fed-prims: Phase G — file-list-dir (Sys.readdir, sorted, native-safe)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

hosts/ocaml/bin/run_tests.ml

@@ -1486,6 +1486,33 @@ let run_foundation_tests () =
   assert_eq "rsa non-string args" (Bool false)
     (call "rsa-sha256-verify" [Integer 1; Integer 2; Integer 3]);
 
+  Printf.printf "\nSuite: file-list-dir\n";
+  let expect_err nm f =
+    (try ignore (f ());
+       incr fail_count; Printf.printf "  FAIL: %s — no error\n" nm
+     with Eval_error _ ->
+       incr pass_count; Printf.printf "  PASS: %s\n" nm
+        | _ ->
+       incr fail_count; Printf.printf "  FAIL: %s — wrong exn\n" nm)
+  in
+  let tmp = Filename.temp_file "fld" "" in
+  Sys.remove tmp; Unix.mkdir tmp 0o755;
+  let touch n = let oc = open_out (Filename.concat tmp n) in close_out oc in
+  touch "b.txt"; touch "a.txt"; touch "c.txt";
+  assert_eq "file-list-dir sorted"
+    (List [String "a.txt"; String "b.txt"; String "c.txt"])
+    (call "file-list-dir" [String tmp]);
+  expect_err "file-list-dir missing"
+    (fun () -> call "file-list-dir" [String (Filename.concat tmp "nope")]);
+  expect_err "file-list-dir not-a-dir"
+    (fun () -> call "file-list-dir" [String (Filename.concat tmp "a.txt")]);
+  expect_err "file-list-dir arity"
+    (fun () -> call "file-list-dir" []);
+  (* best-effort cleanup *)
+  (try List.iter (fun n -> Sys.remove (Filename.concat tmp n))
+         ["a.txt"; "b.txt"; "c.txt"]; Unix.rmdir tmp
+   with _ -> ());
+
   Printf.printf "\nSuite: vm-extension-dispatch\n";
   let make_bc op = ({
     vc_arity = 0; vc_rest_arity = -1; vc_locals = 0;

hosts/ocaml/lib/sx_primitives.ml

@@ -3237,6 +3237,21 @@ let () =
       with Sys_error msg -> raise (Eval_error ("file-read: " ^ msg)))
     | _ -> raise (Eval_error "file-read: (path)"));
 
+  (* fed-sx Step 3 segment replay. Sorted names, no "."/".." ;
+     errors prefixed like file-read (msg carries enoent/enotdir). *)
+  register "file-list-dir" (fun args ->
+    match args with
+    | [String path] ->
+      (try
+        let names = Sys.readdir path in
+        let names =
+          Array.to_list names
+          |> List.filter (fun n -> n <> "." && n <> "..") in
+        let names = List.sort compare names in
+        List (List.map (fun n -> String n) names)
+      with Sys_error msg -> raise (Eval_error ("file-list-dir: " ^ msg)))
+    | _ -> raise (Eval_error "file-list-dir: (path)"));
+
   register "file-write" (fun args ->
     match args with
     | [String path; String content] ->