Set mqtt entity name to `null` when it is a duplicate of the device name (#97304)

homeassistant/components/mqtt/mixins.py

@@ -1135,7 +1135,16 @@ class MqttEntity(
                     "MQTT device information always needs to include a name, got %s, "
                     "if device information is shared between multiple entities, the device "
                     "name must be included in each entity's device configuration",
+                    config,
                 )
+            elif config[CONF_DEVICE][CONF_NAME] == entity_name:
+                _LOGGER.warning(
+                    "MQTT device name is equal to entity name in your config %s, "
+                    "this is not expected. Please correct your configuration. "
+                    "The entity name will be set to `null`",
+                    config,
+                )
+                self._attr_name = None
 
     def _setup_common_attributes_from_config(self, config: ConfigType) -> None:
         """(Re)Setup the common attributes for the entity."""

tests/components/mqtt/test_mixins.py

@@ -212,6 +212,26 @@ async def test_availability_with_shared_state_topic(
             None,
             True,
         ),
+        (  # entity_name_and_device_name_the_sane
+            {
+                mqtt.DOMAIN: {
+                    sensor.DOMAIN: {
+                        "name": "Hello world",
+                        "state_topic": "test-topic",
+                        "unique_id": "veryunique",
+                        "device_class": "humidity",
+                        "device": {
+                            "identifiers": ["helloworld"],
+                            "name": "Hello world",
+                        },
+                    }
+                }
+            },
+            "sensor.hello_world",
+            "Hello world",
+            "Hello world",
+            False,
+        ),
     ],
     ids=[
         "default_entity_name_without_device_name",
@@ -222,6 +242,7 @@ async def test_availability_with_shared_state_topic(
         "name_set_no_device_name_set",
         "none_entity_name_with_device_name",
         "none_entity_name_without_device_name",
+        "entity_name_and_device_name_the_sane",
     ],
 )
 @patch("homeassistant.components.mqtt.PLATFORMS", [Platform.SENSOR])