Correct handling of existing MQTT subscriptions (#43056)

homeassistant/components/mqtt/subscription.py

@@ -29,6 +29,7 @@ class EntitySubscription:
     async def resubscribe_if_necessary(self, hass, other):
         """Re-subscribe to the new topic if necessary."""
         if not self._should_resubscribe(other):
+            self.unsubscribe_callback = other.unsubscribe_callback
             return
 
         if other is not None and other.unsubscribe_callback is not None:

tests/components/mqtt/test_subscription.py

@@ -160,21 +160,35 @@ async def test_qos_encoding_custom(hass, mqtt_mock, caplog):
 async def test_no_change(hass, mqtt_mock, caplog):
     """Test subscription to topics without change."""
 
+    calls = []
+
     @callback
-    def msg_callback(*args):
-        """Do nothing."""
-        pass
+    def record_calls(*args):
+        """Record calls."""
+        calls.append(args)
 
     sub_state = None
     sub_state = await async_subscribe_topics(
         hass,
         sub_state,
-        {"test_topic1": {"topic": "test-topic1", "msg_callback": msg_callback}},
+        {"test_topic1": {"topic": "test-topic1", "msg_callback": record_calls}},
     )
-    call_count = mqtt_mock.async_subscribe.call_count
+    subscribe_call_count = mqtt_mock.async_subscribe.call_count
+
+    async_fire_mqtt_message(hass, "test-topic1", "test-payload")
+    assert len(calls) == 1
+
     sub_state = await async_subscribe_topics(
         hass,
         sub_state,
-        {"test_topic1": {"topic": "test-topic1", "msg_callback": msg_callback}},
+        {"test_topic1": {"topic": "test-topic1", "msg_callback": record_calls}},
     )
-    assert call_count == mqtt_mock.async_subscribe.call_count
+    assert subscribe_call_count == mqtt_mock.async_subscribe.call_count
+
+    async_fire_mqtt_message(hass, "test-topic1", "test-payload")
+    assert len(calls) == 2
+
+    await async_unsubscribe_topics(hass, sub_state)
+
+    async_fire_mqtt_message(hass, "test-topic1", "test-payload")
+    assert len(calls) == 2