Stop command palette Input message leakage (#3322)

* Fix Input event leakage from Command Palette to app

* Update the CHANGELOG

Author: davep

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Fixed the command palette crashing with a `TimeoutError` in any Python before 3.11 https://github.com/Textualize/textual/issues/3320
+- Fixed `Input` event leakage from `CommandPalette` to `App`.
 
 ## [0.37.0] - 2023-09-15
 

src/textual/command.py

@@ -876,6 +876,7 @@ def _input(self, event: Input.Changed) -> None:
         Args:
             event: The input event.
         """
+        event.stop()
         self.workers.cancel_all()
         search_value = event.value.strip()
         if search_value:
@@ -906,10 +907,14 @@ def _select_command(self, event: OptionList.OptionSelected) -> None:
 
     @on(Input.Submitted)
     @on(Button.Pressed)
-    def _select_or_command(self) -> None:
+    def _select_or_command(
+        self, event: Input.Submitted | Button.Pressed | None = None
+    ) -> None:
         """Depending on context, select or execute a command."""
         # If the list is visible, that means we're in "pick a command"
         # mode...
+        if event is not None:
+            event.stop()
         if self._list_visible:
             # ...so if nothing in the list is highlighted yet...
             if self.query_one(CommandList).highlighted is None: