Cleanup code for parsing yaml MQTT config (#86944)

* Cleanup code for parsing yaml configs

* Add abstractmethod decorator to async_update

* Replace get() with default-list ensured by schema

homeassistant/components/mqtt/mixins.py

@@ -290,24 +290,6 @@ class SetupEntity(Protocol):
         """Define setup_entities type."""
 
 
-async def async_get_platform_config_from_yaml(
-    hass: HomeAssistant,
-    platform_domain: str,
-    config_yaml: ConfigType | None = None,
-) -> list[ConfigType]:
-    """Return a list of validated configurations for the domain."""
-    platform_configs: Any | None
-    mqtt_data = get_mqtt_data(hass)
-    if config_yaml is None:
-        config_yaml = mqtt_data.config
-    if not config_yaml:
-        return []
-    if not (platform_configs := config_yaml.get(platform_domain)):
-        return []
-    assert isinstance(platform_configs, list)
-    return platform_configs
-
-
 async def async_setup_entry_helper(
     hass: HomeAssistant,
     domain: str,
@@ -359,14 +341,7 @@ async def async_setup_entry_helper(
             return
         if domain not in config_yaml:
             return
-        await asyncio.gather(
-            *[
-                async_setup(config)
-                for config in await async_get_platform_config_from_yaml(
-                    hass, domain, config_yaml
-                )
-            ]
-        )
+        await asyncio.gather(*[async_setup(config) for config in config_yaml[domain]])
 
     # discover manual configured MQTT items
     mqtt_data.reload_handlers[domain] = _async_setup_entities
@@ -800,6 +775,7 @@ class MqttDiscoveryDeviceUpdate(ABC):
                 self.hass, self._device_id, self._config_entry_id
             )
 
+    @abstractmethod
     async def async_update(self, discovery_data: MQTTDiscoveryPayload) -> None:
         """Handle the update of platform specific parts, extend to the platform."""
 

tests/components/mqtt/test_init.py

@@ -3062,3 +3062,16 @@ async def test_link_config_entry(hass, tmp_path, caplog):
     # reload manual configured items and assert again
     await help_test_reload_with_config(hass, caplog, tmp_path, config_manual)
     assert _check_entities() == 2
+
+
+@patch("homeassistant.components.mqtt.PLATFORMS", [Platform.SENSOR])
+@pytest.mark.parametrize(
+    "config_manual",
+    [
+        {"mqtt": {"sensor": []}},
+        {"mqtt": {"broker": "test"}},
+    ],
+)
+async def test_setup_manual_entity_from_yaml(hass: HomeAssistant, config_manual):
+    """Test setup with empty platform keys."""
+    await help_test_setup_manual_entity_from_yaml(hass, config_manual)