Do not allow mqtt lights to set brightness to zero (#91296)

* Do not allow mqtt lights to set brightness to zero

* Loglevel to debug

* Typo

homeassistant/components/mqtt/light/schema_basic.py

@@ -468,6 +468,10 @@ class MqttLight(MqttEntity, LightEntity, RestoreEntity):
                 return
 
             device_value = float(payload)
+            if device_value == 0:
+                _LOGGER.debug("Ignoring zero brightness from '%s'", msg.topic)
+                return
+
             percent_bright = device_value / self._config[CONF_BRIGHTNESS_SCALE]
             self._attr_brightness = min(round(percent_bright * 255), 255)
 

homeassistant/components/mqtt/light/schema_json.py

@@ -378,11 +378,18 @@ class MqttLightJson(MqttEntity, LightEntity, RestoreEntity):
 
             if brightness_supported(self.supported_color_modes):
                 try:
-                    self._attr_brightness = int(
+                    if brightness := values["brightness"]:
-                        values["brightness"]  # type: ignore[operator]
+                        self._attr_brightness = int(
-                        / float(self._config[CONF_BRIGHTNESS_SCALE])
+                            brightness  # type: ignore[operator]
-                        * 255
+                            / float(self._config[CONF_BRIGHTNESS_SCALE])
-                    )
+                            * 255
+                        )
+                    else:
+                        _LOGGER.debug(
+                            "Ignoring zero brightness value for entity %s",
+                            self.entity_id,
+                        )
+
                 except KeyError:
                     pass
                 except (TypeError, ValueError):

homeassistant/components/mqtt/light/schema_template.py

@@ -236,11 +236,20 @@ class MqttLightTemplate(MqttEntity, LightEntity, RestoreEntity):
 
             if CONF_BRIGHTNESS_TEMPLATE in self._config:
                 try:
-                    self._attr_brightness = int(
+                    if brightness := int(
                         self._value_templates[CONF_BRIGHTNESS_TEMPLATE](msg.payload)
-                    )
+                    ):
+                        self._attr_brightness = brightness
+                    else:
+                        _LOGGER.debug(
+                            "Ignoring zero brightness value for entity %s",
+                            self.entity_id,
+                        )
+
                 except ValueError:
-                    _LOGGER.warning("Invalid brightness value received")
+                    _LOGGER.warning(
+                        "Invalid brightness value received from %s", msg.topic
+                    )
 
             if CONF_COLOR_TEMP_TEMPLATE in self._config:
                 try:

tests/components/mqtt/test_light.py

@@ -794,6 +794,19 @@ async def test_controlling_state_via_topic_with_templates(
     assert state.attributes.get(light.ATTR_COLOR_MODE) == "xy"
     assert state.attributes.get(light.ATTR_SUPPORTED_COLOR_MODES) == color_modes
 
+    async_fire_mqtt_message(hass, "test_light_rgb/brightness/status", '{"hello": 100}')
+    state = hass.states.get("light.test")
+    assert state.attributes.get("brightness") == 100
+
+    async_fire_mqtt_message(hass, "test_light_rgb/brightness/status", '{"hello": 50}')
+    state = hass.states.get("light.test")
+    assert state.attributes.get("brightness") == 50
+
+    # test zero brightness received is ignored
+    async_fire_mqtt_message(hass, "test_light_rgb/brightness/status", '{"hello": 0}')
+    state = hass.states.get("light.test")
+    assert state.attributes.get("brightness") == 50
+
 
 @pytest.mark.parametrize(
     "hass_config",

tests/components/mqtt/test_light_json.py

@@ -493,6 +493,37 @@ async def test_controlling_state_via_topic(
     light_state = hass.states.get("light.test")
     assert light_state.attributes.get("effect") == "colorloop"
 
+    async_fire_mqtt_message(
+        hass,
+        "test_light_rgb",
+        '{"state":"ON",'
+        '"color":{"r":255,"g":255,"b":255},'
+        '"brightness":128,'
+        '"color_temp":155,'
+        '"effect":"colorloop"}',
+    )
+    light_state = hass.states.get("light.test")
+    assert light_state.state == STATE_ON
+    assert light_state.attributes.get("brightness") == 128
+
+    async_fire_mqtt_message(
+        hass,
+        "test_light_rgb",
+        '{"state":"OFF","brightness":0}',
+    )
+    light_state = hass.states.get("light.test")
+    assert light_state.state == STATE_OFF
+    assert light_state.attributes.get("brightness") is None
+
+    # test previous zero brightness received was ignored and brightness is restored
+    async_fire_mqtt_message(hass, "test_light_rgb", '{"state":"ON"}')
+    light_state = hass.states.get("light.test")
+    assert light_state.attributes.get("brightness") == 128
+
+    async_fire_mqtt_message(hass, "test_light_rgb", '{"state":"ON","brightness":0}')
+    light_state = hass.states.get("light.test")
+    assert light_state.attributes.get("brightness") == 128
+
 
 @pytest.mark.parametrize(
     "hass_config",

tests/components/mqtt/test_light_template.py

@@ -330,6 +330,12 @@ async def test_state_brightness_color_effect_temp_change_via_topic(
     light_state = hass.states.get("light.test")
     assert light_state.attributes["brightness"] == 100
 
+    # ignore a zero brightness
+    async_fire_mqtt_message(hass, "test_light_rgb", "on,0")
+
+    light_state = hass.states.get("light.test")
+    assert light_state.attributes["brightness"] == 100
+
     # change the color temp
     async_fire_mqtt_message(hass, "test_light_rgb", "on,,195")