reflect reviewer's comments - neat & opt

Signed-off-by: Haochen Kotoi-Xie <hx@kxc.inc>

src/dune_rules/melange/melange_rules.ml

@@ -172,17 +172,19 @@ let build_js ~loc ~dir ~pkg_name ~mode ~module_systems ~output ~obj_dir ~sctx
            ; Dep src
            ]))
 
-(** attach [deps] to the specified [alias] AND the (dune default) [all] alias.
+(* attach [deps] to the specified [alias] AND the (dune default) [all] alias.
 
-    when [alias] is not supplied, {!Melange_stanzas.Emit.implicit_alias} is
-    assumed. *)
+   when [alias] is not supplied, {!Melange_stanzas.Emit.implicit_alias} is
+   assumed. *)
 let add_deps_to_aliases ?(alias = Melange_stanzas.Emit.implicit_alias) ~dir deps
     =
   let open Memo.O in
   let alias = Alias.make alias ~dir in
   let dune_default_alias = Alias.all ~dir in
   let attach alias = Rules.Produce.Alias.add_deps alias deps in
-  attach alias >>> attach dune_default_alias
+  let+ () = attach alias
+  and+ () = attach dune_default_alias in
+  ()
 
 let setup_emit_cmj_rules ~sctx ~dir ~scope ~expander ~dir_contents
     (mel : Melange_stanzas.Emit.t) =

test/blackbox-tests/test-cases/melange/aliases.t

@@ -48,10 +48,12 @@ Dune default alias works
   $ cat > dune <<EOF
   > (melange.emit
   >  (target output)
-  >  (modules main))
+  >  (modules main)
+  >  (emit_stdlib false))
   > (melange.emit
   >  (target output2)
-  >  (modules main2))
+  >  (modules main2)
+  >  (emit_stdlib false))
   > EOF
 
   $ cat > main2.ml <<EOF
@@ -97,6 +99,7 @@ Even if user defines an alias, dune default alias should still work
   > (melange.emit
   >  (target output)
   >  (modules main)
+  >  (emit_stdlib false)
   >  (alias foo))
   > EOF