Quick fix multiple definitions of the same library when several scope…

…s define the same library.

Signed-off-by: Lucas Pluvinage <lucas.pluvinage@gmail.com>
Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

src/lib.ml

@@ -762,6 +762,10 @@ let rec find_implementation_for db lib ~variants =
       ~f:(fun variant acc ->
         List.rev_append acc
           (Variant.Map.Multi.find available_implementations variant))
+    |> List.sort_uniq ~compare:(fun (a:Lib_info.t) (b:Lib_info.t) ->
+      match Lib_name.compare a.name b.name with
+      | Eq -> Path.compare a.src_dir b.src_dir
+      | x -> x)
     |> fun x -> match x, db.parent with
     | [], None -> Ok None
     | [], Some db -> find_implementation_for db lib ~variants

src/stdune/list.ml

@@ -111,6 +111,9 @@ let sort t ~compare =
 let stable_sort t ~compare =
   stable_sort t ~cmp:(fun a b -> Ordering.to_int (compare a b))
 
+let sort_uniq t ~compare =
+  sort_uniq t ~cmp:(fun a b -> Ordering.to_int (compare a b))
+
 let rec compare a b ~compare:f : Ordering.t =
   match a, b with
   | [], [] -> Eq

src/stdune/list.mli

@@ -41,6 +41,7 @@ val destruct_last : 'a t -> ('a list * 'a) option
 
 val        sort : 'a t -> compare:('a -> 'a -> Ordering.t) -> 'a t
 val stable_sort : 'a t -> compare:('a -> 'a -> Ordering.t) -> 'a t
+val   sort_uniq : 'a t -> compare:('a -> 'a -> Ordering.t) -> 'a t
 
 val compare : 'a t -> 'a t -> compare:('a -> 'a -> Ordering.t) -> Ordering.t
 

test/blackbox-tests/test-cases/variants/run.t

@@ -82,12 +82,3 @@ Solving variant ambiguity by specifying a concrete implementation.
 Don't fail when the same library is defined in multiple scopes.
   $ dune build --root same-lib-in-multiple-scopes
   Entering directory 'same-lib-in-multiple-scopes'
-  File "dune", line 3, characters 12-16:
-  3 |   (variants unix)
-                  ^^^^
-  Error: Multiple solutions for the implementation
-  of test  with variants [ "unix" ]
-  -> test-unix ("unix")
-  -> test-unix ("unix")
-  -> required by executable exe in dune:2
-  [1]