Install by specifying libdir for opam-installer

- change default findlib directory (ocamlc -where)

bin/main.ml

@@ -685,12 +685,20 @@ let get_prefix context ~from_command_line =
   | Some p -> Future.return (Path.of_string p)
   | None -> Context.install_prefix context
 
+let get_libdir context ~libdir_from_command_line ~prefix_from_command_line =
+  match libdir_from_command_line with
+  | Some p -> Future.return (Path.of_string p)
+  | None ->
+    match prefix_from_command_line with
+    | Some p -> Future.return (Path.relative (Path.of_string p) "lib")
+    | None -> Context.install_ocaml_libdir context
+
 let install_uninstall ~what =
   let doc =
     sprintf "%s packages using opam-installer." (String.capitalize_ascii what)
   in
   let name_ = Arg.info [] ~docv:"PACKAGE" in
-  let go common prefix pkgs =
+  let go common prefix_from_command_line libdir_from_command_line pkgs =
     set_common common ~targets:[];
     let opam_installer = opam_installer () in
     let log = Log.create () in
@@ -720,15 +728,16 @@ let install_uninstall ~what =
               (List.map missing_install_files
                  ~f:(fun p -> sprintf "- %s" (Path.to_string p))))
        end;
-       (match setup.contexts, prefix with
-        | _ :: _ :: _, Some _ ->
-          die "Cannot specify --prefix when installing into multiple contexts!"
+       (match setup.contexts, prefix_from_command_line, libdir_from_command_line with
+        | _ :: _ :: _, Some _, _ | _ :: _ :: _, _, Some _ ->
+          die "Cannot specify --prefix or --libdir when installing into multiple contexts!"
         | _ -> ());
        let module CMap = Map.Make(Context) in
        let install_files_by_context = CMap.of_alist_multi install_files |> CMap.bindings in
        Future.all_unit
          (List.map install_files_by_context ~f:(fun (context, install_files) ->
-            get_prefix context ~from_command_line:prefix >>= fun prefix ->
+            get_prefix context ~from_command_line:prefix_from_command_line >>= fun prefix ->
+            get_libdir context ~libdir_from_command_line ~prefix_from_command_line >>= fun libdir ->
             Future.all_unit
               (List.map install_files ~f:(fun path ->
                    let purpose = Future.Build_job install_files in
@@ -736,12 +745,15 @@ let install_uninstall ~what =
                      [ sprintf "-%c" what.[0]
                      ; "--prefix"
                      ; Path.to_string prefix
+                     ; "--libdir"
+                     ; Path.to_string libdir
                      ; Path.to_string path
                      ])))))
   in
   ( Term.(const go
           $ common
           $ Arg.(value & opt (some dir) None & info ["prefix"])
+          $ Arg.(value & opt (some dir) None & info ["libdir"])
           $ Arg.(value & pos_all string [] name_))
   , Term.info what ~doc ~man:help_secs)
 

doc/usage.rst

@@ -248,17 +248,27 @@ to be able to use ``jbuilder install``.
 Destination
 -----------
 
-The place where the build artifacts are copied, usually referred as
+The place where the build artifacts (except ocaml libraries) are copied, usually referred as
 **prefix**, is determined as follow for a given build context:
 
 #. if an explicit ``--prefix <path>`` argument is passed, use this path
 #. if ``opam`` is present in the ``PATH``, use the output of ``opam config var
    prefix``
-#. otherwise, take the directory where ``ocamlc`` was found, and append
-   ``../lib`` to it. For instance if ``ocamlc`` is found in ``/usr/bin``, use
-   ``/usr``
+#. otherwise, take the parent of the directory where ``ocamlc`` was found.
 
-Note that ``--prefix`` is only supported if a single build context is in
+The ocaml libraries build artifacts are copied, referred as
+**libdir**, is determined as follow for a given build context:
+
+#. if an explicit ``--libdir <path>`` argument is passed, use this path
+#. if ``ocamlfind`` is present in the ``PATH``, use the output of
+   ``ocamlfind printconf destdir``
+#. if ``opam`` is present in the ``PATH``, use the output of ``opam config var
+   lib``
+#. otherwise, take the directory of the ocaml standard library
+
+
+
+Note that ``--prefix`` and ``--libdir`` are only supported if a single build context is in
 use.
 
 Workspace configuration

src/context.ml

@@ -198,31 +198,8 @@ let create ~(kind : Kind.t) ~path ~base_env ~env_extra ~name ~merlin ~use_findli
     Path.of_string (sprintf "_build/%s" name)
   in
   let ocamlc_config_cmd = sprintf "%s -config" (Path.to_string ocamlc) in
-  let findlib_path =
-    if use_findlib then
-      (* If ocamlfind is present, it has precedence over everything else. *)
-      match which "ocamlfind" with
-      | Some fn ->
-        (Future.run_capture_lines ~env Strict
-           (Path.to_string fn) ["printconf"; "path"]
-         >>| List.map ~f:Path.absolute)
-      | None ->
-        (* If there no ocamlfind in the PATH, check if we have opam and assume a standard
-           opam setup *)
-        opam_config_var ~env ~cache:opam_var_cache "lib"
-        >>| function
-        | Some s -> [Path.absolute s]
-        | None ->
-          (* If neither opam neither ocamlfind are present, assume that libraries are in
-             [dir ^ "/../lib"] *)
-          [Path.relative (Path.parent dir) "lib"]
-    else
-      return []
-  in
-  both
-    findlib_path
-    (Future.run_capture_lines ~env Strict (Path.to_string ocamlc) ["-config"])
-  >>= fun (findlib_path, ocamlc_config) ->
+  Future.run_capture_lines ~env Strict (Path.to_string ocamlc) ["-config"]
+  >>= fun ocamlc_config ->
   let ocamlc_config =
     List.map ocamlc_config ~f:(fun line ->
       match String.index line ':' with
@@ -301,6 +278,28 @@ let create ~(kind : Kind.t) ~path ~base_env ~env_extra ~name ~merlin ~use_findli
       let _, ocamlopt_cflags = split_prog (get "native_c_compiler") in
       (c_compiler, ocamlc_cflags, ocamlopt_cflags)
   in
+  let findlib_path =
+    if use_findlib then
+      (* If ocamlfind is present, it has precedence over everything else. *)
+      match which "ocamlfind" with
+      | Some fn ->
+        (Future.run_capture_lines ~env Strict
+           (Path.to_string fn) ["printconf"; "path"]
+         >>| List.map ~f:Path.absolute)
+      | None ->
+        (* If there no ocamlfind in the PATH, check if we have opam and assume a standard
+           opam setup *)
+        opam_config_var ~env ~cache:opam_var_cache "lib"
+        >>| function
+        | Some s -> [Path.absolute s]
+        | None ->
+          (* If neither opam neither ocamlfind are present, assume that libraries are in
+             the stdlib directory *)
+          [stdlib_dir]
+    else
+      return []
+  in
+  findlib_path >>= fun findlib_path ->
   return
     { name
     ; kind
@@ -426,6 +425,23 @@ let install_prefix t =
   | Some x -> Path.absolute x
   | None   -> Path.parent t.ocaml_bin
 
+let install_ocaml_libdir t =
+  (* If ocamlfind is present, it has precedence over everything else. *)
+  match which t "ocamlfind" with
+  | Some fn ->
+    (Future.run_capture_line ~env:t.env Strict
+       (Path.to_string fn) ["printconf"; "destdir"]
+     >>| Path.absolute)
+  | None ->
+    (* If there no ocamlfind in the PATH, check if we have opam and assume a standard
+       opam setup *)
+    opam_config_var t "lib"
+    >>| function
+    | Some s -> Path.absolute s
+    | None ->
+      (* If neither opam neither ocamlfind are present use stdlib dir *)
+      t.stdlib_dir
+
 
 (* CR-someday jdimino: maybe we should just do this for [t.env] directly? *)
 let env_for_exec t =

src/context.mli

@@ -144,6 +144,7 @@ val extend_env : vars:string Env_var_map.t -> env:string array -> string array
 val opam_config_var : t -> string -> string option Future.t
 
 val install_prefix : t -> Path.t Future.t
+val install_ocaml_libdir : t -> Path.t Future.t
 
 val env_for_exec : t -> string array