Fix Google Assistant temperature control for entity without mo… (#33107)

homeassistant/components/google_assistant/trait.py

@@ -647,6 +647,14 @@ class TemperatureSettingTrait(_Trait):
 
         elif domain == climate.DOMAIN:
             modes = self.climate_google_modes
+
+            # Some integrations don't support modes (e.g. opentherm), but Google doesn't
+            # support changing the temperature if we don't have any modes. If there's
+            # only one Google doesn't support changing it, so the default mode here is
+            # only cosmetic.
+            if len(modes) == 0:
+                modes.append("heat")
+
             if "off" in modes and any(
                 mode in modes for mode in ("heatcool", "heat", "cool")
             ):

tests/components/google_assistant/test_trait.py

@@ -557,6 +557,32 @@ async def test_temperature_setting_climate_onoff(hass):
     assert len(calls) == 1
 
 
+async def test_temperature_setting_climate_no_modes(hass):
+    """Test TemperatureSetting trait support for climate domain not supporting any modes."""
+    assert helpers.get_google_type(climate.DOMAIN, None) is not None
+    assert trait.TemperatureSettingTrait.supported(climate.DOMAIN, 0, None)
+
+    hass.config.units.temperature_unit = TEMP_CELSIUS
+
+    trt = trait.TemperatureSettingTrait(
+        hass,
+        State(
+            "climate.bla",
+            climate.HVAC_MODE_AUTO,
+            {
+                climate.ATTR_HVAC_MODES: [],
+                climate.ATTR_MIN_TEMP: None,
+                climate.ATTR_MAX_TEMP: None,
+            },
+        ),
+        BASIC_CONFIG,
+    )
+    assert trt.sync_attributes() == {
+        "availableThermostatModes": "heat",
+        "thermostatTemperatureUnit": "C",
+    }
+
+
 async def test_temperature_setting_climate_range(hass):
     """Test TemperatureSetting trait support for climate domain - range."""
     assert helpers.get_google_type(climate.DOMAIN, None) is not None