From 68f8b2cab5ee68156072ebb831b4dd6300107b67 Mon Sep 17 00:00:00 2001
From: Jan Bouwhuis <jbouwh@users.noreply.github.com>
Date: Sun, 19 Nov 2023 19:50:25 +0100
Subject: [PATCH] Fix mqtt json light allows to set brightness value >255
 (#104220)

---
 .../components/mqtt/light/schema_json.py       | 11 +++++++----
 tests/components/mqtt/test_light_json.py       | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/homeassistant/components/mqtt/light/schema_json.py b/homeassistant/components/mqtt/light/schema_json.py
index 6f70ff34051..2a2a262be36 100644
--- a/homeassistant/components/mqtt/light/schema_json.py
+++ b/homeassistant/components/mqtt/light/schema_json.py
@@ -367,10 +367,13 @@ class MqttLightJson(MqttEntity, LightEntity, RestoreEntity):
             if brightness_supported(self.supported_color_modes):
                 try:
                     if brightness := values["brightness"]:
-                        self._attr_brightness = int(
-                            brightness  # type: ignore[operator]
-                            / float(self._config[CONF_BRIGHTNESS_SCALE])
-                            * 255
+                        self._attr_brightness = min(
+                            int(
+                                brightness  # type: ignore[operator]
+                                / float(self._config[CONF_BRIGHTNESS_SCALE])
+                                * 255
+                            ),
+                            255,
                         )
                     else:
                         _LOGGER.debug(
diff --git a/tests/components/mqtt/test_light_json.py b/tests/components/mqtt/test_light_json.py
index e7471829856..b3dd3a9a4e3 100644
--- a/tests/components/mqtt/test_light_json.py
+++ b/tests/components/mqtt/test_light_json.py
@@ -1785,6 +1785,24 @@ async def test_brightness_scale(
     assert state.state == STATE_ON
     assert state.attributes.get("brightness") == 255
 
+    # Turn on the light with half brightness
+    async_fire_mqtt_message(
+        hass, "test_light_bright_scale", '{"state":"ON", "brightness": 50}'
+    )
+
+    state = hass.states.get("light.test")
+    assert state.state == STATE_ON
+    assert state.attributes.get("brightness") == 128
+
+    # Test limmiting max brightness
+    async_fire_mqtt_message(
+        hass, "test_light_bright_scale", '{"state":"ON", "brightness": 103}'
+    )
+
+    state = hass.states.get("light.test")
+    assert state.state == STATE_ON
+    assert state.attributes.get("brightness") == 255
+
 
 @pytest.mark.parametrize(
     "hass_config",