fix: treat STATE_UNKNOWN as absent on the textual read properties

_optional_float() and as_list() already treated STATE_UNKNOWN as
absent; low_voltage_mode, fan_mode and current_state did not. A device
reporting the literal string "unknown" as its mode was classified as
low voltage, and that string would have been echoed straight back into
a write payload by async_set_low_voltage_state(). Route the textual
properties through a new _optional_str() helper that mirrors
_optional_float()'s STATE_UNKNOWN handling; is_low_voltage now derives
from low_voltage_mode instead of duplicating the check.

Author: ColtHub

pyhilo/device/climate.py

@@ -132,20 +132,26 @@ def _optional_float(self, attribute: str) -> float | None:
         except (TypeError, ValueError):
             return None
 
+    def _optional_str(self, attribute: str) -> str | None:
+        """Return a textual reading, or None when absent or unusable."""
+        value = self.get_value(attribute, None)
+        if value is None or value == STATE_UNKNOWN:
+            return None
+        return str(value)
+
     @property
     def is_low_voltage(self) -> bool:
         """Whether this is a low voltage (24 V) thermostat.
 
         Baseboard thermostats report none of the 24 V attributes and therefore
         keep their heat-only behaviour.
         """
-        return self.get_value(LOW_VOLTAGE_MODE, None) is not None
+        return self.low_voltage_mode is not None
 
     @property
     def low_voltage_mode(self) -> str | None:
         """Operating mode reported by a 24 V thermostat, in Hilo's vocabulary."""
-        value = self.get_value(LOW_VOLTAGE_MODE, None)
-        return None if value is None else str(value)
+        return self._optional_str(LOW_VOLTAGE_MODE)
 
     @property
     def allowed_modes(self) -> list[str]:
@@ -155,8 +161,7 @@ def allowed_modes(self) -> list[str]:
     @property
     def fan_mode(self) -> str | None:
         """Current fan mode, when the device reports one."""
-        value = self.get_value("fan_mode", None)
-        return None if value is None else str(value)
+        return self._optional_str("fan_mode")
 
     @property
     def allowed_fan_modes(self) -> list[str]:
@@ -170,8 +175,7 @@ def current_state(self) -> str | None:
         Exposed for consumers, but deliberately not mapped to hvac_action yet:
         its vocabulary has not been observed in enough operating conditions.
         """
-        value = self.get_value("current_state", None)
-        return None if value is None else str(value)
+        return self._optional_str("current_state")
 
     @property
     def cool_setpoint(self) -> float | None:

tests/test_climate.py

@@ -1,6 +1,6 @@
 from unittest.mock import AsyncMock, MagicMock
 
-from pyhilo.const import HILO_READING_TYPES
+from pyhilo.const import HILO_READING_TYPES, STATE_UNKNOWN
 from pyhilo.device import DeviceAttribute, DeviceReading, get_device_attributes
 from pyhilo.device.climate import Climate, as_list
 
@@ -60,6 +60,9 @@ def test_baseboard_is_not_low_voltage(self):
     def test_device_reporting_a_mode_is_low_voltage(self):
         assert _climate(Thermostat24VMode="COOL").is_low_voltage is True
 
+    def test_device_reporting_unknown_mode_is_not_low_voltage(self):
+        assert _climate(Thermostat24VMode=STATE_UNKNOWN).is_low_voltage is False
+
 
 class TestLowVoltageProperties:
     def test_reads_mode_and_vocabularies(self):
@@ -99,6 +102,15 @@ def test_humidity_rounds_rather_than_truncates(self):
         device = _climate(Thermostat24VMode="COOL", Humidity=57.8)
         assert device.current_humidity == 58
 
+    def test_unknown_state_is_treated_as_absent(self):
+        device = _climate(
+            Thermostat24VMode="COOL",
+            FanMode=STATE_UNKNOWN,
+            CurrentState=STATE_UNKNOWN,
+        )
+        assert device.fan_mode is None
+        assert device.current_state is None
+
 
 class TestSetTemperature:
     async def test_low_voltage_device_delegates_to_low_voltage_state(self):