ctypes 0.3: run commands in stanza directory

This creates version 0.3 of the ctypes field.

When used, commands are run in the directory where the corresponding
stanza is defined. This makes it possible to use relative directories.

Fixes ocaml#5325

Signed-off-by: Etienne Millon <me@emillon.org>

src/dune_rules/ctypes/ctypes_field.ml

@@ -5,7 +5,10 @@ let name = "ctypes"
 
 let syntax =
   Dune_lang.Syntax.create ~name ~desc:"the ctypes extension"
-    [ ((0, 1), `Since (3, 0)); ((0, 2), `Since (3, 4)) ]
+    [ ((0, 1), `Since (3, 0))
+    ; ((0, 2), `Since (3, 4))
+    ; ((0, 3), `Since (3, 7)) (* TODO: actually target a later version *)
+    ]
 
 module Build_flags_resolver = struct
   module Vendored = struct
@@ -140,6 +143,7 @@ type t =
   ; generated_types : Module_name.t
   ; generated_entry_point : Module_name.t
   ; deps : Dep_conf.t list
+  ; version : Syntax.Version.t
   }
 
 type Stanza.t += T of t
@@ -157,7 +161,8 @@ let decode =
      and+ generated_types = field_o "generated_types" Module_name.decode
      and+ generated_entry_point =
        field "generated_entry_point" Module_name.decode
-     and+ deps = field_o "deps" (repeat Dep_conf.decode) in
+     and+ deps = field_o "deps" (repeat Dep_conf.decode)
+     and+ version = Syntax.get_exn syntax in
      let external_library_name =
        External_lib_name.of_string external_library_name
      in
@@ -187,6 +192,7 @@ let decode =
            ~default:(Module_name.of_string "Types_generated")
      ; generated_entry_point
      ; deps = Option.value ~default:[] deps
+     ; version
      })
 
 let () =

src/dune_rules/ctypes/ctypes_field.mli

@@ -58,6 +58,7 @@ type t =
   ; generated_types : Module_name.t
   ; generated_entry_point : Module_name.t
   ; deps : Dep_conf.t list
+  ; version : Syntax.Version.t
   }
 
 type Stanza.t += T of t

src/dune_rules/ctypes/ctypes_rules.ml

@@ -155,7 +155,7 @@ let function_gen_gen ~expander
        ])
 
 let build_c_program ~foreign_archives_deps ~sctx ~dir ~source_files ~scope
-    ~cflags ~output ~deps =
+    ~cflags ~output ~deps ~version =
   let ctx = Super_context.context sctx in
   let open Memo.O in
   let* exe =
@@ -216,33 +216,54 @@ let build_c_program ~foreign_archives_deps ~sctx ~dir ~source_files ~scope
     in
     deps
   in
-  let build =
-    let absolute_path_hack p =
-      (* These normal path builder things construct relative paths like
-         _build/default/your/project/file.c but before dune runs gcc it actually
-         cds into _build/default, which fails, so we turn them into absolutes to
-         hack around it. *)
-      Path.relative (Path.build dir) p |> Path.to_absolute_filename
-    in
-    let action =
-      let open Action_builder.O in
-      let* include_args = Resolve.Memo.read include_args in
-      let* base_args = with_user_and_std_flags in
-      deps
-      >>> Action_builder.map cflags ~f:(fun cflags_args ->
-              let source_files = List.map source_files ~f:absolute_path_hack in
-              let output = absolute_path_hack output in
-              let args =
-                base_args @ cflags_args @ include_args @ source_files
-                @ [ "-o"; output ]
-              in
-              Action.run exe args)
-    in
-    Action_builder.with_file_targets action
-      ~file_targets:[ Path.Build.relative dir output ]
+  let action =
+    if version >= (0, 3) then
+      let args : _ Command.Args.t list =
+        [ Expand (fun ~dir:_ -> with_user_and_std_flags)
+        ; Expand (fun ~dir:_ -> cflags)
+        ; Expand (fun ~dir:_ -> Resolve.Memo.read include_args)
+        ; Deps
+            (List.map
+               ~f:(fun s -> Path.relative (Path.build dir) s)
+               source_files)
+        ; A "-o"
+        ; Target (Path.Build.relative dir output)
+        ]
+      in
+      let open Action_builder.With_targets.O in
+      Action_builder.with_no_targets deps
+      >>> Command.run ~dir:(Path.build dir) exe args
+    else
+      let build =
+        let absolute_path_hack p =
+          (* These normal path builder things construct relative paths like
+             _build/default/your/project/file.c but before dune runs gcc it actually
+             cds into _build/default, which fails, so we turn them into absolutes to
+             hack around it. *)
+          Path.relative (Path.build dir) p |> Path.to_absolute_filename
+        in
+        let action =
+          let open Action_builder.O in
+          let* include_args = Resolve.Memo.read include_args in
+          let* base_args = with_user_and_std_flags in
+          deps
+          >>> Action_builder.map cflags ~f:(fun cflags_args ->
+                  let source_files =
+                    List.map source_files ~f:absolute_path_hack
+                  in
+                  let output = absolute_path_hack output in
+                  let args =
+                    base_args @ cflags_args @ include_args @ source_files
+                    @ [ "-o"; output ]
+                  in
+                  Action.run exe args)
+        in
+        Action_builder.with_file_targets action
+          ~file_targets:[ Path.Build.relative dir output ]
+      in
+      Action_builder.With_targets.map ~f:Action.Full.make build
   in
-  Super_context.add_rule sctx ~dir
-    (Action_builder.With_targets.map ~f:Action.Full.make build)
+  Super_context.add_rule sctx ~dir action
 
 let program_of_module_and_dir ~dir program =
   let build_dir = Path.build dir in
@@ -261,7 +282,7 @@ let exe_link_only ~dir ~shared_cctx ~sandbox program ~deps =
   Exe.link_many ~link_args ~programs:[ program ]
     ~linkages:[ Exe.Linkage.native ] ~promote:None shared_cctx ~sandbox
 
-let gen_rules ~cctx ~(buildable : Buildable.t) ~loc ~scope ~dir ~sctx =
+let gen_rules ~cctx ~(buildable : Buildable.t) ~loc ~scope ~dir ~sctx ~version =
   let ctypes = Option.value_exn buildable.ctypes in
   let external_library_name = ctypes.external_library_name in
   let type_description_functor = ctypes.type_description.functor_ in
@@ -359,7 +380,7 @@ let gen_rules ~cctx ~(buildable : Buildable.t) ~loc ~scope ~dir ~sctx =
     let* () =
       build_c_program ~foreign_archives_deps ~sctx ~dir ~scope
         ~source_files:[ c_generated_types_cout_c ]
-        ~output:c_generated_types_cout_exe ~deps ~cflags
+        ~output:c_generated_types_cout_exe ~deps ~cflags ~version
     in
     Super_context.add_rule sctx ~loc:Loc.none ~dir
       (let stdout_to =

src/dune_rules/ctypes/ctypes_rules.mli

@@ -7,6 +7,7 @@ val gen_rules :
   -> scope:Scope.t
   -> dir:Path.Build.t
   -> sctx:Super_context.t
+  -> version:Syntax.Version.t
   -> unit Memo.t
 
 val ctypes_cclib_flags :

src/dune_rules/exe_rules.ml

@@ -191,15 +191,15 @@ let executables_rules ~sctx ~dir ~expander ~dir_contents ~scope ~compile_info
     | None ->
       Exe.build_and_link_many cctx ~programs ~linkages ~link_args ~o_files
         ~promote:exes.promote ~embed_in_plugin_libraries ~sandbox
-    | Some _ctypes ->
+    | Some { version; _ } ->
       (* Ctypes stubgen builds utility .exe files that need to share modules
          with this compilation context. To support that, we extract the one-time
          run bits from [Exe.build_and_link_many] and run them here, then pass
          that to the [Exe.link_many] call here as well as the Ctypes_rules. This
          dance is done to avoid triggering duplicate rule exceptions. *)
       let* () =
         let loc = fst (List.hd exes.Executables.names) in
-        Ctypes_rules.gen_rules ~cctx ~buildable ~loc ~sctx ~scope ~dir
+        Ctypes_rules.gen_rules ~cctx ~buildable ~loc ~sctx ~scope ~dir ~version
       in
       let* () = Module_compilation.build_all cctx in
       Exe.link_many ~programs ~linkages ~link_args ~o_files

src/dune_rules/lib_rules.ml

@@ -561,9 +561,9 @@ let rules (lib : Library.t) ~sctx ~dir_contents ~dir ~expander ~scope =
     let* () =
       match buildable.ctypes with
       | None -> Memo.return ()
-      | Some _ctypes ->
+      | Some { version; _ } ->
         Ctypes_rules.gen_rules ~loc:(fst lib.name) ~cctx ~buildable ~sctx ~scope
-          ~dir
+          ~dir ~version
     in
     library_rules lib ~local_lib ~cctx ~source_modules ~dir_contents
       ~compile_info

test/blackbox-tests/test-cases/ctypes/directories.t

@@ -74,3 +74,13 @@ We ensure that just `-I lib` or `-I .` are not enough on their own.
   $ echo "(-I .)" > lib/extra_flags.sexp
   $ dune build > /dev/null 2>&1
   [1]
+
+With 0.3, everything is relative to the directory.
+
+  $ cat > dune-project << EOF
+  > (lang dune 3.7)
+  > (using ctypes 0.3)
+  > EOF
+
+  $ echo "(-I .)" > lib/extra_flags.sexp
+  $ dune build