Avoid generating matchers that will never be used in MQTT (#118068)

homeassistant/components/mqtt/client.py

@@ -238,12 +238,13 @@ def subscribe(
     return remove
 
 
-@dataclass(frozen=True)
+@dataclass(slots=True, frozen=True)
 class Subscription:
     """Class to hold data about an active subscription."""
 
     topic: str
-    matcher: Any
+    is_simple_match: bool
+    complex_matcher: Callable[[str], bool] | None
     job: HassJob[[ReceiveMessage], Coroutine[Any, Any, None] | None]
     qos: int = 0
     encoding: str | None = "utf-8"
@@ -312,11 +313,6 @@ class MqttClientSetup:
         return self._client
 
 
-def _is_simple_match(topic: str) -> bool:
-    """Return if a topic is a simple match."""
-    return not ("+" in topic or "#" in topic)
-
-
 class EnsureJobAfterCooldown:
     """Ensure a cool down period before executing a job.
 
@@ -788,7 +784,7 @@ class MQTT:
 
         The caller is responsible clearing the cache of _matching_subscriptions.
         """
-        if _is_simple_match(subscription.topic):
+        if subscription.is_simple_match:
             self._simple_subscriptions.setdefault(subscription.topic, []).append(
                 subscription
             )
@@ -805,7 +801,7 @@ class MQTT:
         """
         topic = subscription.topic
         try:
-            if _is_simple_match(topic):
+            if subscription.is_simple_match:
                 simple_subscriptions = self._simple_subscriptions
                 simple_subscriptions[topic].remove(subscription)
                 if not simple_subscriptions[topic]:
@@ -846,8 +842,11 @@ class MQTT:
         if not isinstance(topic, str):
             raise HomeAssistantError("Topic needs to be a string!")
 
+        is_simple_match = not ("+" in topic or "#" in topic)
+        matcher = None if is_simple_match else _matcher_for_topic(topic)
+
         subscription = Subscription(
-            topic, _matcher_for_topic(topic), HassJob(msg_callback), qos, encoding
+            topic, is_simple_match, matcher, HassJob(msg_callback), qos, encoding
         )
         self._async_track_subscription(subscription)
         self._matching_subscriptions.cache_clear()
@@ -1053,7 +1052,9 @@ class MQTT:
         subscriptions.extend(
             subscription
             for subscription in self._wildcard_subscriptions
-            if subscription.matcher(topic)
+            # mypy doesn't know that complex_matcher is always set when
+            # is_simple_match is False
+            if subscription.complex_matcher(topic)  # type: ignore[misc]
         )
         return subscriptions
 
@@ -1241,7 +1242,7 @@ def _raise_on_error(result_code: int) -> None:
         raise HomeAssistantError(f"Error talking to MQTT: {message}")
 
 
-def _matcher_for_topic(subscription: str) -> Any:
+def _matcher_for_topic(subscription: str) -> Callable[[str], bool]:
     # pylint: disable-next=import-outside-toplevel
     from paho.mqtt.matcher import MQTTMatcher