Raise error if sensor has translated and hardcoded unit (#131657)

homeassistant/components/sensor/__init__.py

@@ -547,6 +547,12 @@ class SensorEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
             unit_of_measurement
             := self.platform.default_language_platform_translations.get(translation_key)
         ):
+            if native_unit_of_measurement is not None:
+                raise ValueError(
+                    f"Sensor {type(self)} from integration '{self.platform.platform_name}' "
+                    f"has a translation key for unit_of_measurement '{unit_of_measurement}', "
+                    f"but also has a native_unit_of_measurement '{native_unit_of_measurement}'"
+                )
             return unit_of_measurement
 
         # Lowest priority: Native unit

tests/components/sensor/test_init.py

@@ -504,7 +504,6 @@ async def test_translated_unit(
         entity0.entity_description = SensorEntityDescription(
             "test",
             translation_key="test_translation_key",
-            native_unit_of_measurement="ignored_unit",
         )
         setup_test_component_platform(hass, sensor.DOMAIN, [entity0])
 
@@ -518,6 +517,37 @@ async def test_translated_unit(
         assert state.attributes[ATTR_UNIT_OF_MEASUREMENT] == "Tests"
 
 
+async def test_translated_unit_with_native_unit_raises(
+    hass: HomeAssistant,
+) -> None:
+    """Test that translated unit."""
+
+    with patch(
+        "homeassistant.helpers.service.translation.async_get_translations",
+        return_value={
+            "component.test.entity.sensor.test_translation_key.unit_of_measurement": "Tests"
+        },
+    ):
+        entity0 = MockSensor(
+            name="Test",
+            native_value="123",
+            unique_id="very_unique",
+        )
+        entity0.entity_description = SensorEntityDescription(
+            "test",
+            translation_key="test_translation_key",
+            native_unit_of_measurement="bad_unit",
+        )
+        setup_test_component_platform(hass, sensor.DOMAIN, [entity0])
+
+        assert await async_setup_component(
+            hass, "sensor", {"sensor": {"platform": "test"}}
+        )
+        await hass.async_block_till_done()
+        # Setup fails so entity_id is None
+        assert entity0.entity_id is None
+
+
 @pytest.mark.parametrize(
     (
         "device_class",