Fix #15

When there are no <pkg>.opam files in parent directories, use the
whole workspace as scope

doc/manual.org

@@ -656,9 +656,9 @@ always prefered to ones that are part of the installed world.
 
 The scope of internal library names is not the whole workspace. It is
 restricted to the sub-tree starting from the closest parent containing
-a =<package>.opam= file. Moreover, a sub-tree containing
-=<package>.opam= doesn' t inherit the internal names available in its
-parent scope.
+a =<package>.opam= file, or the whole workspace if no such directory
+exist. Moreover, a sub-tree containing =<package>.opam= doesn' t
+inherit the internal names available in its parent scope.
 
 The idea behing this rule is that public library names must be
 universally unique, but internal ones don't need to. In particular you

src/lib_db.ml

@@ -16,6 +16,8 @@ let rec internal_name_scope t ~dir =
   match Hashtbl.find t.by_internal_name dir with
   | Some scope -> scope
   | None ->
+    (* [create] ensures that [Hashtbl.find t.by_internal_name Path.root] is [Some _] so
+       this [Path.parent dir] is never called with [Path.root] *)
     let scope = internal_name_scope t ~dir:(Path.parent dir) in
     Hashtbl.add t.by_internal_name ~key:dir ~data:scope;
     scope
@@ -98,8 +100,9 @@ let create findlib ~dirs_with_dot_opam_files internal_libraries =
     ; instalable_internal_libs = String_map.empty
     }
   in
-  (* Initializes the scopes *)
-  Path.Set.iter dirs_with_dot_opam_files ~f:(fun dir ->
+  (* Initializes the scopes, including [Path.root] so that when there are no <pkg>.opam
+     files in parent directories, the scope is the whole workspace. *)
+  Path.Set.iter (Path.add Path.root dirs_with_dot_opam_files) ~f:(fun dir ->
     Hashtbl.add t.by_internal_name ~key:dir
       ~data:(ref String_map.empty));
   List.iter internal_libraries ~f:(fun ((dir, lib) as internal) ->