Fix bigarray config ocaml#5494

"Select" rule prevent the case when we endup on require and forbiden
empty. Skipping bigarray could result having require and forbiden empty
that case is the same as no literals "(_ -> dummy)".

Some test-cases for "Direct", "Re-export" and "Select"

Signed-off-by: Alpha DIALLO <[email protected]>
Signed-off-by: Etienne Millon <[email protected]>

src/dune_rules/lib.ml

@@ -1219,7 +1219,8 @@ end = struct
               let forbidden = Lib_name.Set.to_list forbidden in
               if
                 List.exists
-                  ~f:(fun lib -> is_bigarray lib && bigarray_in_std_libraries)
+                  ~f:(fun lib ->
+                    is_bigarray lib && not bigarray_in_std_libraries)
                   forbidden
               then Memo.return None
               else
@@ -1228,21 +1229,30 @@ end = struct
                 in
                 if exists then Memo.return None
                 else
-                  let required =
-                    Lib_name.Set.filter
-                      ~f:(fun lib ->
-                        (not (is_bigarray lib)) || bigarray_in_std_libraries)
-                      required
+                  let found, required =
+                    ( Lib_name.Set.mem required (Lib_name.of_string "bigarray")
+                    , Lib_name.Set.filter
+                        ~f:(fun lib ->
+                          (not (is_bigarray lib)) || bigarray_in_std_libraries)
+                        required )
                   in
-                  Resolve.Memo.peek
-                    (let deps =
-                       Lib_name.Set.fold required ~init:[] ~f:(fun x acc ->
-                           (loc, x) :: acc)
-                     in
-                     resolve_simple_deps ~private_deps db deps)
-                  >>| function
-                  | Ok ts -> Some (ts, file)
-                  | Error () -> None)
+                  if
+                    Lib_name.Set.is_empty required
+                    && found
+                    && not bigarray_in_std_libraries
+                  then Memo.return None
+                    (*avoid the case where forbidden and required are empty, so
+                      it switch in case "(_ -> dummy)"*)
+                  else
+                    Resolve.Memo.peek
+                      (let deps =
+                         Lib_name.Set.fold required ~init:[] ~f:(fun x acc ->
+                             (loc, x) :: acc)
+                       in
+                       resolve_simple_deps ~private_deps db deps)
+                    >>| function
+                    | Ok ts -> Some (ts, file)
+                    | Error () -> None)
         in
         let get which =
           let res = select |> Option.map ~f:which in

test/blackbox-tests/test-cases/bigarray-skip/a/a.ml

@@ -0,0 +1,3 @@
+let _c = Bigarray.C_layout_typ
+
+let () = Printf.eprintf "Welcome to a\n%!"

test/blackbox-tests/test-cases/bigarray-skip/a/dune

@@ -0,0 +1,3 @@
+(executable
+  (name a)
+  (libraries bigarray))

test/blackbox-tests/test-cases/bigarray-skip/b/b.ml

@@ -0,0 +1,4 @@
+let _c1 = B_lib.v
+let _c2 = Bigarray.C_layout_typ
+
+let () = Printf.eprintf "Welcome to b\n%!"

test/blackbox-tests/test-cases/bigarray-skip/b/b_lib.ml

@@ -0,0 +1 @@
+let v = Bigarray.C_layout_typ

test/blackbox-tests/test-cases/bigarray-skip/b/dune

@@ -0,0 +1,9 @@
+(library
+  (name b_lib)
+  (libraries (re_export bigarray))
+  (modules b_lib))
+
+(executable
+  (name b)
+  (libraries b_lib)
+  (modules b))

test/blackbox-tests/test-cases/bigarray-skip/c/c.bigarray.ml

@@ -0,0 +1,3 @@
+let _c = Bigarray.C_layout_typ
+
+let () = Printf.eprintf "Welcome to c WITH bigarray support\n%!"

test/blackbox-tests/test-cases/bigarray-skip/c/c.dummy.ml

@@ -0,0 +1 @@
+let () = Printf.eprintf "Welcome to c with nothing inferred\n%!"

test/blackbox-tests/test-cases/bigarray-skip/c/c.nobigarray.ml

@@ -0,0 +1 @@
+let () = Printf.eprintf "Welcome to c WITHOUT bigarray support\n%!"

test/blackbox-tests/test-cases/bigarray-skip/c/dune

@@ -0,0 +1,3 @@
+(executable
+  (name c)
+  (libraries (select c.ml from (!bigarray -> c.nobigarray.ml) (bigarray -> c.bigarray.ml) ( -> c.dummy.ml))))

test/blackbox-tests/test-cases/bigarray-skip/dune-project

@@ -0,0 +1,3 @@
+(lang dune 3.0)
+
+(implicit_transitive_deps false)

test/blackbox-tests/test-cases/bigarray-skip/run.t

@@ -0,0 +1,19 @@
+Bigarray library is included in the Standard libraries since OCaml 5.00.0.
+And now dune skip it by #5526 PR when included in libraries doing like "(libraries bigarray)".
+
+  $ dummy="_build/default/c/c.dummy.ml"
+  $ found="$(ocamlfind query bigarray -p-format)_found"
+  $ cat > done.sh <<EOF
+  > #!/usr/bin/env bash
+  > if [[ "$found" != "bigarray_found" && -e $dummy ]]; then
+  >   echo "Success skipping bigarray"
+  > elif [[ "$found" != "bigarray_found" && ! -e $dummy ]]; then
+  >   echo "Fail skipping bigarray"
+  > else
+  >   echo "Success skipping bigarray"
+  > fi
+  > EOF
+  $ dune build @install
+  $ chmod +x done.sh
+  $ ./done.sh
+  Success skipping bigarray