fix: regression in 11200 (#11204)

Remove all error checking for empty projects in [$ dune subst]

Signed-off-by: Rudi Grinberg <[email protected]>

bin/subst.ml

@@ -332,6 +332,10 @@ let subst vcs =
                  |> Memo.return)
        in
        Some (None, None, Path.Source.Set.to_list files))
+  >>| Option.bind ~f:(fun ((_, _, files) as s) ->
+    match files with
+    | [] -> None
+    | _ :: _ -> Some s)
   >>= Memo.Option.iter ~f:(fun (version, commit, files) ->
     let+ (dune_project : Dune_project.t) =
       (* CR-soon rgrinberg: unify this check with the above version check *)

doc/changes/11204.md

@@ -0,0 +1,2 @@
+- Remove useless error message when running `$ dune subst` in empty projects.
+  (@rgrinberg, #11204, fixes #11200)

test/blackbox-tests/test-cases/github11200.t

@@ -2,8 +2,3 @@ Running `dune subst` should succeed in an empty directory.
 Regression test for https://github.com/ocaml/dune/issues/11200
 
   $ dune subst
-  File ".", line 1, characters 0-0:
-  Error: There is no dune-project file in the current directory, please add one
-  with a (name <name>) field in it.
-  Hint: 'dune subst' must be executed from the root of the project.
-  [1]