Add Alias.add_{stamp,action}_dep

These functions will be useful to construct alias elsewhere

src/alias.ml

@@ -184,3 +184,19 @@ let rules store =
                         (Path.Set.elements deps))))
     in
     rule :: acc)
+
+let add_stamp_dep (store: Store.t) (t : t) ~data =
+  let digest = Digest.string (Sexp.to_string data) in
+  let digest_path = file_with_digest_suffix t ~digest in
+  add_deps store t [digest_path];
+  digest_path
+
+let add_action_dep (store: Store.t) (t : t) ~action ~action_deps =
+  let data =
+    let deps = Sexp.To_sexp.list Jbuild.Dep_conf.sexp_of_t action_deps in
+    let action =
+      match action with
+      | None -> Sexp.Atom "none"
+      | Some a -> List [Atom "some"; Action.Unexpanded.sexp_of_t a] in
+    Sexp.List [deps ; action] in
+  add_stamp_dep store t ~data

src/alias.mli

@@ -70,3 +70,21 @@ end
 val add_deps : Store.t -> t -> Path.t list -> unit
 
 val rules : Store.t -> Build_interpret.Rule.t list
+
+(** Create an alias dependency for an action and its inputs represented by
+    [~data]. The path returned is the file that should be represented by the
+    file the action will create following execution.*)
+val add_stamp_dep
+  : Store.t
+  -> t
+  -> data:Sexp.t
+  -> Path.t
+
+(** Like [add_stamp_dep] but an action (if present) and the dependencies can be
+    passed in directly. *)
+val add_action_dep
+  : Store.t
+  -> t
+  -> action:Action.Unexpanded.t option
+  -> action_deps:Jbuild.Dep_conf.t list
+  -> Path.t

src/gen_rules.ml

@@ -570,21 +570,11 @@ module Gen(P : Params) = struct
          ~scope)
 
   let alias_rules (alias_conf : Alias_conf.t) ~dir ~scope =
-    let digest =
-      let deps =
-        Sexp.To_sexp.list Dep_conf.sexp_of_t alias_conf.deps in
-      let action =
-        match alias_conf.action with
-        | None -> Sexp.Atom "none"
-        | Some a -> List [Atom "some" ; Action.Unexpanded.sexp_of_t a]
-      in
-      Sexp.List [deps ; action]
-      |> Sexp.to_string
-      |> Digest.string
-    in
     let alias = Alias.make alias_conf.name ~dir in
-    let digest_path = Alias.file_with_digest_suffix alias ~digest in
-    Alias.add_deps (SC.aliases sctx) alias [digest_path];
+    let digest_path =
+      Alias.add_action_dep (SC.aliases sctx) alias
+        ~action:alias_conf.action
+        ~action_deps:alias_conf.deps in
     let deps = SC.Deps.interpret sctx ~scope ~dir alias_conf.deps in
     SC.add_rule sctx
       ~locks:(interpret_locks ~dir ~scope alias_conf.locks)