refactor(pkg): introduce Lock_dir.uses_versioned_paths

Signed-off-by: Ali Caglayan <alizter@gmail.com>

Author: Alizter

src/dune_pkg/lock_dir.ml

@@ -1116,6 +1116,10 @@ let to_dyn
     ]
 ;;
 
+(* CR-someday Alizter: Remove this when portable lock directories are
+   consolidated with non-portable lock directories. *)
+let uses_versioned_paths t = not (List.is_empty (snd t.solved_for_platforms))
+
 type missing_dependency =
   { dependant_package : Pkg.t
   ; dependency : Package_name.t

src/dune_pkg/lock_dir.mli

@@ -117,6 +117,11 @@ val remove_locs : t -> t
 val equal : t -> t -> bool
 val to_dyn : t -> Dyn.t
 
+(** Returns whether this lock directory uses versioned paths for package
+    files directories. Portable lock directories use versioned paths to
+    handle multiple versions of the same package. *)
+val uses_versioned_paths : t -> bool
+
 (** [create_latest_version packages ~ocaml ~repos
     ~expanded_solver_variable_bindings] raises a [Code_error] if [packages] is
     not closed under the "depends on" relationship between packages. Every

src/dune_rules/pkg_rules.ml

@@ -1530,10 +1530,10 @@ end = struct
       and+ files_dir =
         let+ lock_dir_path =
           Package_universe.lock_dir_path package_universe >>| Option.value_exn
-        and+ { solved_for_platforms = _, platforms; _ } =
-          Package_universe.lock_dir package_universe
+        and+ lock_dir = Package_universe.lock_dir package_universe in
+        let version =
+          Option.some_if (Dune_pkg.Lock_dir.uses_versioned_paths lock_dir) info.version
         in
-        let version = Option.some_if (not (List.is_empty platforms)) info.version in
         Dune_pkg.Lock_dir.Pkg.files_dir info.name version ~lock_dir:lock_dir_path
         |> Path.as_in_build_dir_exn
       in