Support for using oxcaml 0.1 in workspace files

doc/changes/added/13395.md

@@ -0,0 +1,2 @@
+- Allow enabling extensions with `(using ..)` in `dune-workspace` files
+  (#13395, @spiessimon)

src/dune_lang/dune_project.ml

@@ -222,6 +222,8 @@ include Versioned_file.Make (struct
     type t = Stanza.Parser.t list
   end)
 
+let workspace_instance ~syntax ~version = { Lang.Instance.syntax; version; data = [] }
+
 let default_dune_language_version =
   ref (Syntax.greatest_supported_version_exn Stanza.syntax)
 ;;
@@ -321,29 +323,54 @@ module Extension = struct
          | Deleted_in _ -> acc
          | Extension e -> Not_selected e :: acc))
   ;;
+
+  let explicit_extensions_map explicit_extensions =
+    match
+      String.Map.of_list
+        (List.map explicit_extensions ~f:(fun (e : instance) ->
+           let syntax =
+             let (Packed e) = e.extension in
+             e.syntax
+           in
+           Syntax.name syntax, e))
+    with
+    | Error (name, _, ext) ->
+      User_error.raise
+        ~loc:ext.loc
+        [ Pp.textf "Extension %S specified for the second time." name ]
+    | Ok map -> map
+  ;;
+
+  let parse_extensions ~lang_version =
+    let open Decoder in
+    let* explicit_extensions =
+      multi_field
+        "using"
+        (let+ loc = loc
+         and+ name = located string
+         and+ ver = located Syntax.Version.decode
+         and+ parse_args = capture in
+         (* We don't parse the arguments quite yet as we want to set the
+          version of extensions before parsing them. *)
+         instantiate ~dune_lang_ver:lang_version ~loc ~parse_args name ver)
+    in
+    String_with_vars.set_decoding_env
+      (let extensions =
+         List.map explicit_extensions ~f:(fun (instance : instance) ->
+           let (Packed { syntax; _ }) = instance.extension in
+           syntax, instance.version)
+       in
+       Pform.Env.initial ~stanza:lang_version ~extensions)
+    @@
+    let explicit_extensions_map = explicit_extensions_map explicit_extensions in
+    return (explicit_extensions_map, explicit_extensions)
+  ;;
 end
 
 module Melange_syntax = struct
   let name = "melange"
 end
 
-let explicit_extensions_map explicit_extensions =
-  match
-    String.Map.of_list
-      (List.map explicit_extensions ~f:(fun (e : Extension.instance) ->
-         let syntax =
-           let (Packed e) = e.extension in
-           e.syntax
-         in
-         Syntax.name syntax, e))
-  with
-  | Error (name, _, ext) ->
-    User_error.raise
-      ~loc:ext.loc
-      [ Pp.textf "Extension %S specified for the second time." name ]
-  | Ok map -> map
-;;
-
 let make_parsing_context ~(lang : Lang.Instance.t) extensions =
   let init =
     let init = Univ_map.singleton (Syntax.key lang.syntax) (Active lang.version) in
@@ -382,6 +409,7 @@ let make_parsing_context ~(lang : Lang.Instance.t) extensions =
 ;;
 
 let interpret_lang_and_extensions ~(lang : Lang.Instance.t) ~explicit_extensions =
+  let explicit_extensions = Extension.explicit_extensions_map explicit_extensions in
   let extensions = Extension.automatic ~explicitly_selected:explicit_extensions in
   let parsing_context = make_parsing_context ~lang extensions in
   let extension_args, extension_stanzas =
@@ -520,7 +548,7 @@ let infer ~dir info packages =
   let lang = get_dune_lang () in
   let name = default_name ~dir ~packages in
   let parsing_context, stanza_parser, extension_args =
-    interpret_lang_and_extensions ~lang ~explicit_extensions:String.Map.empty
+    interpret_lang_and_extensions ~lang ~explicit_extensions:[]
   in
   let implicit_transitive_deps = Implicit_transitive_deps.Stanza.default ~lang in
   let wrapped_executables = wrapped_executables_default ~lang in
@@ -885,26 +913,9 @@ let parse ~dir ~(lang : Lang.Instance.t) ~file =
   let open Decoder in
   fields
   @@
-  let* explicit_extensions =
-    multi_field
-      "using"
-      (let+ loc = loc
-       and+ name = located string
-       and+ ver = located Syntax.Version.decode
-       and+ parse_args = capture in
-       (* We don't parse the arguments quite yet as we want to set the
-          version of extensions before parsing them. *)
-       Extension.instantiate ~dune_lang_ver:lang.version ~loc ~parse_args name ver)
+  let* explicit_extensions_map, explicit_extensions =
+    Extension.parse_extensions ~lang_version:lang.version
   in
-  String_with_vars.set_decoding_env
-    (let extensions =
-       List.map explicit_extensions ~f:(fun (instance : Extension.instance) ->
-         let (Extension.Packed { syntax; _ }) = instance.extension in
-         syntax, instance.version)
-     in
-     Pform.Env.initial ~stanza:lang.version ~extensions)
-  @@
-  let explicit_extensions = explicit_extensions_map explicit_extensions in
   let parsing_context, stanza_parser, extension_args =
     interpret_lang_and_extensions ~lang ~explicit_extensions
   in
@@ -1040,7 +1051,7 @@ let parse ~dir ~(lang : Lang.Instance.t) ~file =
     let root = dir in
     let dialects =
       let dialects =
-        match String.Map.find explicit_extensions Melange_syntax.name with
+        match String.Map.find explicit_extensions_map Melange_syntax.name with
         | Some extension -> (extension.loc, Dialect.rescript) :: dialects
         | None -> dialects
       in

src/dune_lang/dune_project.mli

@@ -50,8 +50,14 @@ module Lang : sig
       what stanzas the user can write in [dune] files. *)
 
   val register : Syntax.t -> Stanza.Parser.t list -> unit
+
+  module Instance : sig
+    type t
+  end
 end
 
+val workspace_instance : syntax:Syntax.t -> version:Syntax.Version.t -> Lang.Instance.t
+
 module Extension : sig
   type 'a t
 
@@ -76,8 +82,22 @@ module Extension : sig
 
   (** Register experimental extensions that were deleted *)
   val register_deleted : name:string -> deleted_in:Syntax.Version.t -> unit
+
+  (** An instantiated extension with captured arguments *)
+  type instance
+
+  val parse_extensions
+    :  lang_version:Syntax.Version.t
+    -> (instance String.Map.t * instance list) Decoder.fields_parser
 end
 
+(** Interpret extensions and build parsing context. Returns the parsing context,
+    stanza parser, and extension arguments. *)
+val interpret_lang_and_extensions
+  :  lang:Lang.Instance.t
+  -> explicit_extensions:Extension.instance list
+  -> Univ_map.t * Stanza.t list Decoder.t * Univ_map.t
+
 (** Create an anonymous project at the given directory
 
     Optional arguments:

src/dune_sexp/syntax.ml

@@ -319,8 +319,8 @@ module Error = struct
     User_error.raise
       ~loc
       ([ Pp.textf
-           "%s is available only when %s is enabled in the dune-project file. You must \
-            enable it using (using %s %s) in your dune-project file."
+           "%s is available only when %s is enabled in the dune-project or workspace \
+            file. You must enable it using (using %s %s) in the file."
            what
            t.name
            t.name

src/source/workspace.ml

@@ -794,6 +794,8 @@ let find_lock_dir t path =
 
 let add_repo t repo = { t with repos = repo :: t.repos }
 
+(* Why do we even have a separate versioned file here if we're using the same
+   syntax as the dune project? *)
 include Dune_lang.Versioned_file.Make (struct
     type t = unit
   end)
@@ -979,7 +981,7 @@ let check_lock_dirs_no_dupes lock_dirs =
       ]
 ;;
 
-let step1 clflags =
+let step1 ~(lang : Lang.Instance.t) clflags =
   let { Clflags.x
       ; profile = cl_profile
       ; instrument_with = cl_instrument_with
@@ -1009,6 +1011,19 @@ let step1 clflags =
     let+ x = field in
     lazy (Option.value cl ~default:(Lazy.force x))
   in
+  (* This is all dodgy but we get away with it because we don't really allow
+     extensions to inject their own stanza into the workspace. *)
+  let* parsing_context, _stanza_parser, _extension_args =
+    let+ _, explicit_extensions =
+      Dune_project.Extension.parse_extensions ~lang_version:lang.version
+    in
+    let lang =
+      Dune_project.workspace_instance ~syntax:lang.syntax ~version:lang.version
+    in
+    Dune_lang.Dune_project.interpret_lang_and_extensions ~lang ~explicit_extensions
+  in
+  Dune_lang.Decoder.set_many parsing_context
+  @@
   let* () = Dune_lang.Versioned_file.no_more_lang
   and+ env = env_field_lazy
   and+ profile =
@@ -1111,7 +1126,7 @@ let step1 clflags =
   { Step1.t; config }
 ;;
 
-let step1 clflags = fields (step1 clflags)
+let step1 ~lang clflags = fields (step1 ~lang clflags)
 
 let default clflags =
   let { Clflags.x
@@ -1157,7 +1172,7 @@ let load_step1 clflags p =
       parse_contents lb ~f:(fun lang ->
         String_with_vars.set_decoding_env
           (Pform.Env.initial ~stanza:lang.version ~extensions:[])
-          (step1 clflags)))
+          (step1 ~lang clflags)))
 ;;
 
 let filename = "dune-workspace"

test/blackbox-tests/test-cases/extensions-versioning/using-and-dune-lang.t/run.t

@@ -4,8 +4,8 @@ at the current language version:
   File "dune", line 1, characters 0-5:
   1 | (mdx)
       ^^^^^
-  Error: 'mdx' is available only when mdx is enabled in the dune-project file.
-  You must enable it using (using mdx ..) in your dune-project file.
+  Error: 'mdx' is available only when mdx is enabled in the dune-project or
+  workspace file. You must enable it using (using mdx ..) in the file.
   Note however that the currently selected version of dune (1.0) does not
   support this plugin. The first version of this plugin is 0.1 and was
   introduced in dune 2.4.

test/blackbox-tests/test-cases/foreign-stubs/fs-mode-dependent/fsmd-exe.t/run.t

@@ -10,8 +10,8 @@ Without the toggle, we get an error message for using the new mode subfield
   11 |    (mode native)
           ^^^^^^^^^^^^^
   Error: 'mode' is available only when mode_specific_stubs is enabled in the
-  dune-project file. You must enable it using (using mode_specific_stubs 0.1)
-  in your dune-project file.
+  dune-project or workspace file. You must enable it using (using
+  mode_specific_stubs 0.1) in the file.
 
 But the toggle only exists in Dune 3.5
   $ cat >dune-project <<EOF

test/blackbox-tests/test-cases/github1529.t/run.t

@@ -11,5 +11,5 @@ file is present.
   1 | (menhir (modules parser))
       ^^^^^^^^^^^^^^^^^^^^^^^^^
   Error: 'menhir' is available only when menhir is enabled in the dune-project
-  file. You must enable it using (using menhir <version>) in your dune-project file.
+  or workspace file. You must enable it using (using menhir <version>) in the file.
   [1]

test/blackbox-tests/test-cases/mdx-stanza/using-mdx.t/run.t

@@ -7,6 +7,6 @@ dune-project
   File "dune", line 1, characters 0-5:
   1 | (mdx)
       ^^^^^
-  Error: 'mdx' is available only when mdx is enabled in the dune-project file.
-  You must enable it using (using mdx 0.1) in your dune-project file.
+  Error: 'mdx' is available only when mdx is enabled in the dune-project or
+  workspace file. You must enable it using (using mdx 0.1) in the file.
   [1]

test/blackbox-tests/test-cases/menhir/flags-in-workspace.t

@@ -13,9 +13,9 @@ See #9024.
   > EOF
 
   $ dune build 2>&1 | head -n 5
-  Internal error, please report upstream including the contents of _build/log.
-  Description:
-    ("Syntax identifier is unset",
-     { name = "menhir"
-     ; supported_versions =
+  File "dune-workspace", line 3, characters 7-29:
+  3 |  (test (menhir_flags --table)))
+             ^^^^^^^^^^^^^^^^^^^^^^
+  Error: 'menhir_flags' is available only when menhir is enabled in the
+  dune-project or workspace file. You must enable it using (using menhir 2.1)
   [1]

test/blackbox-tests/test-cases/oxcaml/library-field-parameters.t

@@ -21,8 +21,8 @@ It should fail because the syntax extension wasn't enabled in `dune-project`:
   1 | (library (name lib) (parameters a))
                           ^^^^^^^^^^^^^^
   Error: 'parameters' is available only when oxcaml is enabled in the
-  dune-project file. You must enable it using (using oxcaml 0.1) in your
-  dune-project file.
+  dune-project or workspace file. You must enable it using (using oxcaml 0.1)
+  in the file.
   Note however that oxcaml is experimental and might change without notice in
   the future.
   [1]

test/blackbox-tests/test-cases/oxcaml/library_parameter.t

@@ -25,8 +25,8 @@ The test build should fails because the oxcaml extension is not available.
   2 |  (public_name param.intf)
   3 |  (name param_intf))
   Error: 'library_parameter' is available only when oxcaml is enabled in the
-  dune-project file. You must enable it using (using oxcaml 0.1) in your
-  dune-project file.
+  dune-project or workspace file. You must enable it using (using oxcaml 0.1)
+  in the file.
   Note however that oxcaml is experimental and might change without notice in
   the future.
   [1]