Add hot reload for derivative (#156898)

Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

homeassistant/components/derivative/icons.json

@@ -5,5 +5,10 @@
         "default": "mdi:chart-line"
       }
     }
+  },
+  "services": {
+    "reload": {
+      "service": "mdi:reload"
+    }
   }
 }

homeassistant/components/derivative/sensor.py

@@ -23,6 +23,7 @@ from homeassistant.const import (
     CONF_UNIQUE_ID,
     STATE_UNAVAILABLE,
     STATE_UNKNOWN,
+    Platform,
     UnitOfTime,
 )
 from homeassistant.core import (
@@ -45,6 +46,7 @@ from homeassistant.helpers.event import (
     async_track_state_change_event,
     async_track_state_report_event,
 )
+from homeassistant.helpers.reload import async_setup_reload_service
 from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType
 
 from .const import (
@@ -54,6 +56,7 @@ from .const import (
     CONF_UNIT,
     CONF_UNIT_PREFIX,
     CONF_UNIT_TIME,
+    DOMAIN,
 )
 
 _LOGGER = logging.getLogger(__name__)
@@ -147,6 +150,8 @@ async def async_setup_platform(
     discovery_info: DiscoveryInfoType | None = None,
 ) -> None:
     """Set up the derivative sensor."""
+    await async_setup_reload_service(hass, DOMAIN, [Platform.SENSOR])
+
     derivative = DerivativeSensor(
         hass,
         name=config.get(CONF_NAME),
@@ -288,14 +293,14 @@ class DerivativeSensor(RestoreSensor, SensorEntity):
         )
         self.async_write_ha_state()
 
-    async def async_added_to_hass(self) -> None:
-        """Handle entity which will be added."""
-        await super().async_added_to_hass()
+    async def _handle_restore(self) -> None:
         restored_data = await self.async_get_last_sensor_data()
         if restored_data:
-            self._attr_native_unit_of_measurement = (
-                restored_data.native_unit_of_measurement
-            )
+            if self._attr_native_unit_of_measurement is None:
+                # Only restore the unit if it's not assigned from YAML
+                self._attr_native_unit_of_measurement = (
+                    restored_data.native_unit_of_measurement
+                )
             try:
                 self._attr_native_value = round(
                     Decimal(restored_data.native_value),  # type: ignore[arg-type]
@@ -304,6 +309,11 @@ class DerivativeSensor(RestoreSensor, SensorEntity):
             except (InvalidOperation, TypeError):
                 self._attr_native_value = None
 
+    async def async_added_to_hass(self) -> None:
+        """Handle entity which will be added."""
+        await super().async_added_to_hass()
+        await self._handle_restore()
+
         source_state = self.hass.states.get(self._sensor_source_id)
         self._derive_and_set_attributes_from_state(source_state)
 

homeassistant/components/derivative/services.yaml

@@ -0,0 +1 @@
+reload:

homeassistant/components/derivative/strings.json

@@ -58,5 +58,11 @@
       }
     }
   },
+  "services": {
+    "reload": {
+      "description": "Reloads derivative sensors from the YAML-configuration.",
+      "name": "[%key:common::action::reload%]"
+    }
+  },
   "title": "Derivative sensor"
 }

tests/components/derivative/fixtures/configuration.yaml

@@ -0,0 +1,9 @@
+sensor:
+  - platform: derivative
+    name: derivative
+    source: "sensor.energy"
+    unit: "W"
+  - platform: derivative
+    name: derivative_new
+    source: "sensor.energy"
+    unit: "W"

tests/components/derivative/test_sensor.py

@@ -4,13 +4,16 @@ from datetime import timedelta
 from math import sin
 import random
 from typing import Any
+from unittest.mock import patch
 
 from freezegun import freeze_time
 import pytest
 
+from homeassistant import config as hass_config, core as ha
 from homeassistant.components.derivative.const import DOMAIN
 from homeassistant.components.sensor import ATTR_STATE_CLASS, SensorStateClass
 from homeassistant.const import (
+    SERVICE_RELOAD,
     STATE_UNAVAILABLE,
     STATE_UNKNOWN,
     UnitOfPower,
@@ -31,6 +34,7 @@ from homeassistant.util import dt as dt_util
 from tests.common import (
     MockConfigEntry,
     async_fire_time_changed,
+    get_fixture_path,
     mock_restore_cache_with_extra_data,
 )
 
@@ -1000,6 +1004,64 @@ async def test_source_unit_change(
         assert state.attributes.get("unit_of_measurement") == "dogs/s"
 
 
+async def test_reload(hass: HomeAssistant) -> None:
+    """Test hot-reloading derivative YAML sensors."""
+    hass.state = ha.CoreState.not_running
+    hass.states.async_set("sensor.energy", "0.0")
+
+    config = {
+        "sensor": [
+            {
+                "platform": "derivative",
+                "name": "derivative",
+                "source": "sensor.energy",
+                "unit": "kW",
+            },
+            {
+                "platform": "derivative",
+                "name": "derivative_remove",
+                "source": "sensor.energy",
+                "unit": "kW",
+            },
+        ]
+    }
+
+    assert await async_setup_component(hass, "sensor", config)
+
+    await hass.async_block_till_done()
+    await hass.async_start()
+    await hass.async_block_till_done()
+
+    assert len(hass.states.async_all()) == 3
+    state = hass.states.get("sensor.derivative")
+    assert state is not None
+    assert state.attributes.get("unit_of_measurement") == "kW"
+    assert hass.states.get("sensor.derivative_remove")
+
+    yaml_path = get_fixture_path("configuration.yaml", "derivative")
+    with patch.object(hass_config, "YAML_CONFIG_FILE", yaml_path):
+        await hass.services.async_call(
+            DOMAIN,
+            SERVICE_RELOAD,
+            {},
+            blocking=True,
+        )
+        await hass.async_block_till_done()
+
+    assert len(hass.states.async_all()) == 3
+
+    # Check that we can change the unit of an existing sensor
+    state = hass.states.get("sensor.derivative")
+    assert state is not None
+    assert state.attributes.get("unit_of_measurement") == "W"
+
+    # Check that we can remove a derivative sensor
+    assert hass.states.get("sensor.derivative_remove") is None
+
+    # Check that we can add a new derivative sensor
+    assert hass.states.get("sensor.derivative_new")
+
+
 async def test_unique_id(
     hass: HomeAssistant,
     entity_registry: er.EntityRegistry,