[App] Improve debug triggering (#15951)

Author: tchaton

src/lightning_app/CHANGELOG.md

@@ -60,6 +60,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Fixed the `enable_spawn` method of the `WorkRunExecutor` ([#15812](https://github.com/Lightning-AI/lightning/pull/15812)
 
+
 - Fixed Sigterm Handler causing thread lock which caused KeyboardInterrupt to hang ([#15881](https://github.com/Lightning-AI/lightning/pull/15881))
 
 - Fixed a bug where using `L.app.structures` would cause multiple apps to be opened and fail with an error in the cloud ([#15911](https://github.com/Lightning-AI/lightning/pull/15911))
@@ -68,6 +69,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Fixed multiprocessing breakpoint ([#15950](https://github.com/Lightning-AI/lightning/pull/15950))
 
+- Fixed detection of a Lightning App running in debug mode ([#15951](https://github.com/Lightning-AI/lightning/pull/15951))
+
+
 ## [1.8.3] - 2022-11-22
 
 ### Changed

src/lightning_app/core/app.py

@@ -93,12 +93,10 @@ def __init__(
             >>> from lightning_app.runners import MultiProcessRuntime
             >>> class RootFlow(LightningFlow):
             ...     def run(self):
-            ...         print("Hello World!")
             ...         self._exit()
             ...
             >>> app = LightningApp(RootFlow())  # application can be dispatched using the `runners`.
             >>> MultiProcessRuntime(app).dispatch()
-            Hello World!
         """
 
         self.root_path = root_path  # when running behind a proxy

src/lightning_app/utilities/app_helpers.py

@@ -511,14 +511,10 @@ def is_static_method(klass_or_instance, attr) -> bool:
     return isinstance(inspect.getattr_static(klass_or_instance, attr), staticmethod)
 
 
-def _debugger_is_active() -> bool:
-    """Return if the debugger is currently active."""
-    return hasattr(sys, "gettrace") and sys.gettrace() is not None
-
-
 def _should_dispatch_app() -> bool:
     return (
-        _debugger_is_active()
+        __debug__
+        and "_pytest.doctest" not in sys.modules
         and not bool(int(os.getenv("LIGHTNING_DISPATCHED", "0")))
         and "LIGHTNING_APP_STATE_URL" not in os.environ
     )