Ensure mqtt subscriptions are in a set (#122201)

homeassistant/components/mqtt/__init__.py

@@ -254,7 +254,7 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
             mqtt_data.client.async_restore_tracked_subscriptions(
                 mqtt_data.subscriptions_to_restore
             )
-            mqtt_data.subscriptions_to_restore = []
+            mqtt_data.subscriptions_to_restore = set()
         mqtt_data.reload_dispatchers.append(
             entry.add_update_listener(_async_config_entry_updated)
         )

homeassistant/components/mqtt/client.py

@@ -427,12 +427,12 @@ class MQTT:
         await self.async_init_client()
 
     @property
-    def subscriptions(self) -> list[Subscription]:
+    def subscriptions(self) -> set[Subscription]:
         """Return the tracked subscriptions."""
-        return [
+        return {
             *chain.from_iterable(self._simple_subscriptions.values()),
             *self._wildcard_subscriptions,
-        ]
+        }
 
     def cleanup(self) -> None:
         """Clean up listeners."""
@@ -735,7 +735,7 @@ class MQTT:
 
     @callback
     def async_restore_tracked_subscriptions(
-        self, subscriptions: list[Subscription]
+        self, subscriptions: set[Subscription]
     ) -> None:
         """Restore tracked subscriptions after reload."""
         for subscription in subscriptions:

homeassistant/components/mqtt/models.py

@@ -423,7 +423,7 @@ class MqttData:
     reload_handlers: dict[str, CALLBACK_TYPE] = field(default_factory=dict)
     reload_schema: dict[str, VolSchemaType] = field(default_factory=dict)
     state_write_requests: EntityTopicState = field(default_factory=EntityTopicState)
-    subscriptions_to_restore: list[Subscription] = field(default_factory=list)
+    subscriptions_to_restore: set[Subscription] = field(default_factory=set)
     tags: dict[str, dict[str, MQTTTagScanner]] = field(default_factory=dict)