Add model, architecture, system as enabled_if vars

Now these variables can be used along with os_type in the enabled_if
field of libraries

Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

CHANGES.md

@@ -69,7 +69,8 @@ unreleased
   `%{ocaml-config:os_type}` (#1764, @diml)
 
 - Allow `enabled_if` fields in `library` stanzas, restricted to the
-  `%{os_type}` variable (#1764, @diml)
+  `%{os_type}`, `%{model}`, `%{architecture}`, `%{system}` variables (#1764,
+  #2164 @diml, @rgrinberg)
 
 1.9.3 (06/05/2019)
 ------------------

doc/dune-files.rst

@@ -1097,6 +1097,12 @@ Dune supports the following variables:
   workspace file)
 - ``os_type`` is the type of the OS the build is targetting. This is
   the same as ``ocaml-config:os_type``
+- ``architecture`` is the type of the architecture the build is targetting. This
+  is the same as ``ocaml-config:architecture``
+- ``model`` is the type of the cpu the build is targetting. This is
+  the same as ``ocaml-config:model``
+- ``system`` is the name of the OS the build is targetting. This is the same as
+  ``ocaml-config:system``
 
 In addition, ``(action ...)`` fields support the following special variables:
 

src/context.ml

@@ -85,6 +85,7 @@ type t =
   ; ext_dll                 : string
   ; ext_exe                 : string
   ; os_type                 : string
+  ; model                   : string
   ; default_executable_name : string
   ; host                    : string
   ; target                  : string
@@ -473,6 +474,7 @@ let create ~(kind : Kind.t) ~path ~env ~env_nodes ~name ~merlin ~targets
       ; ext_dll                 = Ocaml_config.ext_dll                 ocfg
       ; ext_exe                 = Ocaml_config.ext_exe                 ocfg
       ; os_type                 = Ocaml_config.os_type                 ocfg
+      ; model                   = Ocaml_config.model                   ocfg
       ; default_executable_name = Ocaml_config.default_executable_name ocfg
       ; host                    = Ocaml_config.host                    ocfg
       ; target                  = Ocaml_config.target                  ocfg
@@ -703,4 +705,7 @@ let lib_config t =
   ; ext_obj = t.ext_obj
   ; ext_lib = t.ext_lib
   ; os_type = t.os_type
+  ; architecture = t.architecture
+  ; system = t.system
+  ; model = t.model
   }

src/context.mli

@@ -109,6 +109,7 @@ type t =
   ; ext_dll                 : string
   ; ext_exe                 : string
   ; os_type                 : string
+  ; model                   : string
   ; default_executable_name : string
   ; host                    : string
   ; target                  : string

src/dune_file.ml

@@ -1028,11 +1028,14 @@ module Library = struct
            Blang.fold_vars enabled_if ~init:() ~f:(fun var () ->
              match String_with_vars.Var.name var,
                    String_with_vars.Var.payload var with
-             | "os_type", None -> ()
+             | var, None when
+                 List.mem var ~set:Lib_config.allowed_in_enabled_if -> ()
              | _ ->
                Errors.fail (String_with_vars.Var.loc var)
-                 "Only the 'os_type' variable is allowed in the 'enabled_if' \
-                  field of libraries.");
+                 "Only %s are allowed in the 'enabled_if' \
+                  field of libraries."
+                 (String.enumerate_and Lib_config.allowed_in_enabled_if)
+           );
            { name
            ; public
            ; synopsis

src/lib_config.ml

@@ -5,4 +5,23 @@ type t =
   ; ext_lib : string
   ; ext_obj : string
   ; os_type : string
+  ; architecture : string
+  ; system : string
+  ; model : string
   }
+
+let var_map =
+  [ "architecture", (fun t -> t.architecture)
+  ; "system", (fun t -> t.system)
+  ; "model", (fun t -> t.model)
+  ; "os_type", (fun t -> t.os_type)
+  ]
+
+let allowed_in_enabled_if = List.map ~f:fst var_map
+
+let get_for_enabled_if t ~var =
+  match List.assoc var_map var with
+  | Some f -> f t
+  | None ->
+    Exn.code_error "Lib_config.get_for_enabled_if: var not allowed"
+      ["var", Sexp.Encoder.string var]

src/lib_config.mli

@@ -0,0 +1,13 @@
+type t =
+  { has_native : bool
+  ; ext_lib : string
+  ; ext_obj : string
+  ; os_type : string
+  ; architecture : string
+  ; system : string
+  ; model : string
+  }
+
+val allowed_in_enabled_if : string list
+
+val get_for_enabled_if : t -> var:string -> string

src/lib_info.ml

@@ -93,7 +93,8 @@ let user_written_deps t =
     ~f:(fun acc s -> Dune_file.Lib_dep.Direct s :: acc)
 
 let of_library_stanza ~dir
-      ~lib_config:{ Lib_config.has_native; ext_lib; ext_obj; os_type}
+      ~lib_config:({ Lib_config.has_native; ext_lib; ext_obj; _ }
+                   as lib_config)
       (conf : Dune_file.Library.t) =
   let (_loc, lib_name) = conf.name in
   let obj_dir =
@@ -166,7 +167,9 @@ let of_library_stanza ~dir
       Blang.eval conf.enabled_if ~dir ~f:(fun v _ver ->
         match String_with_vars.Var.name v,
               String_with_vars.Var.payload v with
-        | "os_type", None -> Some [String os_type]
+        | var, None ->
+          let value = Lib_config.get_for_enabled_if lib_config ~var in
+          Some [String value]
         | _ -> None)
     in
     if not enabled_if_result then

src/pform.ml

@@ -210,6 +210,12 @@ module Map = struct
       ; "ROOT"           , renamed_in ~version:(1, 0) ~new_name:"workspace_root"
       ; "os_type"        , since ~version:(1, 10)
                              (Var.Values [String context.os_type])
+      ; "architecture"   , since ~version:(1, 10)
+                             (Var.Values [String context.architecture])
+      ; "system"         , since ~version:(1, 10)
+                             (Var.Values [String context.system])
+      ; "model"          , since ~version:(1, 10)
+                             (Var.Values [String context.model])
       ]
     in
     { vars =