fix: user rules with multiple aliases generate single action

Signed-off-by: Ali Caglayan <[email protected]>

Author: Alizter

src/dune_rules/simple_rules.ml

@@ -131,10 +131,16 @@ let user_rule sctx ?extra_bindings ~dir ~expander (rule : Rule_conf.t) =
        Some targets
      | Aliases_only aliases ->
        let+ () =
-         let action = interpret_and_add_locks ~expander rule.locks action.build in
-         Memo.parallel_iter aliases ~f:(fun alias ->
-           let alias = Alias.make ~dir alias in
-           Alias_rules.add sctx ~alias ~loc:rule.loc action)
+         match List.map ~f:(Alias.make ~dir) aliases with
+         | [] -> Code_error.raise "empty list of aliases" []
+         | alias :: extra_aliases ->
+           let loc = rule.loc in
+           interpret_and_add_locks ~expander rule.locks action.build
+           |> Alias_rules.add sctx ~alias ~loc
+           >>> Memo.parallel_iter extra_aliases ~f:(fun extra_alias ->
+             Dep.alias alias
+             |> Action_builder.dep
+             |> Rules.Produce.Alias.add_deps ~loc extra_alias)
        in
        None)
 ;;

test/blackbox-tests/test-cases/alias-multiple.t

@@ -64,7 +64,6 @@ Updating the dune-project file to use dune 3.5 allows the build to succeed:
   $ dune build @a
   I have run
   $ dune build @b
-  I have run
 
 Also note having both the alias and aliases fields in the same rule stanza is
 not allowed
@@ -112,7 +111,6 @@ Building both aliases at the same time should only run the action once
   $ dune clean
   $ dune build @a @b
   I have run
-  I have run
 
 A similar test with a rule that produces a target
   $ cat > dune << EOF