test: virtual_modules with incompatible kind

Signed-off-by: Shon Feder <[email protected]>

Author: shonfeder

src/dune_rules/stanzas/library.ml

@@ -125,19 +125,18 @@ let decode =
            ~since_expanded:Stanza_common.Modules_settings.since_expanded
            "virtual_modules"
        in
-       let+ kind_loc, dune_file_kind =
-         located
-         @@ field "kind" Lib_kind.Dune_file.decode ~default:Lib_kind.Dune_file.Normal
+       let+ dune_file_kind =
+         field "kind" Lib_kind.Dune_file.decode ~default:Lib_kind.Dune_file.Normal
        in
        let kind : Lib_kind.t =
          match virtual_modules, dune_file_kind with
          | Some _, ((Parameter | Ppx_deriver _ | Ppx_rewriter _) as incompatable_kind) ->
            User_error.raise
-             ~loc:kind_loc
+             ~loc:stanza_loc
              ~hints:[ Pp.text "Remove either the 'kind' or 'virtual_modules' fields" ]
              [ Pp.text "Only virtual libraries can have 'virtual_modules'"
              ; Pp.textf
-                 "but this library has 'virtual_modules' and is specified as kind %s "
+                 "but this library has 'virtual_modules' and is specified as kind '%s'."
                  (Lib_kind.Dune_file.cstr_name incompatable_kind)
              ]
          | Some _, Normal ->

test/blackbox-tests/test-cases/virtual-libraries/invalid-kind.t

@@ -0,0 +1,22 @@
+Test that trying to use virtual_modules with an incompatible kind reports a user
+error
+
+  $ echo "(lang dune 3.20)" > dune-project
+
+  $ touch empty.mli
+  $ cat >dune <<EOF
+  > (library
+  >  (name invalid_lib)
+  >  (kind parameter)
+  >  (virtual_modules empty))
+  > EOF
+  $ dune build
+  File "dune", lines 1-4, characters 0-72:
+  1 | (library
+  2 |  (name invalid_lib)
+  3 |  (kind parameter)
+  4 |  (virtual_modules empty))
+  Error: Only virtual libraries can have 'virtual_modules'
+  but this library has 'virtual_modules' and is specified as kind 'parameter'.
+  Hint: Remove either the 'kind' or 'virtual_modules' fields
+  [1]