fix(connection-selection): normalize connection string before caching in _persist_and_cache_connection

Strip whitespace and validate length before updating _connection_history_cache,
ensuring the in-memory cache always holds the same normalized value that was
persisted. Prevents blank/duplicate entries from surfacing in the combobox and
being re-sent as preserved_connections on periodic port refresh.

Author: amilcarlucas

ardupilot_methodic_configurator/backend_filesystem_program_settings.py

@@ -648,7 +648,7 @@ def get_connection_history() -> list[str]:
         return ProgramSettings._connection_history.get_items(settings)
 
     @staticmethod
-    def store_connection(connection_string: str) -> None:
+    def store_connection(connection_string: str) -> Optional[str]:
         """
         Save a new connection string to history.
 
@@ -660,14 +660,16 @@ def store_connection(connection_string: str) -> None:
         Args:
             connection_string: The connection string to store (max 200 characters).
 
-        Raises:
-            ValueError: If connection string is invalid (logged as warning, not raised)
+        Returns:
+            The normalized connection string that was stored, or None if invalid.
 
         """
         try:
             settings = ProgramSettings._get_settings_as_dict()
             settings = ProgramSettings._connection_history.store_item(connection_string, settings)
             ProgramSettings._set_settings_from_dict(settings)
+            return ProgramSettings._connection_history.normalizer(connection_string)
         except ValueError as e:
             # Log validation errors but don't raise (backward compatible behavior)
             logging_warning("Failed to store connection string to history: %s", e)
+            return None

ardupilot_methodic_configurator/frontend_tkinter_connection_selection.py

@@ -124,11 +124,12 @@ def __init__(  # pylint: disable=too-many-arguments, too-many-positional-argumen
 
     def _persist_and_cache_connection(self, connection_string: str) -> None:
         """Persist a connection string to settings and update the in-memory history cache."""
-        ProgramSettings.store_connection(connection_string)
-        # Update cache in-memory (most-recent-first, deduplicated) to avoid a disk re-read.
-        self._connection_history_cache = [connection_string] + [
-            c for c in self._connection_history_cache if c != connection_string
-        ]
+        normalized = ProgramSettings.store_connection(connection_string)
+        if normalized is None:
+            return
+        # Update cache in-memory (most-recent-first, deduplicated) using the normalized value
+        # to avoid a disk re-read and to keep the cache consistent with what was persisted.
+        self._connection_history_cache = [normalized] + [c for c in self._connection_history_cache if c != normalized]
 
     def start_periodic_refresh(self) -> None:
         """Start periodic refresh of available ports every 3 seconds."""