feature: warn if modules is missing any mentioned modules

We warn the user if modules_without_implementation, private_modules or
virtual_modules contains any modules not in the modules field.

Fixes #7026

This will be made into an error in 3.9.

Signed-off-by: Ali Caglayan <alizter@gmail.com>

Author: Alizter

CHANGES.md

@@ -20,6 +20,11 @@ Unreleased
 - Use `$PKG_CONFIG`, when set, to find the `pkg-config` binary  (#7469, fixes
   #2572, @anmonteiro)
 
+- Modules that were declared in `(modules_without_implementation)`,
+  `(private_modules)` or `(virtual_modules` but not declared in `(modules)` will
+  cause Dune to emit a warning which will become an error in 3.9. (#7608, fixes
+  #7026, @Alizter)
+
 - Preliminary support for Coq compiled intefaces (`.vos` files) enabled via
   `(mode vos)` in `coq.theory` stanzas. This can be used in combination with
   `dune coq top` to obtain fast re-building of dependencies (with no checking

src/dune_rules/modules_field_evaluator.ml

@@ -60,6 +60,9 @@ type single_module_error =
   | Vmodule_impl_missing_impl
   | Forbidden_new_public_module
   | Vmodule_impls_with_own_intf
+  | Undeclared_module_without_implementation
+  | Undeclared_private_module
+  | Undeclared_virtual_module
 
 type errors =
   { errors : (single_module_error * Loc.t * Module_name.Path.t) list
@@ -97,14 +100,19 @@ let find_errors ~modules ~intf_only ~virtual_modules ~private_modules
         in
         let ( ++ ) f g loc acc = f loc (g loc acc) in
         let ( !? ) = Option.is_some in
-        with_property private_ (add_if impl_vmodule Private_impl_of_vmodule)
+        with_property private_
+          (add_if impl_vmodule Private_impl_of_vmodule
+          ++ add_if (not !?modules) Undeclared_private_module)
         @@ with_property intf_only
              (add_if has_impl Spurious_module_intf
-             ++ add_if impl_vmodule Vmodule_impl_intf_only_exclusion)
+             ++ add_if impl_vmodule Vmodule_impl_intf_only_exclusion
+             ++ add_if (not !?modules) Undeclared_module_without_implementation
+             )
         @@ with_property virtual_
              (add_if has_impl Spurious_module_virtual
              ++ add_if !?intf_only Virt_intf_overlap
-             ++ add_if !?private_ Private_virt_module)
+             ++ add_if !?private_ Private_virt_module
+             ++ add_if (not !?modules) Undeclared_virtual_module)
         @@ with_property modules
              (add_if
                 ((not !?private_)
@@ -154,18 +162,24 @@ let check_invalid_module_listing ~stanza_loc ~modules_without_implementation
     let missing_intf_only = get Missing_intf_only in
     let spurious_modules_intf = get Spurious_module_intf in
     let spurious_modules_virtual = get Spurious_module_virtual in
+    let undeclared_modules_without_implementation =
+      get Undeclared_module_without_implementation
+    in
+    let undeclared_private_modules = get Undeclared_private_module in
+    let undeclared_virtual_modules = get Undeclared_virtual_module in
     let uncapitalized =
       List.map ~f:(fun (_, m) -> Module_name.Path.uncapitalize m)
     in
     let line_list modules =
       Pp.enumerate modules ~f:(fun (_, m) ->
           Pp.verbatim (Module_name.Path.to_string m))
     in
-    let print before l after =
+    let print ?(is_error = true) before l after =
       match l with
       | [] -> ()
       | (loc, _) :: _ ->
-        User_error.raise ~loc (List.concat [ before; [ line_list l ]; after ])
+        User_warning.emit ~is_error ~loc
+          (List.concat [ before; [ line_list l ]; after ])
     in
     print
       [ Pp.text "The following modules are implementations of virtual modules:"
@@ -213,6 +227,18 @@ let check_invalid_module_listing ~stanza_loc ~modules_without_implementation
       (unimplemented_virt_modules |> Module_name.Path.Set.to_list
       |> List.map ~f:(fun name -> (stanza_loc, name)))
       [ Pp.text "You must provide an implementation for all of these modules." ];
+    (* Checking that (modules) incldues all declared modules *)
+    let print_undelared_modules field mods =
+      (* TODO: this is a warning for now, change to an error in 3.9 *)
+      print ~is_error:false
+        [ Pp.textf "These modules appear in the %s field:" field ]
+        mods
+        [ Pp.text "They must also appear in the modules field." ]
+    in
+    print_undelared_modules "modules_without_implementation"
+      undeclared_modules_without_implementation;
+    print_undelared_modules "private_modules" undeclared_private_modules;
+    print_undelared_modules "virtual_modules" undeclared_virtual_modules;
     (if missing_intf_only <> [] then
      match Ordered_set_lang.loc modules_without_implementation with
      | None ->
@@ -337,4 +363,5 @@ let eval ~modules:(all_modules : Module.Source.t Module_trie.t) ~stanza_loc
     eval ~modules:all_modules ~stanza_loc ~private_modules ~kind ~src_dir
       settings eval0
   in
+  (* Check that modules without implementation are a subset of the modules field *)
   (eval0.modules, modules)

test/blackbox-tests/test-cases/intf-only/excluded-by-modules-field.t

@@ -19,6 +19,12 @@ field
   > EOF
 
   $ dune build --display short
+  File "dune", line 4, characters 33-34:
+  4 |  (modules_without_implementation x)
+                                       ^
+  Warning: These modules appear in the modules_without_implementation field:
+  - X
+  They must also appear in the module field.
         ocamlc .foo.objs/byte/y.{cmi,cmo,cmt} (exit 2)
   File "y.ml", line 1, characters 16-17:
   1 | module type F = X

test/blackbox-tests/test-cases/private-modules/private-module-excluded-by-modules-field.t

@@ -24,6 +24,12 @@ modules:
 X is silently ignored:
 
   $ dune build
+  File "dune", line 5, characters 18-19:
+  5 |  (private_modules x))
+                        ^
+  Warning: These modules appear in the private_modules field:
+  - X
+  They must also appear in the module field.
   File "y.ml", line 1, characters 9-14:
   1 | let () = X.foo ()
                ^^^^^

test/blackbox-tests/test-cases/virtual-libraries/virtual-modules-excluded-by-modules-field.t

@@ -26,6 +26,12 @@ Specifying a virtual module that isn't inside the (modules ..) field:
   $ touch impl/x.ml
 
   $ dune build --display short
+  File "dune", line 4, characters 18-19:
+  4 |  (virtual_modules x)
+                        ^
+  Warning: These modules appear in the virtual_modules field:
+  - X
+  They must also appear in the module field.
       ocamldep impl/.impl.objs/x.impl.d
         ocamlc .foo.objs/byte/y.{cmi,cmo,cmt} (exit 2)
   File "y.ml", line 1, characters 16-17: