
   "ocaml-migrate-parsetree" {>= "1.5.0"}