Fix race when unsubscribing from MQTT topics (#67376)

* Fix race when unsubscribing from MQTT topics

* Improve test

homeassistant/components/mqtt/__init__.py

@@ -967,10 +967,6 @@ class MQTT:
             self.subscriptions.remove(subscription)
             self._matching_subscriptions.cache_clear()
 
-            if any(other.topic == topic for other in self.subscriptions):
-                # Other subscriptions on topic remaining - don't unsubscribe.
-                return
-
             # Only unsubscribe if currently connected.
             if self.connected:
                 self.hass.async_create_task(self._async_unsubscribe(topic))
@@ -982,6 +978,10 @@ class MQTT:
 
         This method is a coroutine.
         """
+        if any(other.topic == topic for other in self.subscriptions):
+            # Other subscriptions on topic remaining - don't unsubscribe.
+            return
+
         async with self._paho_lock:
             result: int | None = None
             result, mid = await self.hass.async_add_executor_job(

tests/components/mqtt/test_init.py

@@ -1056,6 +1056,38 @@ async def test_not_calling_unsubscribe_with_active_subscribers(
     assert not mqtt_client_mock.unsubscribe.called
 
 
+async def test_unsubscribe_race(hass, mqtt_client_mock, mqtt_mock):
+    """Test not calling unsubscribe() when other subscribers are active."""
+    # Fake that the client is connected
+    mqtt_mock().connected = True
+
+    calls_a = MagicMock()
+    calls_b = MagicMock()
+
+    mqtt_client_mock.reset_mock()
+    unsub = await mqtt.async_subscribe(hass, "test/state", calls_a)
+    unsub()
+    await mqtt.async_subscribe(hass, "test/state", calls_b)
+    await hass.async_block_till_done()
+
+    async_fire_mqtt_message(hass, "test/state", "online")
+    await hass.async_block_till_done()
+    assert not calls_a.called
+    assert calls_b.called
+
+    # We allow either calls [subscribe, unsubscribe, subscribe] or [subscribe, subscribe]
+    expected_calls_1 = [
+        call.subscribe("test/state", 0),
+        call.unsubscribe("test/state"),
+        call.subscribe("test/state", 0),
+    ]
+    expected_calls_2 = [
+        call.subscribe("test/state", 0),
+        call.subscribe("test/state", 0),
+    ]
+    assert mqtt_client_mock.mock_calls in (expected_calls_1, expected_calls_2)
+
+
 @pytest.mark.parametrize(
     "mqtt_config",
     [{mqtt.CONF_BROKER: "mock-broker", mqtt.CONF_DISCOVERY: False}],