feat(single-context): add melange.libraries

src/dune_rules/stanzas/buildable.ml

@@ -12,6 +12,7 @@ type t =
   ; melange_modules : Ordered_set_lang.Unexpanded.t option
   ; empty_module_interface_if_absent : bool
   ; libraries : Lib_dep.t list
+  ; melange_libraries : Lib_dep.t list option
   ; foreign_archives : (Loc.t * Foreign.Archive.t) list
   ; extra_objects : Foreign.Objects.t
   ; foreign_stubs : Foreign.Stubs.t list
@@ -125,6 +126,11 @@ let decode (for_ : for_) =
              >>> enter (maybe string))))
   and+ libraries =
     field "libraries" (Lib_dep.L.decode ~allow_re_export:in_library) ~default:[]
+  and+ melange_libraries =
+    field_o
+      "melange.libraries"
+      (Dune_lang.Syntax.since Stanza.syntax (3, 24)
+       >>> Lib_dep.L.decode ~allow_re_export:in_library)
   and+ flags = decode_ocaml_flags
   and+ js_of_ocaml =
     field
@@ -210,6 +216,7 @@ let decode (for_ : for_) =
   ; foreign_archives
   ; extra_objects
   ; libraries
+  ; melange_libraries
   ; flags
   ; js_of_ocaml = { js = js_of_ocaml; wasm = wasm_of_ocaml }
   ; allow_overlapping_dependencies

src/dune_rules/stanzas/buildable.mli

@@ -11,6 +11,7 @@ type t =
   ; melange_modules : Ordered_set_lang.Unexpanded.t option
   ; empty_module_interface_if_absent : bool
   ; libraries : Lib_dep.t list
+  ; melange_libraries : Lib_dep.t list option
   ; foreign_archives : (Loc.t * Foreign.Archive.t) list
   ; extra_objects : Foreign.Objects.t
   ; foreign_stubs : Foreign.Stubs.t list

src/dune_rules/stanzas/library.ml

@@ -453,6 +453,25 @@ let to_lib_id ~src_dir t =
   Lib_id.Local.make ~loc ~src_dir (Lib_name.of_local t.name)
 ;;
 
+let library_deps ~loc ~field ~modes ~libs ~melange_libs =
+  let ocaml, melange =
+    let { Lib_mode.Map.ocaml = { byte; native }; melange } = modes in
+    let ocaml_libraries = if byte || native then libs else [] in
+    let melange_libraries =
+      match melange, melange_libs with
+      | true, Some melange_libraries -> melange_libraries
+      | true, None -> libs
+      | false, None -> []
+      | false, Some _ ->
+        User_error.raise
+          ~loc
+          [ Pp.textf "Cannot specify `%s' without `melange' mode" field ]
+    in
+    ocaml_libraries, melange_libraries
+  in
+  { Compilation_mode.By_mode.ocaml; melange }
+;;
+
 let to_lib_info
       conf
       ~expander
@@ -576,14 +595,17 @@ let to_lib_info
     | Public (_, pkg) -> Package.version pkg
     | Installed_private | Installed | Private _ -> None
   in
+  let loc = conf.buildable.loc in
   let requires =
-    { Compilation_mode.By_mode.ocaml = conf.buildable.libraries
-    ; melange = conf.buildable.libraries
-    }
+    library_deps
+      ~loc
+      ~field:"melange.libraries"
+      ~modes
+      ~libs:conf.buildable.libraries
+      ~melange_libs:conf.buildable.melange_libraries
   in
   let parameters = conf.parameters in
   let allow_unused_libraries = conf.buildable.allow_unused_libraries in
-  let loc = conf.buildable.loc in
   let kind = conf.kind in
   let src_dir = dir in
   let orig_src_dir = None in

src/dune_rules/stanzas/parameter.ml

@@ -67,6 +67,7 @@ let decode =
        ; modules
        ; empty_module_interface_if_absent = false
        ; libraries
+       ; melange_libraries = None
        ; melange_modules = None
        ; foreign_archives = []
        ; extra_objects = Foreign.Objects.empty

test/blackbox-tests/test-cases/melange/conditional-libraries.t

@@ -0,0 +1,111 @@
+`melange.libraries` applies only to Melange compilation.
+
+The field is available starting in Dune 3.24.
+
+  $ mkdir old
+  $ cat > old/dune-project <<EOF
+  > (lang dune 3.23)
+  > (using melange 0.1)
+  > EOF
+  $ cat > old/dune <<EOF
+  > (library
+  >  (name old)
+  >  (modes melange)
+  >  (melange.libraries dep))
+  > EOF
+  $ dune build --root old
+  Entering directory 'old'
+  File "dune", line 4, characters 1-24:
+  4 |  (melange.libraries dep))
+       ^^^^^^^^^^^^^^^^^^^^^^^
+  Error: 'melange.libraries' is only available since version 3.24 of the dune
+  language. Please update your dune-project file to have (lang dune 3.24).
+  Leaving directory 'old'
+  [1]
+  $ rm -rf old
+
+  $ cat > dune-project <<EOF
+  > (lang dune 3.24)
+  > (using melange 0.1)
+  > EOF
+
+  $ mkdir lib_for_melange lib_for_native app
+  $ cat > lib_for_melange/dune <<EOF
+  > (library
+  >  (modes melange)
+  >  (name lib_for_melange))
+  > EOF
+  $ cat > lib_for_melange/foo.ml <<EOF
+  > let x = "lib for melange"
+  > EOF
+
+  $ cat > lib_for_native/dune <<EOF
+  > (library
+  >  (modes :standard)
+  >  (name lib_for_native))
+  > EOF
+  $ cat > lib_for_native/foo.ml <<EOF
+  > let x = "lib for native"
+  > EOF
+
+  $ cat > app/dune <<EOF
+  > (library
+  >  (modes melange :standard)
+  >  (name app)
+  >  (modules app common_intf)
+  >  (libraries lib_for_native)
+  >  (melange.libraries lib_for_melange))
+  > 
+  > (melange.emit
+  >  (target out)
+  >  (modules main)
+  >  (emit_stdlib false)
+  >  (libraries app))
+  > 
+  > (executable
+  >  (name main)
+  >  (modules main)
+  >  (libraries app))
+  > EOF
+
+  $ cat > app/common_intf.mli <<EOF
+  > val print : string -> unit
+  > EOF
+  $ cat > app/common_intf.ml <<EOF
+  > let message = Lib_for_native.Foo.x
+  > let print prefix = Format.eprintf "%s%s@." prefix message
+  > EOF
+  $ cat > app/common_intf.melange.ml <<EOF
+  > let message = Lib_for_melange.Foo.x
+  > let print prefix = Js.log2 prefix message
+  > EOF
+  $ cat > app/app.ml <<EOF
+  > let say_hello () = Common_intf.print "message: "
+  > EOF
+  $ cat > app/main.ml <<EOF
+  > let () = App.say_hello ()
+  > EOF
+
+  $ dune build @app/melange app/main.exe
+  $ node _build/default/app/out/app/main.js
+  message:  lib for melange
+  $ _build/default/app/main.exe
+  message: lib for native
+
+The field is rejected without Melange mode.
+
+  $ mkdir no-melange
+  $ cat > no-melange/dune <<EOF
+  > (library
+  >  (modes :standard)
+  >  (name no_melange)
+  >  (melange.libraries lib_for_melange))
+  > EOF
+  $ dune build no-melange
+  File "no-melange/dune", lines 1-4, characters 0-84:
+  1 | (library
+  2 |  (modes :standard)
+  3 |  (name no_melange)
+  4 |  (melange.libraries lib_for_melange))
+  Error: Cannot specify `melange.libraries' without `melange' mode
+  [1]