feature: multiple alias support in rules

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

ps-id: 7f58c532-3611-4290-b07c-9ad973f2a995
Signed-off-by: Ali Caglayan <[email protected]>

src/dune_rules/dune_file.ml

@@ -1476,7 +1476,7 @@ module Rule = struct
     ; locks : Locks.t
     ; loc : Loc.t
     ; enabled_if : Blang.t
-    ; alias : Alias.Name.t option
+    ; aliases : Alias.Name.t list
     ; package : Package.t option
     }
 
@@ -1528,7 +1528,7 @@ module Rule = struct
     ; locks = []
     ; loc
     ; enabled_if = Blang.true_
-    ; alias = None
+    ; aliases = []
     ; package = None
     }
 
@@ -1574,9 +1574,13 @@ module Rule = struct
          field_o "package"
            (Dune_lang.Syntax.since Stanza.syntax (2, 0)
            >>> Stanza_common.Pkg.decode)
-       and+ alias =
-         field_o "alias"
-           (Dune_lang.Syntax.since Stanza.syntax (2, 0) >>> Alias.Name.decode)
+       and+ aliases =
+         field "alias" ~default:[]
+           (repeat Alias.Name.decode >>= function
+            | [] as l -> return l
+            | [ _ ] as l ->
+              Dune_lang.Syntax.since Stanza.syntax (2, 0) >>> return l
+            | l -> Dune_lang.Syntax.since Stanza.syntax (3, 5) >>> return l)
        in
        let mode, patch_back_source_tree =
          match mode with
@@ -1602,7 +1606,7 @@ module Rule = struct
        ; locks
        ; loc
        ; enabled_if
-       ; alias
+       ; aliases
        ; package
        ; patch_back_source_tree
        })
@@ -1672,7 +1676,7 @@ module Rule = struct
         ; locks = []
         ; loc
         ; enabled_if
-        ; alias = None
+        ; aliases = []
         ; package = None
         })
 
@@ -1702,7 +1706,7 @@ module Rule = struct
         ; locks = []
         ; loc
         ; enabled_if
-        ; alias = None
+        ; aliases = []
         ; package = None
         })
 end

src/dune_rules/dune_file.mli

@@ -292,7 +292,7 @@ module Rule : sig
     ; locks : Locks.t
     ; loc : Loc.t
     ; enabled_if : Blang.t
-    ; alias : Alias.Name.t option
+    ; aliases : Alias.Name.t list
     ; package : Package.t option
     }
 end

src/dune_rules/simple_rules.ml

@@ -10,6 +10,12 @@ module Alias_rules = struct
   let add_empty sctx ~loc ~alias =
     let action = Action_builder.return (Action.Full.make Action.empty) in
     add sctx ~loc ~alias action
+
+  let add_list sctx ~aliases ~loc build =
+    Memo.parallel_iter aliases ~f:(fun alias -> add sctx ~alias ~loc build)
+
+  let add_list_empty sctx ~loc ~aliases =
+    Memo.parallel_iter aliases ~f:(fun alias -> add_empty sctx ~loc ~alias)
 end
 
 let check_filename =
@@ -37,17 +43,17 @@ let check_filename =
     | Dir p -> not_in_dir ~kind ~error_loc (Path.to_string p)
 
 type rule_kind =
-  | Alias_only of Alias.Name.t
-  | Alias_with_targets of Alias.Name.t * Path.Build.t
+  | Aliases_only of Alias.Name.t list
+  | Aliases_with_targets of Alias.Name.t list * Path.Build.t
   | No_alias
 
 let rule_kind ~(rule : Rule.t) ~(action : _ Action_builder.With_targets.t) =
-  match rule.alias with
-  | None -> No_alias
-  | Some alias -> (
+  match rule.aliases with
+  | [] -> No_alias
+  | aliases -> (
     match Targets.head action.targets with
-    | None -> Alias_only alias
-    | Some target -> Alias_with_targets (alias, target))
+    | None -> Aliases_only aliases
+    | Some target -> Aliases_with_targets (aliases, target))
 
 let interpret_and_add_locks ~expander locks action =
   let+ locks = Expander.expand_locks expander ~base:`Of_expander locks in
@@ -66,13 +72,10 @@ let add_user_rule sctx ~dir ~(rule : Rule.t)
 
 let user_rule sctx ?extra_bindings ~dir ~expander (rule : Rule.t) =
   Expander.eval_blang expander rule.enabled_if >>= function
-  | false -> (
-    match rule.alias with
-    | None -> Memo.return None
-    | Some name ->
-      let alias = Alias.make ~dir name in
-      let+ () = Alias_rules.add_empty sctx ~alias ~loc:(Some rule.loc) in
-      None)
+  | false ->
+    let aliases = List.map rule.aliases ~f:(Alias.make ~dir) in
+    let+ () = Alias_rules.add_list_empty sctx ~aliases ~loc:(Some rule.loc) in
+    None
   | true -> (
     let* targets =
       match rule.targets with
@@ -120,18 +123,21 @@ let user_rule sctx ?extra_bindings ~dir ~expander (rule : Rule.t) =
     | No_alias ->
       let+ targets = add_user_rule sctx ~dir ~rule ~action ~expander in
       Some targets
-    | Alias_with_targets (alias, alias_target) ->
+    | Aliases_with_targets (aliases, alias_target) ->
       let* () =
-        let alias = Alias.make alias ~dir in
-        Rules.Produce.Alias.add_deps alias
-          (Action_builder.path (Path.build alias_target))
+        let aliases = List.map ~f:(Alias.make ~dir) aliases in
+        Memo.parallel_iter aliases ~f:(fun alias ->
+            Rules.Produce.Alias.add_deps alias
+              (Action_builder.path (Path.build alias_target)))
       in
       let+ targets = add_user_rule sctx ~dir ~rule ~action ~expander in
       Some targets
-    | Alias_only name ->
-      let alias = Alias.make ~dir name in
+    | Aliases_only aliases ->
+      let aliases = List.map ~f:(Alias.make ~dir) aliases in
       let* action = interpret_and_add_locks ~expander rule.locks action.build in
-      let+ () = Alias_rules.add sctx ~alias ~loc:(Some rule.loc) action in
+      let+ () =
+        Alias_rules.add_list sctx ~aliases ~loc:(Some rule.loc) action
+      in
       None)
 
 let copy_files sctx ~dir ~expander ~src_dir (def : Copy_files.t) =

src/dune_rules/simple_rules.mli

@@ -13,6 +13,19 @@ module Alias_rules : sig
 
   val add_empty :
     Super_context.t -> loc:Stdune.Loc.t option -> alias:Alias.t -> unit Memo.t
+
+  val add_list :
+       Super_context.t
+    -> aliases:Alias.t list
+    -> loc:Loc.t option
+    -> Action.Full.t Action_builder.t
+    -> unit Memo.t
+
+  val add_list_empty :
+       Super_context.t
+    -> loc:Stdune.Loc.t option
+    -> aliases:Alias.t list
+    -> unit Memo.t
 end
 
 (** Interpret a [(rule ...)] stanza and return the targets it produces, if any. *)

src/dune_rules/test_rules.ml

@@ -105,7 +105,7 @@ let rules (t : Dune_file.Tests.t) ~sctx ~dir ~scope ~expander ~dir_contents =
                 ; locks = t.locks
                 ; loc
                 ; enabled_if = t.enabled_if
-                ; alias = None
+                ; aliases = []
                 ; package = t.package
                 }
               in

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

@@ -0,0 +1,53 @@
+Testing multiple aliases in rules stanza
+
+First we start with a dune-project before alias was introduced:
+  $ cat > dune-project << EOF
+  > (lang dune 1.9)
+  > EOF
+
+  $ cat > dune << EOF
+  > (rule
+  > (alias a)
+  > (action (echo "I have run")))
+  > EOF
+
+  $ dune build @a
+  File "dune", line 2, characters 0-9:
+  2 | (alias a)
+      ^^^^^^^^^
+  Error: 'alias' is only available since version 2.0 of the dune language.
+  Please update your dune-project file to have (lang dune 2.0).
+  [1]
+
+Next we update the dune-project file to use dune 2.0:
+  $ cat > dune-project << EOF
+  > (lang dune 2.0)
+  > EOF
+
+  $ dune build @a
+  I have run
+
+We now update the dune file to use multiple aliases
+  $ cat > dune << EOF
+  > (rule
+  > (alias a b)
+  > (action (echo "I have run")))
+  > EOF
+
+  $ dune build @a @b
+  File "dune", line 2, characters 0-11:
+  2 | (alias a b)
+      ^^^^^^^^^^^
+  Error: 'alias' is only available since version 3.5 of the dune language.
+  Please update your dune-project file to have (lang dune 3.5).
+  [1]
+
+Updating the dune-project file to use dune 3.5 allows the build to succeed:
+  $ cat > dune-project << EOF
+  > (lang dune 3.5)
+  > EOF
+
+  $ dune build @a
+  I have run
+  $ dune build @b
+  I have run