Fix race when handling rapid succession of MQTT discovery messages

homeassistant/components/mqtt/mixins.py

@@ -572,9 +572,7 @@ async def discovery_callback(payload):
                 else:
                     # Non-empty, unchanged payload: Ignore to avoid changing states
                     _LOGGER.info("Ignoring unchanged update for: %s", self.entity_id)
-            async_dispatcher_send(
-                self.hass, MQTT_DISCOVERY_DONE.format(discovery_hash), None
-            )
+            self.async_send_discovery_done()
 
         if discovery_hash:
             debug_info.add_entity_discovery_data(
@@ -587,9 +585,18 @@ async def discovery_callback(payload):
                 MQTT_DISCOVERY_UPDATED.format(discovery_hash),
                 discovery_callback,
             )
-            async_dispatcher_send(
-                self.hass, MQTT_DISCOVERY_DONE.format(discovery_hash), None
-            )
+
+    @callback
+    def async_send_discovery_done(self) -> None:
+        """Acknowledge a discovery message has been handled."""
+        discovery_hash = (
+            self._discovery_data[ATTR_DISCOVERY_HASH] if self._discovery_data else None
+        )
+        if not discovery_hash:
+            return
+        async_dispatcher_send(
+            self.hass, MQTT_DISCOVERY_DONE.format(discovery_hash), None
+        )
 
     async def async_removed_from_registry(self) -> None:
         """Clear retained discovery topic in broker."""
@@ -728,6 +735,7 @@ async def async_added_to_hass(self):
         await super().async_added_to_hass()
         self._prepare_subscribe_topics()
         await self._subscribe_topics()
+        self.async_send_discovery_done()
 
     async def discovery_update(self, discovery_payload):
         """Handle updated discovery message."""

tests/components/mqtt/test_discovery.py

@@ -550,6 +550,58 @@ def callback(event):
     assert events[3].data["old_state"] is None
 
 
+async def test_rapid_reconfigure(hass, mqtt_mock, caplog):
+    """Test immediate reconfigure of added component."""
+
+    events = []
+
+    @ha.callback
+    def callback(event):
+        """Verify event got called."""
+        events.append(event)
+
+    hass.bus.async_listen(EVENT_STATE_CHANGED, callback)
+
+    # Discovery immediately followed by reconfig
+    async_fire_mqtt_message(hass, "homeassistant/binary_sensor/bla/config", "")
+    async_fire_mqtt_message(
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Beer", "state_topic": "test-topic1" }',
+    )
+    async_fire_mqtt_message(
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Milk", "state_topic": "test-topic2" }',
+    )
+    async_fire_mqtt_message(
+        hass,
+        "homeassistant/binary_sensor/bla/config",
+        '{ "name": "Wine", "state_topic": "test-topic3" }',
+    )
+    await hass.async_block_till_done()
+
+    assert len(hass.states.async_entity_ids("binary_sensor")) == 1
+    state = hass.states.get("binary_sensor.beer")
+    assert state is not None
+
+    assert len(events) == 3
+    # Add the entity
+    assert events[0].data["entity_id"] == "binary_sensor.beer"
+    assert events[0].data["old_state"] is None
+    assert events[0].data["new_state"].attributes["friendly_name"] == "Beer"
+    # Update the entity
+    assert events[1].data["entity_id"] == "binary_sensor.beer"
+    assert events[1].data["new_state"] is not None
+    assert events[1].data["old_state"] is not None
+    assert events[1].data["new_state"].attributes["friendly_name"] == "Milk"
+    # Update the entity
+    assert events[2].data["entity_id"] == "binary_sensor.beer"
+    assert events[2].data["new_state"] is not None
+    assert events[2].data["old_state"] is not None
+    assert events[2].data["new_state"].attributes["friendly_name"] == "Wine"
+
+
 async def test_duplicate_removal(hass, mqtt_mock, caplog):
     """Test for a non duplicate component."""
     async_fire_mqtt_message(

tests/conftest.py

@@ -618,6 +618,8 @@ async def mqtt_mock(hass, mqtt_client_mock, mqtt_config):
     )
     mqtt_component_mock.conf = hass.data["mqtt"].conf  # For diagnostics
     mqtt_component_mock._mqttc = mqtt_client_mock
+    # connected set to True to get a more realistics behavior when subscribing
+    hass.data["mqtt"].connected = True
 
     hass.data["mqtt"] = mqtt_component_mock
     component = hass.data["mqtt"]