fix: Allow anonymous actions to be directly attached to multiple aliases

doc/changes/fixed/15581.md

@@ -0,0 +1,4 @@
+- Fix a target-less rule attached to multiple aliases (`(rule (aliases a b)
+  ...)`) leaking unrelated contributions between those aliases. Building one
+  alias no longer pulls in actions or dependencies that were added only to
+  another of the rule's aliases. (#15581, @NatKarmios)

src/dune_engine/build_system.ml

@@ -256,7 +256,7 @@ module Internal = struct
 
   (* The current version of the rule digest scheme. We should increment it when
      making any changes to the scheme, to avoid collisions. *)
-  let rule_digest_version = 29
+  let rule_digest_version = 30
 
   let compute_rule_digest
         (rule : Rule.t)
@@ -735,14 +735,21 @@ module Internal = struct
       in
       let d = Digest.to_string digest in
       let basename =
-        match act.alias with
-        | None -> d
-        | Some a -> Alias.Name.to_string a ^ "-" ^ d
+        match act.aliases with
+        | [] -> d
+        | aliases ->
+          let a =
+            aliases
+            |> List.map ~f:Alias.Name.to_string
+            |> List.min ~f:String.compare
+            |> Option.value_exn
+          in
+          a ^ "-" ^ d
       in
       Path.Build.relative dir basename
     in
     let rule =
-      let { Rule.Anonymous_action.action = _; loc; dir = _; alias = _ } = act in
+      let { Rule.Anonymous_action.action = _; loc; dir = _; aliases = _ } = act in
       Rule.make
         ~info:(if Loc.is_none loc then Internal else From_dune_file loc)
         ~targets:(Targets.File.create target)
@@ -754,7 +761,7 @@ module Internal = struct
         rule
         ~rule_kind:
           (Anonymous_action
-             { attached_to_alias = Option.is_some act.alias
+             { attached_to_alias = List.is_non_empty act.aliases
              ; capture_stdout
              ; stamp_file = target
              })
@@ -796,7 +803,7 @@ module Internal = struct
               { action; env; locks; can_go_in_shared_cache; sandbox; corrections }
           ; loc = _
           ; dir
-          ; alias
+          ; aliases
           }
         =
         act
@@ -817,10 +824,12 @@ module Internal = struct
         Action.digest d action;
         digest_locks d locks;
         Digest.Manual.string d (Path.Build.to_string dir);
-        Digest.Manual.option
-          d
-          ~f:(fun d alias -> Digest.Manual.string d (Alias.Name.to_string alias))
-          alias;
+        let alias_names =
+          aliases
+          |> List.map ~f:Alias.Name.to_string
+          |> List.sort_uniq ~compare:String.compare
+        in
+        Digest.Manual.list d ~f:Digest.Manual.string alias_names;
         Digest.Manual.bool d capture_stdout;
         Digest.Manual.bool d can_go_in_shared_cache;
         digest_sandbox_config d sandbox;

src/dune_engine/rule.ml

@@ -139,6 +139,6 @@ module Anonymous_action = struct
     { action : Action.Full.t
     ; loc : Loc.t
     ; dir : Path.Build.t
-    ; alias : Alias.Name.t option
+    ; aliases : Alias.Name.t list
     }
 end

src/dune_engine/rule.mli

@@ -88,6 +88,7 @@ module Anonymous_action : sig
     ; dir : Path.Build.t
       (** Directory the action is attached to. This is the directory where
         the outcome of the action will be cached. *)
-    ; alias : Alias.Name.t option (** For better error messages *)
+    ; aliases : Alias.Name.t list
+      (** The aliases this action is attached to. For better error messages. *)
     }
 end

src/dune_engine/rules.ml

@@ -150,20 +150,29 @@ module Produce = struct
         }
     ;;
 
-    let add_action t ~loc action =
+    (* All aliases in [ts] are expected to share a directory: the shared
+       anonymous action is created in the representative's directory. *)
+    let add_action ts ~loc action =
+      let representative =
+        match ts with
+        | [] -> Code_error.raise "Rules.Produce.Alias.add_action: empty list" []
+        | r :: _ -> r
+      in
       let action =
         let open Action_builder.O in
-        let+ action = action in
+        let+ action in
         { Rule.Anonymous_action.action
         ; loc
-        ; dir = Alias.dir t
-        ; alias = Some (Alias.name t)
+        ; dir = Alias.dir representative
+        ; aliases = List.map ts ~f:Alias.name
         }
       in
-      alias
-        t
-        { expansions = Appendable_list.singleton (loc, Dir_rules.Alias_spec.Action action)
-        }
+      Memo.parallel_iter ts ~f:(fun t ->
+        alias
+          t
+          { expansions =
+              Appendable_list.singleton (loc, Dir_rules.Alias_spec.Action action)
+          })
     ;;
   end
 end

src/dune_engine/rules.mli

@@ -72,9 +72,9 @@ module Produce : sig
         [alias]. *)
     val add_deps : t -> ?loc:Stdune.Loc.t -> unit Action_builder.t -> unit Memo.t
 
-    (** [add_action alias ~loc action] arrange things so that [action]
-        is executed as part of the build of alias [alias]. *)
-    val add_action : t -> loc:Loc.t -> Action.Full.t Action_builder.t -> unit Memo.t
+    (** [add_action aliases ~loc action] arrange things so that [action]
+        is executed as part of the build of aliases [aliases]. *)
+    val add_action : t list -> loc:Loc.t -> Action.Full.t Action_builder.t -> unit Memo.t
   end
 end
 

src/dune_rules/cc_flags.ml

@@ -169,7 +169,7 @@ let cc_vendor_action (ctx : Build_context.t) =
       |> Action.Full.make
       |> Action.Full.add_env env
     in
-    { Rule.Anonymous_action.action; loc = Loc.none; dir = ctx.build_dir; alias = None }
+    { Rule.Anonymous_action.action; loc = Loc.none; dir = ctx.build_dir; aliases = [] }
 ;;
 
 let check_warn = function

src/dune_rules/cinaps.ml

@@ -276,7 +276,7 @@ let gen_rules sctx t ~dir ~scope =
               ])
       |> Action.Full.add_env env
     in
-    Super_context.add_alias_action sctx ~dir ~loc cinaps_alias action
+    Super_context.add_alias_action sctx ~dir ~loc [ cinaps_alias ] action
   in
   match t.alias with
   | Some _ -> Memo.return ()

src/dune_rules/cram/cram_rules.ml

@@ -89,7 +89,7 @@ let test_rule
     (* We error out on invalid tests even if they are disabled. *)
     let* () = add_extra_aliases_deps () in
     Action_builder.fail { fail = (fun () -> missing_run_t test) }
-    |> Alias_rules.add sctx ~alias ~loc
+    |> Alias_rules.add sctx ~aliases:[ alias ] ~loc
   | Ok test ->
     (* enabled_if controls whether this test is included in @runtest (and other aliases),
        but the test can always be run explicitly via its own alias. *)
@@ -160,7 +160,7 @@ let test_rule
       |> Action_builder.with_file_targets ~file_targets:[ output ]
       |> Super_context.add_rule sctx ~dir ~loc
     in
-    Alias_rules.add sctx ~alias ~loc
+    Alias_rules.add sctx ~aliases:[ alias ] ~loc
     @@
     let open Action_builder.O in
     let+ () = List.map ~f:Path.build [ script; output ] |> Action_builder.paths in

src/dune_rules/dep_rules.ml

@@ -98,7 +98,7 @@ let merge_deps ~dir ~transitive ~immediate =
         |> Action.Full.make ~sandbox:Sandbox_config.no_sandboxing
     ; loc = Loc.none
     ; dir
-    ; alias = None
+    ; aliases = []
     }
   in
   Build_system.execute_action_stdout action |> Action_builder.of_memo

src/dune_rules/format_rules.ml

@@ -21,7 +21,7 @@ let formatter_diff_action =
       { Rule.Anonymous_action.action
       ; loc
       ; dir = Alias.dir alias
-      ; alias = Some (Alias.name alias)
+      ; aliases = [ Alias.name alias ]
       }
     in
     Build_system.dep_on_alias_definition (Rules.Dir_rules.Alias_spec.Action action)

src/dune_rules/inline_tests.ml

@@ -431,7 +431,7 @@ include Sub_system.Register_end_point (struct
           sctx
           ~dir
           ~loc:info.loc
-          alias
+          [ alias ]
           (let open Action_builder.O in
            let promotion_targets =
              List.concat_map source_modules ~f:Module.sources_without_pp
@@ -479,7 +479,7 @@ include Sub_system.Register_end_point (struct
       | true -> gen_rules c ~expander ~info ~backends
       | false ->
         let alias = Alias.make Alias0.runtest ~dir in
-        Simple_rules.Alias_rules.add_empty sctx ~alias ~loc:info.loc
+        Simple_rules.Alias_rules.add_empty sctx ~aliases:[ alias ] ~loc:info.loc
     ;;
   end)
 

src/dune_rules/mdx.ml

@@ -401,7 +401,7 @@ let gen_rules_for_single_file stanza ~sctx ~dir ~expander ~mdx_prog ~mdx_prog_ge
   in
   Super_context.add_alias_action
     sctx
-    (Alias.make Alias0.runtest ~dir)
+    [ Alias.make Alias0.runtest ~dir ]
     mdx_action
     ~loc
     ~dir

src/dune_rules/ocamldep.ml

@@ -78,7 +78,7 @@ let ocamldep_action ~sandbox ~sctx ~dir ~ml_kind unit =
       ; Dep (Module.File.path source)
       ]
   in
-  { Rule.Anonymous_action.action; loc = Loc.none; dir; alias = None }
+  { Rule.Anonymous_action.action; loc = Loc.none; dir; aliases = [] }
 ;;
 
 (* Top-level cache per (source path, ml_kind). Without it, each caller's

src/dune_rules/ocamlobjinfo.mll

@@ -78,7 +78,7 @@ let rules (ocaml : Ocaml_toolchain.t) ~dir ~sandbox ~units =
     { Rule.Anonymous_action.action
     ; loc = Loc.none
     ; dir
-    ; alias = None
+    ; aliases = []
     }
   in
   Dune_engine.Build_system.execute_action_stdout action
@@ -97,7 +97,7 @@ let archive_rules (ocaml : Ocaml_toolchain.t) ~dir ~sandbox ~archive =
     { Rule.Anonymous_action.action
     ; loc = Loc.none
     ; dir
-    ; alias = None
+    ; aliases = []
     }
   in
   Dune_engine.Build_system.execute_action_stdout action

src/dune_rules/opam_create.ml

@@ -454,7 +454,7 @@ let add_alias_rule (ctx : Build_context.t) ~profile ~project ~pkg =
     match Package.has_opam_file pkg with
     | Generated_with_diff when not use_source_opam ->
       Rules.Produce.Alias.add_action
-        opam_alias
+        [ opam_alias ]
         ~loc:(Loc.in_file source_opam_path)
         (let open Action_builder.O in
          let+ () = Action_builder.path (Path.build generated_opam_path)

src/dune_rules/pp_spec_rules.ml

@@ -151,7 +151,7 @@ let driver_flags expander ~corrected_suffix ~driver_flags ~standard =
 let lint_module sctx ~sandbox ~dir ~expander ~lint ~lib_name ~scope =
   let open Action_builder.O in
   let add_alias build =
-    Super_context.add_alias_action sctx (Alias.make Alias0.lint ~dir) build ~dir
+    Super_context.add_alias_action sctx [ Alias.make Alias0.lint ~dir ] build ~dir
   in
   let lint =
     Module_name.Per_item.map lint ~f:(function

src/dune_rules/rocq/rocq_rules.ml

@@ -820,11 +820,10 @@ let setup_output_diff_rule ~loc ~dir ~sctx ~rocq_lang_version ~rocq_sources rocq
       ; directory_diffs = true
       }
     in
-    let alias = Alias.make ~dir Alias0.runtest in
     Simple_rules.Alias_rules.add
       sctx
       ~loc
-      ~alias
+      ~aliases:[ Alias.make ~dir Alias0.runtest ]
       (let open Action_builder.O in
        let+ () = Action_builder.paths [ diff.file1; Path.build diff.file2 ] in
        Action.Full.make (Action.Diff diff))

src/dune_rules/simple_rules.ml

@@ -15,15 +15,19 @@ module Alias_rules = struct
       else Memo.return ()
   ;;
 
-  let add sctx ~alias ~loc build =
-    let dir = Alias.dir alias in
-    check_empty ~loc ~dir alias
-    >>> Super_context.add_alias_action sctx alias ~dir ~loc build
+  let add sctx ~aliases ~loc build =
+    match aliases with
+    | [] -> Code_error.raise "Alias_rules.add: empty list of aliases" []
+    | representative :: _ ->
+      let dir = Alias.dir representative in
+      Memo.parallel_iter aliases ~f:(fun alias ->
+        check_empty ~loc ~dir:(Alias.dir alias) alias)
+      >>> Super_context.add_alias_action sctx aliases ~dir ~loc build
   ;;
 
-  let add_empty sctx ~loc ~alias =
+  let add_empty sctx ~loc ~aliases =
     let action = Action_builder.return (Action.Full.make Action.empty) in
-    add sctx ~loc ~alias action
+    add sctx ~loc ~aliases action
   ;;
 end
 
@@ -138,7 +142,7 @@ let user_rule sctx ~dir ~expander (rule : Rule_conf.t) =
     let+ () =
       Memo.parallel_iter rule.aliases ~f:(fun alias ->
         let alias = Alias.make ~dir alias in
-        Alias_rules.add_empty sctx ~loc:rule.loc ~alias)
+        Alias_rules.add_empty sctx ~loc:rule.loc ~aliases:[ alias ])
     in
     None
   | true ->
@@ -203,14 +207,9 @@ let user_rule sctx ~dir ~expander (rule : Rule_conf.t) =
        let+ () =
          match List.map ~f:(Alias.make ~dir) aliases with
          | [] -> Code_error.raise "empty list of aliases" []
-         | alias :: extra_aliases ->
-           let loc = rule.loc in
+         | aliases ->
            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)
+           |> Alias_rules.add sctx ~aliases ~loc:rule.loc
        in
        None)
 ;;
@@ -341,7 +340,7 @@ let alias sctx ~dir ~expander (alias_conf : Alias_conf.t) =
   Alias_rules.check_empty ~loc ~dir alias
   >>> Expander.eval_blang expander alias_conf.enabled_if
   >>= function
-  | false -> Alias_rules.add_empty sctx ~loc ~alias
+  | false -> Alias_rules.add_empty sctx ~loc ~aliases:[ alias ]
   | true ->
     (match alias_conf.action with
      | None ->
@@ -369,5 +368,5 @@ let alias sctx ~dir ~expander (alias_conf : Alias_conf.t) =
            ~what:"aliases"
        in
        interpret_and_add_locks ~expander alias_conf.locks action
-       |> Alias_rules.add sctx ~loc ~alias)
+       |> Alias_rules.add sctx ~loc ~aliases:[ alias ])
 ;;

src/dune_rules/simple_rules.mli

@@ -5,12 +5,16 @@ open Import
 module Alias_rules : sig
   val add
     :  Super_context.t
-    -> alias:Alias.t
+    -> aliases:Alias.t list
     -> loc:Loc.t
     -> Action.Full.t Action_builder.t
     -> unit Memo.t
 
-  val add_empty : Super_context.t -> loc:Stdune.Loc.t -> alias:Alias.t -> unit Memo.t
+  val add_empty
+    :  Super_context.t
+    -> loc:Stdune.Loc.t
+    -> aliases:Alias.t list
+    -> unit Memo.t
 end
 
 (** Interpret a [(rule ...)] stanza and return the targets it produces, if any. *)

src/dune_rules/super_context.ml

@@ -160,7 +160,7 @@ let extend_action_env t ~dir action =
 let execute_action_stdout t ?alias ~loc ~dir action =
   let open Action_builder.O in
   (let+ action = extend_action_env t ~dir action in
-   { Rule.Anonymous_action.action; loc; dir; alias })
+   { Rule.Anonymous_action.action; loc; dir; aliases = Option.to_list alias })
   |> Build_system.execute_action_stdout
 ;;
 
@@ -190,9 +190,9 @@ let add_rule_get_targets t ?mode ?loc ~dir build =
 
 let add_rules t ?loc ~dir builds = Memo.parallel_iter builds ~f:(add_rule ?loc t ~dir)
 
-let add_alias_action t alias ~dir ~loc action =
+let add_alias_action t aliases ~dir ~loc action =
   let build = extend_action t action ~dir in
-  Rules.Produce.Alias.add_action alias ~loc build
+  Rules.Produce.Alias.add_action aliases ~loc build
 ;;
 
 let resolve_program_memo t ~dir ?where ?hint ~loc bin =

src/dune_rules/super_context.mli

@@ -53,7 +53,7 @@ val add_rules
 
 val add_alias_action
   :  t
-  -> Alias.t
+  -> Alias.t list
   -> dir:Path.Build.t
   -> loc:Loc.t
   -> Action.Full.t Action_builder.t