[App] Fix VSCode IDE debugger (#15747)

(cherry picked from commit 6714ca7)

src/lightning_app/CHANGELOG.md

@@ -18,6 +18,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ### Fixed
 
+- Fixed debugging with VSCode IDE ([#15747](https://github.com/Lightning-AI/lightning/pull/15747))
+
+
 - 
 
 

src/lightning_app/core/app.py

@@ -169,17 +169,17 @@ def __init__(
 
         logger.debug(f"ENV: {os.environ}")
 
-    def _update_index_file(self):
-        # update index.html,
-        # this should happen once for all apps before the ui server starts running.
-        frontend.update_index_file(FRONTEND_DIR, info=self.info, root_path=self.root_path)
-
         if _should_dispatch_app():
             os.environ["LIGHTNING_DISPATCHED"] = "1"
             from lightning_app.runners import MultiProcessRuntime
 
             MultiProcessRuntime(self).dispatch()
 
+    def _update_index_file(self):
+        # update index.html,
+        # this should happen once for all apps before the ui server starts running.
+        frontend.update_index_file(FRONTEND_DIR, info=self.info, root_path=self.root_path)
+
     def get_component_by_name(self, component_name: str):
         """Returns the instance corresponding to the given component name."""
         from lightning_app.structures import Dict as LightningDict