melange: don't emit module group wrapper as a JS file in melange.emit (#11987)

* melange: don't emit module group wrapper as a JS file in `melange.emit`

Signed-off-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>

* add changelog entry

Signed-off-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>

---------

Signed-off-by: Antonio Nuno Monteiro <anmonteiro@gmail.com>

Author: anmonteiro

doc/changes/11987.md

@@ -0,0 +1,3 @@
+- Stop emitting empty module group wrapper `.js` file in `melange.emit`
+  (#11987, fixes #11986, @anmonteiro)
+

src/dune_rules/melange/melange_rules.ml

@@ -176,7 +176,7 @@ let js_targets_of_modules modules ~module_systems ~output =
   List.map module_systems ~f:(fun (_, js_ext) ->
     modules
     |> Modules.With_vlib.drop_vlib
-    |> Modules.fold ~init:Path.Set.empty ~f:(fun m acc ->
+    |> Modules.fold_user_available ~init:Path.Set.empty ~f:(fun m acc ->
       if Module.has m ~ml_kind:Impl
       then (
         let target = Path.build @@ make_js_name ~js_ext ~output m in
@@ -479,7 +479,7 @@ let modules_for_js_and_obj_dir ~sctx ~dir_contents ~scope (mel : Melange_stanzas
   in
   let+ modules = modules_in_obj_dir ~sctx ~scope ~preprocess:mel.preprocess modules in
   let modules_for_js =
-    Modules.fold modules ~init:[] ~f:(fun x acc ->
+    Modules.fold_user_available modules ~init:[] ~f:(fun x acc ->
       if Module.has x ~ml_kind:Impl then x :: acc else acc)
   in
   modules, modules_for_js, obj_dir

test/blackbox-tests/test-cases/melange/depend-on-installed.t

@@ -100,6 +100,4 @@ Test dependency on installed package
           melc dist/node_modules/b/b.js
           melc dist/node_modules/b/bar.js
           melc dist/node_modules/b/foo.js
-          melc .dist.mobjs/melange/melange.{cmi,cmj,cmt}
-          melc dist/.dist.mobjs/melange.js
   Leaving directory 'app'

test/blackbox-tests/test-cases/melange/empty-entries-target-dir-exists.t

@@ -24,11 +24,10 @@ If there's more than 1 module, we currently emit the module group wrapper,
   > EOF
 
   $ dune build @dist --display=short 2>&1 | grep 'melange\.js'
-          melc dist/.dist.mobjs/melange.js
+  [1]
   $ ls -a _build/default/dist
   .
   ..
-  .dist.mobjs
   x.js
   y.js
 

test/blackbox-tests/test-cases/melange/melange-wrapper-module.t

@@ -35,7 +35,7 @@ is relative to the artifact, not the dune file)
   5 |  (promote (into ../../foo))
                       ^^^^^^^^^
   Error: Directory "app/dist/foo" does not exist. Please create it manually.
-  -> required by _build/default/app/dist/app/.dist.mobjs/melange.js
+  -> required by _build/default/app/dist/app/other/other.js
   -> required by alias app/dist
   [1]
 

test/blackbox-tests/test-cases/melange/promote-with-into.t

@@ -37,13 +37,4 @@ Test interaction of melange.emit library ppx dependencies
   -> required by melange target dist
   -> required by alias lib/test/all
   -> required by alias default
-  File "lib/impl/dune", line 5, characters 18-29:
-  5 |  (preprocess (pps not-present)))
-                        ^^^^^^^^^^^
-  Error: Library "not-present" not found.
-  -> required by melange target dist
-  -> required by library "mel-subdir" in _build/default/lib/impl
-  -> required by _build/default/lib/test/dist/lib/test/.dist.mobjs/melange.js
-  -> required by alias lib/test/all
-  -> required by alias default
   [1]

test/blackbox-tests/test-cases/melange/transitive-ppx.t

@@ -25,8 +25,4 @@ Building a project with 2 melange.emit stanzas should add rules to both aliases
   > EOF
 
   $ dune build @mel --display=short
-          melc .dist.mobjs/melange/melange.{cmi,cmj,cmt}
-          melc dist/.dist.mobjs/melange.js
   $ dune build @second --display=short
-          melc .dist-es6.mobjs/melange/melange.{cmi,cmj,cmt}
-          melc dist-es6/.dist-es6.mobjs/melange.mjs