Fix bigarray config (#5494)

src/dune_rules/lib.ml

@@ -1173,6 +1173,23 @@ end = struct
       { resolved; selects; re_exports }
   end
 
+  let remove_library deps target =
+    List.filter_map deps ~f:(fun (dep : Lib_dep.t) ->
+        match dep with
+        | Re_export (_, name) | Direct (_, name) ->
+          Option.some_if (not (Lib_name.equal target name)) dep
+        | Select select ->
+          let choices =
+            List.filter_map select.choices ~f:(fun choice ->
+                if Lib_name.Set.mem choice.forbidden target then None
+                else
+                  Some
+                    { choice with
+                      required = Lib_name.Set.remove choice.required target
+                    })
+          in
+          Some (Select { select with choices }))
+
   let resolve_complex_deps db deps ~private_deps : resolved_deps Memo.t =
     let resolve_select { Lib_dep.Select.result_fn; choices; loc } =
       let open Memo.O in
@@ -1207,6 +1224,16 @@ end = struct
     in
     let open Memo.O in
     let open Resolved_deps_builder in
+    let deps =
+      let ocaml_version = db.lib_config.ocaml_version in
+      let bigarray_in_std_libraries =
+        Ocaml.Version.has_bigarray_library ocaml_version
+      in
+      if bigarray_in_std_libraries then deps
+      else
+        let bigarray = Lib_name.of_string "bigarray" in
+        remove_library deps bigarray
+    in
     let+ builder =
       Memo.List.fold_left deps ~init:empty ~f:(fun acc dep ->
           match (dep : Lib_dep.t) with

test/blackbox-tests/test-cases/bigarray.t/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.t/a/dune

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

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

@@ -0,0 +1,5 @@
+let _c1 = B_lib.v
+
+let _c2 = Bigarray.C_layout_typ
+
+let () = Printf.eprintf "Welcome to b\n%!"

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

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

test/blackbox-tests/test-cases/bigarray.t/b/dune

@@ -0,0 +1,10 @@
+(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.t/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.t/c/c.dummy.ml

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

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

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

test/blackbox-tests/test-cases/bigarray.t/c/dune

@@ -0,0 +1,9 @@
+(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.t/dune-project

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

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

@@ -0,0 +1,33 @@
+This tests the support for the bigarray atom in the dune libraries stanza.
+
+History:
+- OCaml 4.05 ([ocaml/ocaml#997](https://github.com/ocaml/ocaml/pull/997) and
+[ocaml/ocaml#1077](https://github.com/ocaml/ocaml/pull/1077)) add
+`Unix.map_file` allowing the `map_file` functions in `Bigarray` to be
+deprecated. Bigarray remains a separate library.
+- OCaml 4.07 ([ocaml/ocaml#1685](https://github.com/ocaml/ocaml/pull/1685))
+adds `Stdlib.Bigarray`, but without the `map_file` functions (since these
+required `Unix.file_descr`. The separate library remains with those
+functions (but still marked as deprecated). Code can be updated to use
+Unix.map_file and then Stdlib.Bigarray and not require the separate library
+at all, but the separate remains compatible with OCaml 4.06.
+- OCaml 4.08 ([ocaml/ocaml#2263](https://github.com/ocaml/ocaml/pull/2263))
+deletes the `map_file` functions completely, requiring _all_ code to be
+updated to use `Unix.map_file`, if appropriate. From this release, it is
+unnecessary to link with the separate Bigarray library.
+- OCaml 5.00 ([ocaml/ocaml#10896](https://github.com/ocaml/ocaml/pull/10896)
+removes the separate Bigarray library.
+
+Code may be written which is designed to support both OCaml 4.06 and earlier and
+also OCaml 5.0+. In such cases, it is appropriate to have `(libraries bigarray)`
+even though there is no Bigarray library in OCaml 5.
+
+This test uses `(libraries bigarray)` (the program uses `Bigarray`)
+  $ dune exec a/a.exe
+  Welcome to a
+This test uses `(libraries (re_export bigarray))` similarly
+  $ dune exec b/b.exe
+  Welcome to b
+This test uses a `(select )` construct and should always select bigarray support
+  $ dune exec c/c.exe
+  Welcome to c WITH bigarray support