[rules] Factor out the calculation of build root.

Several plugins need to access this information, so we place it in
`gen_rules` for consistency.

Signed-off-by: Emilio Jesus Gallego Arias <e+git@x80.org>

src/coq_rules.ml

@@ -135,7 +135,7 @@ let setup_ml_deps ~lib_db libs =
 let coqlib_wrapper_name (s : Dune_file.Coq.t) =
   Lib_name.Local.to_string (snd s.name)
 
-let setup_rules ~sctx ~dir ~dir_contents (s : Dune_file.Coq.t) =
+let setup_rules ~sctx ~root_dir:_ ~dir ~dir_contents (s : Dune_file.Coq.t) =
 
   let scope = SC.find_scope_by_dir sctx dir in
 
@@ -203,16 +203,14 @@ let install_rules ~sctx ~dir s =
       None, Install.(Entry.make Section.Lib_root ~dst vofile))
     |> List.rev_append (coq_plugins_install_rules ~scope ~package ~dst_dir s)
 
-let coqpp_rules ~sctx ~dir (s : Dune_file.Coqpp.t) =
+let coqpp_rules ~sctx ~root_dir ~dir (s : Dune_file.Coqpp.t) =
 
-  let scope = SC.find_scope_by_dir sctx dir in
-  let base_dir = Scope.root scope in
   let cc = create_ccoq sctx ~dir in
 
   let mlg_rule m =
     let source = Path.relative dir (m ^ ".mlg") in
     let target = Path.relative dir (m ^ ".ml") in
     let args = Arg_spec.[Dep source; Hidden_targets [target]] in
-    Build.run ~dir:base_dir cc.coqpp args in
+    Build.run ~dir:root_dir cc.coqpp args in
 
   List.map ~f:mlg_rule s.modules

src/coq_rules.mli

@@ -8,6 +8,7 @@ open! Stdune
 
 val setup_rules
   :  sctx:Super_context.t
+  -> root_dir:Path.t
   -> dir:Path.t
   -> dir_contents:Dir_contents.t
   -> Dune_file.Coq.t
@@ -21,6 +22,7 @@ val install_rules
 
 val coqpp_rules
   :  sctx:Super_context.t
+  -> root_dir:Path.t
   -> dir:Path.t
   -> Dune_file.Coqpp.t
   -> (unit, Action.t) Build.t list

src/gen_rules.ml

@@ -70,6 +70,7 @@ module Gen(P : sig val sctx : Super_context.t end) = struct
   let gen_rules dir_contents cctxs
         { Dir_with_dune. src_dir; ctx_dir; data = stanzas
         ; scope; kind = dir_kind ; dune_version = _ } =
+    let root_dir = Scope.root scope in
     let expander = Super_context.expander sctx ~dir:ctx_dir in
     let for_stanza stanza =
       let dir = ctx_dir in
@@ -181,17 +182,14 @@ module Gen(P : sig val sctx : Super_context.t end) = struct
                       produced by this stanza are part of."
                })
         | Some cctx ->
-          Menhir_rules.gen_rules cctx m ~dir:ctx_dir
+          Menhir_rules.gen_rules cctx m ~root_dir ~dir:ctx_dir
         end
       | Coq.T m when Expander.eval_blang expander m.enabled_if ->
-        (* Format.eprintf "[coq] gen_rules called @\n%!"; *)
-        let dir = ctx_dir in
-        let coq_rules = Coq_rules.setup_rules ~sctx ~dir ~dir_contents m in
-        SC.add_rules ~dir:ctx_dir sctx coq_rules
+        Coq_rules.setup_rules ~sctx ~root_dir ~dir:ctx_dir ~dir_contents m
+        |> SC.add_rules ~dir:ctx_dir sctx
       | Coqpp.T m ->
-        let dir = ctx_dir in
-        let coqpp_rules = Coq_rules.coqpp_rules ~sctx ~dir m in
-        SC.add_rules ~dir:ctx_dir sctx coqpp_rules
+        Coq_rules.coqpp_rules ~sctx ~root_dir ~dir:ctx_dir m
+        |> SC.add_rules ~dir:ctx_dir sctx
       | _ -> ());
     let dyn_deps =
       let pred =

src/menhir.ml

@@ -322,12 +322,12 @@ let targets (stanza : Dune_file.Menhir.t) : string list =
 let module_names (stanza : Dune_file.Menhir.t) : Module.Name.t list =
   List.map (modules stanza) ~f:Module.Name.of_string
 
-let gen_rules ~dir cctx stanza =
+let gen_rules ~root_dir ~dir cctx stanza =
   let module R =
     Run (struct
       let cctx = cctx
       let dir = dir
-      let root_dir = Scope.root (Compilation_context.scope cctx)
+      let root_dir = root_dir
       let stanza = stanza
     end) in
   ()

src/menhir.mli

@@ -12,7 +12,8 @@ val module_names : Dune_file.Menhir.t -> Module.Name.t list
 
 (** Generate the rules for a [(menhir ...)] stanza. *)
 val gen_rules
-  :  dir:Path.t
+  :  root_dir:Path.t
+  -> dir:Path.t
   -> Compilation_context.t
   -> Dune_file.Menhir.t
   -> unit