Support version stanzas in dune-project files

doc/project-layout-specification.rst

@@ -131,6 +131,15 @@ Sets the name of the project:
 
     (name <name>)
 
+version
+-------
+
+Sets the version of the project:
+
+.. code:: scheme
+
+    (version <version>)
+
 <package>.opam files
 ====================
 
@@ -185,25 +194,21 @@ defined in the workspace. While Jbuilder itself makes no use of version
 numbers, it can be use by external tools such as
 `ocamlfind <http://projects.camlcity.org/projects/findlib.html>`__.
 
-Jbuilder determines the version of a package by first looking in the
-``<package>.opam`` for a ``version`` variable. If not found, it will try
-to read the first line of a version file in the same directory as the
-``<package>.opam`` file. The version file is any file whose name is, in
-order in which they are looked for:
+Jbuilder determines the version of a package by trying the following
+methods in order:
 
--  ``<package>.version``
--  ``version``
--  ``VERSION``
+- it looks in the ``<package>.opam`` file for a ``version`` variable
+- it looks for a ``<package>.version`` file in the same directory and
+  reads the first line
+- it looks for the version specified in the ``dune-project`` if present
+- it looks for a ``version`` file and reads the first line
+- it looks for a ``VERSION`` file and reads the first line
 
-The version file can be generated by a user rule.
+``<package>.version``, ``version`` and ``VERSION`` files may be
+generated.
 
 If the version can't be determined, Jbuilder just won't assign one.
 
-Note that if you are using `Topkg <https://github.com/dbuenzli/topkg>`__
-as well in your project, you shouldn't manually set a version in your
-``<package>.opam`` file or write/generate on of the file listed above.
-See the section about :ref:`using-topkg` for more details.
-
 Odig conventions
 ----------------
 

src/dune_project.ml

@@ -2,7 +2,8 @@ open Import
 open Sexp.Of_sexp
 
 type t =
-  { name : string
+  { name    : string
+  ; version : string option
   }
 
 let filename = "dune-project"
@@ -32,7 +33,8 @@ let parse ~dir =
   record
     (lang >>= fun Dune_0_1 ->
      name ~dir >>= fun name ->
-     return { name })
+     field_o "version" string >>= fun version ->
+     return { name; version })
 
 let load ~dir =
   let fname = Path.relative dir filename in

src/dune_project.mli

@@ -3,7 +3,8 @@
 open Import
 
 type t =
-  { name : string
+  { name    : string
+  ; version : string option
   }
 
 val load : dir:Path.t -> t

src/install_rules.ml

@@ -44,6 +44,15 @@ module Gen(P : Install_params) = struct
        >>> Build.write_file_dyn
              (lib_dune_file ~dir:(Lib.src_dir lib) ~name:(Lib.name lib)))
 
+  let version_from_dune_project (pkg : Package.t) =
+    let dir = Path.append (SC.build_dir sctx) pkg.path in
+    let scope = Scope.info (SC.find_scope_by_dir sctx dir) in
+    scope.version
+
+  type version_method =
+    | File of string
+    | From_dune_project
+
   let init_meta () =
     SC.libs_by_package sctx
     |> Package.Name.Map.iter ~f:(fun ((pkg : Package.t), libs) ->
@@ -63,18 +72,25 @@ module Gen(P : Install_params) = struct
               let rec loop = function
                 | [] -> Build.return None
                 | candidate :: rest ->
-                  let p = Path.relative path candidate in
-                  Build.if_file_exists p
-                    ~then_:(Build.lines_of p
-                            >>^ function
-                            | ver :: _ -> Some ver
-                            | _ -> Some "")
-                    ~else_:(loop rest)
+                  match candidate with
+                  | File fn ->
+                    let p = Path.relative path fn in
+                    Build.if_file_exists p
+                      ~then_:(Build.lines_of p
+                              >>^ function
+                              | ver :: _ -> Some ver
+                              | _ -> Some "")
+                      ~else_:(loop rest)
+                  | From_dune_project ->
+                    match version_from_dune_project pkg with
+                    | None -> loop rest
+                    | Some _ as x -> Build.return x
               in
               loop
-                [ (Package.Name.to_string pkg.name) ^ ".version"
-                ; "version"
-                ; "VERSION"
+                [ File ((Package.Name.to_string pkg.name) ^ ".version")
+                ; From_dune_project
+                ; File "version"
+                ; File "VERSION"
                 ]
           in
           Super_context.Pkg_version.set sctx pkg get

src/jbuild.ml

@@ -92,15 +92,17 @@ module Scope_info = struct
     { name     : Name.t
     ; packages : Package.t Package.Name.Map.t
     ; root     : Path.t
+    ; version  : string option
     }
 
   let anonymous =
     { name     = None
     ; packages = Package.Name.Map.empty
     ; root     = Path.root
+    ; version  = None
     }
 
-  let make = function
+  let make ?version = function
     | [] -> anonymous
     | pkg :: rest as pkgs ->
       let name =
@@ -114,6 +116,7 @@ module Scope_info = struct
           Package.Name.Map.of_list_exn (List.map pkgs ~f:(fun pkg ->
             pkg.Package.name, pkg))
       ; root
+      ; version
       }
 
   let package_listing packages =

src/jbuild.mli

@@ -28,9 +28,10 @@ module Scope_info : sig
                                    scope. *)
     ; packages : Package.t Package.Name.Map.t
     ; root     : Path.t
+    ; version  : string option
     }
 
-  val make : Package.t list -> t
+  val make : ?version:string -> Package.t list -> t
 
   (** The anonymous represent the scope at the root of the workspace
       when the root of the workspace contains no [<package>.opam]

src/jbuild_load.ml

@@ -275,12 +275,17 @@ let load ?extra_ignored_subtrees ?(ignore_promoted_rules=false) () =
       match scope, project with
       | None, None -> assert false
       | Some _, None -> scope
-      | None, Some { name } ->
+      | None, Some { name; version } ->
         Some { name     = Some name
              ; packages = Package.Name.Map.empty
              ; root     = path
+             ; version
              }
-      | Some scope, Some { name } -> Some { scope with name = Some name })
+      | Some scope, Some { name; version } ->
+        Some { scope with
+               name = Some name
+             ; version
+             })
   in
 
   let scopes =