Target hints: only load targets from subdir

bin/print_rules.ml

@@ -119,7 +119,7 @@ let term =
           let* request =
             match targets with
             | [] ->
-              Load_rules.all_direct_targets ()
+              Load_rules.all_direct_targets None
               >>| Path.Build.Map.foldi ~init:[] ~f:(fun p _ acc ->
                       Path.build p :: acc)
               >>| Action_builder.paths

bin/target.ml

@@ -20,18 +20,23 @@ let request targets =
       | Alias a -> Alias.request a)
 
 let target_hint (_setup : Dune_rules.Main.build_system) path =
-  assert (Path.is_managed path);
   let open Memo.O in
   let sub_dir = Option.value ~default:path (Path.parent path) in
-  (* CR-someday amokhov: There are two issues with the code below.
+  (* CR-someday amokhov:
 
-     (1) We first get *all* targets but then filter out only those that are
-     defined in the [sub_dir]. It would be better to just get the targets for
-     the [sub_dir] directly (the API supports this).
-
-     (2) We currently provide the same hint for all targets. It would be nice to
+     We currently provide the same hint for all targets. It would be nice to
      indicate whether a hint corresponds to a file or to a directory target. *)
-  let+ candidates = Load_rules.all_direct_targets () >>| Path.Build.Map.keys in
+  let root =
+    match sub_dir with
+    | External e ->
+      Code_error.raise "target_hint: external path"
+        [ ("path", Path.External.to_dyn e) ]
+    | In_source_tree d -> d
+    | In_build_dir d -> Path.Build.drop_build_context_exn d
+  in
+  let+ candidates =
+    Load_rules.all_direct_targets (Some root) >>| Path.Build.Map.keys
+  in
   let candidates =
     if Path.is_in_build_dir path then List.map ~f:Path.build candidates
     else

src/dune_engine/load_rules.ml

@@ -918,8 +918,11 @@ end
 module Source_tree_map_reduce =
   Source_tree.Dir.Make_map_reduce (Memo) (All_targets)
 
-let all_direct_targets () =
-  let* root = Source_tree.root ()
+let all_direct_targets dir =
+  let* root =
+    match dir with
+    | None -> Source_tree.root ()
+    | Some dir -> Source_tree.nearest_dir dir
   and* contexts = Memo.Lazy.force (Build_config.get ()).contexts in
   Memo.parallel_map (Context_name.Map.values contexts) ~f:(fun ctx ->
       Source_tree_map_reduce.map_reduce root ~traverse:Sub_dirs.Status.Set.all

src/dune_engine/load_rules.mli

@@ -69,8 +69,12 @@ val is_target : Path.t -> is_target Memo.t
 val is_under_directory_target : Path.t -> bool Memo.t
 
 (** List of all buildable direct targets. This does not include files and
-    directory produced under a directory target. *)
-val all_direct_targets : unit -> target_type Path.Build.Map.t Memo.t
+    directories produced under a directory target.
+
+    If argument is [None], load the root, otherwise only load targets from the
+    nearest subdirectory. *)
+val all_direct_targets :
+  Path.Source.t option -> target_type Path.Build.Map.t Memo.t
 
 type rule_or_source =
   | Source of Digest.t