Fix Matter fan and light dividing by zero on out-of-spec device ranges (#182645)

homeassistant/components/matter/fan.py

@@ -270,9 +270,13 @@ class MatterFan(MatterEntity, FanEntity):
         # does not leave a stale speed_count / percentage_step.
         self._attr_speed_count = 100
         if feature_map & FanControlFeature.kMultiSpeed:
-            self._attr_speed_count = int(
+            speed_max = int(
                 self.get_matter_attribute_value(clusters.FanControl.Attributes.SpeedMax)
             )
+            # the step size divides by the speed count, so a device reporting
+            # no speeds keeps the default
+            if speed_max > 0:
+                self._attr_speed_count = speed_max
         if feature_map & FanControlFeature.kRocking:
             # NOTE: the Matter model allows that a device can have multiple/different
             # rock directions while HA doesn't allow this in the entity model.

homeassistant/components/matter/light.py

@@ -84,6 +84,19 @@ TRANSITION_BLOCKLIST = (
 )
 
 
+def _level_range(level_control: clusters.LevelControl) -> tuple[int, int]:
+    """Return the level range of the device.
+
+    Brightness scaling divides by the width of the range, so a device that
+    reports a range without width gets the default range instead.
+    """
+    min_level = level_control.minLevel or 1
+    max_level = level_control.maxLevel or 254
+    if max_level <= min_level:
+        return (1, 254)
+    return (min_level, max_level)
+
+
 async def async_setup_entry(
     hass: HomeAssistant,
     config_entry: MatterConfigEntry,
@@ -177,13 +190,7 @@ class MatterLight(MatterEntity, LightEntity):
 
         assert level_control is not None
 
-        level = round(
-            renormalize(
-                brightness,
-                (0, 255),
-                (level_control.minLevel or 1, level_control.maxLevel or 254),
-            )
-        )
+        level = round(renormalize(brightness, (0, 255), _level_range(level_control)))
 
         await self.send_device_command(
             clusters.LevelControl.Commands.MoveToLevelWithOnOff(
@@ -280,9 +287,7 @@ class MatterLight(MatterEntity, LightEntity):
 
         return round(
             renormalize(
-                level_control.currentLevel,
-                (level_control.minLevel or 1, level_control.maxLevel or 254),
-                (0, 255),
+                level_control.currentLevel, _level_range(level_control), (0, 255)
             )
         )
 

tests/components/matter/test_fan.py

@@ -504,3 +504,24 @@ async def test_fan_set_percentage_without_multispeed(
         attribute_path="1/514/2",
         value=75,
     )
+
+
+@pytest.mark.parametrize("node_fixture", ["mock_air_purifier"])
+@pytest.mark.parametrize("attributes", [{"1/514/4": 0}])
+async def test_fan_without_speed_steps(
+    hass: HomeAssistant,
+    matter_client: MagicMock,
+    matter_node: MatterNode,
+) -> None:
+    """Test a fan reporting no speed steps keeps the default step size."""
+    entity_id = "fan.mock_air_purifier"
+    state = hass.states.get(entity_id)
+    assert state
+    assert state.attributes["percentage_step"] == 1
+
+    # a proper speed count is picked up when the features are recalculated
+    set_node_attribute(matter_node, 1, 514, 4, 5)
+    set_node_attribute(matter_node, 1, 514, 65532, 47)
+    await trigger_subscription_callback(hass, matter_client)
+    state = hass.states.get(entity_id)
+    assert state.attributes["percentage_step"] == 20

tests/components/matter/test_light.py

@@ -565,3 +565,36 @@ async def test_light_unexpected_color_mode(
             transitionTime=0,
         ),
     )
+
+
+@pytest.mark.parametrize("node_fixture", ["mock_dimmable_light"])
+async def test_dimmable_light_without_level_range(
+    hass: HomeAssistant,
+    matter_client: MagicMock,
+    matter_node: MatterNode,
+) -> None:
+    """Test a light reporting a level range without width uses the default range."""
+    entity_id = "light.mock_dimmable_light"
+    set_node_attribute(matter_node, 1, 8, 2, 5)
+    set_node_attribute(matter_node, 1, 8, 3, 5)
+    set_node_attribute(matter_node, 1, 8, 0, 5)
+    await trigger_subscription_callback(hass, matter_client)
+
+    state = hass.states.get(entity_id)
+    assert state
+    assert state.attributes["brightness"] == 4
+
+    await hass.services.async_call(
+        "light",
+        "turn_on",
+        {"entity_id": entity_id, "brightness": 128},
+        blocking=True,
+    )
+    assert matter_client.send_device_command.call_args == call(
+        node_id=matter_node.node_id,
+        endpoint_id=1,
+        command=clusters.LevelControl.Commands.MoveToLevelWithOnOff(
+            level=128,
+            transitionTime=0,
+        ),
+    )