fix(vlib): fix installation of vlib implementations

An implementation of a virtual library should include all the binary
artifacts of the virtual library. This commit adds the inheritd vlib
artifacts to the .install file.

Signed-off-by: Rudi Grinberg <me@rgrinberg.com>

CHANGES.md

@@ -1,6 +1,9 @@
 Unreleased
 ----------
 
+- Fix installation of implementations of virtual libraries (#5150, fix #3636,
+  @rgrinberg)
+
 - Run tests in all modes defined. Previously, jsoo was excluded. (@hhugo,
   #5049, fix #4951)
 

src/dune_rules/install_rules.ml

@@ -117,12 +117,16 @@ end = struct
       Install.Entry.Sourced.create ~loc entry
     in
     let* installable_modules =
-      let+ ml_sources = Dir_contents.ocaml dir_contents in
-      Ml_sources.modules ml_sources ~for_:(Library (Library.best_name lib))
-      |> Modules.fold_no_vlib ~init:[] ~f:(fun m acc -> m :: acc)
+      let* ml_sources = Dir_contents.ocaml dir_contents in
+      let modules =
+        Ml_sources.modules ml_sources ~for_:(Library (Library.best_name lib))
+      in
+      let+ impl = Virtual_rules.impl sctx ~lib ~scope in
+      let modules = Vimpl.impl_modules impl modules in
+      Modules.split_by_lib modules
     in
     let sources =
-      List.concat_map installable_modules ~f:(fun m ->
+      List.concat_map installable_modules.impl ~f:(fun m ->
           List.map (Module.sources m) ~f:(fun source ->
               (* We add the -gen suffix to a few files generated by dune, such
                  as the alias module. *)
@@ -153,7 +157,8 @@ end = struct
           Path.basename dir' |> inside_subdir |> Option.some
       in
       let virtual_library = Library.is_virtual lib in
-      List.concat_map installable_modules ~f:(fun m ->
+      let modules =
+        let common m =
           let cm_file kind = Obj_dir.Module.cm_file obj_dir m ~kind in
           let if_ b (cm_kind, f) =
             if b then
@@ -163,21 +168,38 @@ end = struct
             else
               []
           in
-          let cm_dir = cm_dir m in
           let open Cm_kind in
           [ if_ true (Cmi, cm_file Cmi)
           ; if_ native (Cmx, cm_file Cmx)
           ; if_ (byte && virtual_library) (Cmo, cm_file Cmo)
           ; if_
               (native && virtual_library)
               (Cmx, Obj_dir.Module.o_file obj_dir m ~ext_obj)
-          ; List.filter_map Ml_kind.all ~f:(fun ml_kind ->
-                let open Option.O in
-                let+ cmt = Obj_dir.Module.cmt_file obj_dir m ~ml_kind in
-                (Cmi, cmt))
           ]
           |> List.concat
-          |> List.map ~f:(fun (cm_kind, f) -> (cm_dir cm_kind, f)))
+        in
+        let set_dir m =
+          List.map ~f:(fun (cm_kind, p) -> (cm_dir m cm_kind, p))
+        in
+        let modules_impl =
+          List.concat_map installable_modules.impl ~f:(fun m ->
+              common m
+              @ List.filter_map Ml_kind.all ~f:(fun ml_kind ->
+                    let open Option.O in
+                    let+ cmt = Obj_dir.Module.cmt_file obj_dir m ~ml_kind in
+                    (Cm_kind.Cmi, cmt))
+              |> set_dir m)
+        in
+        let modules_vlib =
+          List.concat_map installable_modules.vlib ~f:(fun m ->
+              if Module.kind m = Virtual then
+                []
+              else
+                common m |> set_dir m)
+        in
+        modules_vlib @ modules_impl
+      in
+      modules
     in
     let* lib_files, dll_files =
       let+ lib_files = lib_files ~dir ~dir_contents ~lib_config info in

src/dune_rules/modules.ml

@@ -618,6 +618,29 @@ let rec fold_no_vlib t ~init ~f =
   | Wrapped w -> Wrapped.fold w ~init ~f
   | Impl { vlib = _; impl } -> fold_no_vlib impl ~f ~init
 
+let rec map t ~f =
+  match t with
+  | Stdlib w -> Stdlib (Stdlib.map w ~f)
+  | Singleton m -> Singleton (f m)
+  | Unwrapped m -> Unwrapped (Module_name.Map.map m ~f)
+  | Wrapped w -> Wrapped (Wrapped.map w ~f)
+  | Impl { vlib; impl } -> Impl { vlib = map vlib ~f; impl = map impl ~f }
+
+type split_by_lib =
+  { vlib : Module.t list
+  ; impl : Module.t list
+  }
+
+let split_by_lib t =
+  let f m acc = m :: acc in
+  let init = [] in
+  match t with
+  | Impl { vlib; impl } ->
+    let vlib = fold_no_vlib vlib ~init ~f in
+    let impl = fold_no_vlib impl ~init ~f in
+    { vlib; impl }
+  | _ -> { impl = fold_no_vlib t ~init ~f; vlib = [] }
+
 let compat_for_exn t m =
   match t with
   | Singleton _

src/dune_rules/modules.mli

@@ -57,6 +57,8 @@ val fold_user_written : t -> f:(Module.t -> 'acc -> 'acc) -> init:'acc -> 'acc
 val map_user_written :
   t -> f:(Module.t -> Module.t Memo.Build.t) -> t Memo.Build.t
 
+val map : t -> f:(Module.t -> Module.t) -> t
+
 val fold_user_available : t -> f:(Module.t -> 'acc -> 'acc) -> init:'acc -> 'acc
 
 (** Returns all the compatibility modules. *)
@@ -112,5 +114,12 @@ val as_singleton : t -> Module.t option
 
 val source_dirs : t -> Path.Set.t
 
+type split_by_lib =
+  { vlib : Module.t list
+  ; impl : Module.t list
+  }
+
+val split_by_lib : t -> split_by_lib
+
 (** [has_impl t] is true if there's at least one implementation in [t]*)
 val has_impl : t -> bool

test/blackbox-tests/test-cases/virtual-libraries/dune-package-info.t/run.t

@@ -14,6 +14,8 @@ Include variants and implementation information in dune-package
      impl/impl$ext_lib
      impl/impl.cma
      impl/impl.cmxa
+     impl/vlib.cmi
+     impl/vlib.cmx
      impl/vlib__Vmod.cmi
      impl/vlib__Vmod.cmt
      impl/vlib__Vmod.cmx

test/blackbox-tests/test-cases/virtual-libraries/implements-external.t/run.t

@@ -45,9 +45,6 @@ modules remain hidden.
   > Vlib.Foo.run ()
   > EOF
   $ dune exec ./blah.exe
-  File "blah.ml", line 1, characters 0-12:
-  1 | Vlib.Foo.run ()
-      ^^^^^^^^^^^^
-  Error: Unbound module Vlib
-  [1]
+  bar from vlib
+  Foo.run implemented
   $ cd ..

test/blackbox-tests/test-cases/virtual-libraries/install-file.t/run.t

@@ -22,6 +22,8 @@ Install files for implementations and virtual libs have all the artifacts:
     "_build/install/default/lib/impl/impl.cma"
     "_build/install/default/lib/impl/impl.cmxa"
     "_build/install/default/lib/impl/opam"
+    "_build/install/default/lib/impl/vlib.cmi"
+    "_build/install/default/lib/impl/vlib.cmx"
     "_build/install/default/lib/impl/vlib__Foo.cmi"
     "_build/install/default/lib/impl/vlib__Foo.cmt"
     "_build/install/default/lib/impl/vlib__Foo.cmx"

test/blackbox-tests/test-cases/virtual-libraries/vlib-default-impl.t/run.t

@@ -35,6 +35,8 @@ Check that default implementation data is installed in the dune package file.
      a$ext_obj
      a__X.cmi
      a__X.cmti
+     default-impl/a.cmi
+     default-impl/a.cmx
      default-impl/a__X.cmi
      default-impl/a__X.cmt
      default-impl/a__X.cmx