Properly construct File_keys when handling live errors requests

Summary: This is the same as the change made in D27577168 (a7e78a7), but at a different callsite

Reviewed By: mroch

Differential Revision: D27596742

fbshipit-source-id: 01c794904f41f27c8a5d43a784dae2bdbb6bc1bf

src/server/command_handler/commandHandler.ml

@@ -2159,7 +2159,10 @@ let handle_live_errors_request =
             let%lwt (live_errors, live_warnings) =
               match check_that_we_care_about_this_file ~options ~env ~file_path ~content with
               | Ok () ->
-                let file_key = File_key.SourceFile file_path in
+                let file_key =
+                  let file_options = Options.file_options options in
+                  Files.filename_from_string ~options:file_options file_path
+                in
                 let%lwt result =
                   Types_js.typecheck_contents ~options ~env ~profiling content file_key
                 in