Improve MQTT json light brightness scaling (#104510)

* Improve MQTT json light brightness scaling

* Revert unrelated changes

* Format

homeassistant/components/mqtt/light/schema_json.py

@@ -367,13 +367,10 @@ class MqttLightJson(MqttEntity, LightEntity, RestoreEntity):
             if brightness_supported(self.supported_color_modes):
                 try:
                     if brightness := values["brightness"]:
+                        scale = self._config[CONF_BRIGHTNESS_SCALE]
                         self._attr_brightness = min(
-                            int(
-                                brightness  # type: ignore[operator]
-                                / float(self._config[CONF_BRIGHTNESS_SCALE])
-                                * 255
-                            ),
                             255,
+                            round(brightness * 255 / scale),  # type: ignore[operator]
                         )
                     else:
                         _LOGGER.debug(

tests/components/mqtt/test_light_json.py

@@ -1792,7 +1792,7 @@ async def test_brightness_scale(
 
     state = hass.states.get("light.test")
     assert state.state == STATE_ON
-    assert state.attributes.get("brightness") == 128
+    assert state.attributes.get("brightness") == 129
 
     # Test limmiting max brightness
     async_fire_mqtt_message(
@@ -1862,7 +1862,7 @@ async def test_white_scale(
 
     state = hass.states.get("light.test")
     assert state.state == STATE_ON
-    assert state.attributes.get("brightness") == 128
+    assert state.attributes.get("brightness") == 129
 
 
 @pytest.mark.parametrize(