fix issue where energy group calculation had minor errors because of …

…rounding precision (#2259)

* fix: issue where energy group calculation had minor errors because of rounding precision

* fix: mypy

custom_components/powercalc/sensors/group.py

@@ -516,6 +516,7 @@ def __init__(
         self.entity_id = entity_id
         self.source_device_id = device_id
         self._prev_state_store: PreviousStateStore = PreviousStateStore(hass)
+        self._native_value_exact = Decimal(0)
 
     async def async_added_to_hass(self) -> None:
         """Register state listeners."""
@@ -527,15 +528,9 @@ async def async_added_to_hass(self) -> None:
             last_sensor_state = await self.async_get_last_sensor_data()
             try:
                 if last_sensor_state and last_sensor_state.native_value:
-                    self._attr_native_value = round(
-                        Decimal(last_sensor_state.native_value),  # type: ignore
-                        self._rounding_digits,
-                    )
+                    self._set_native_value(Decimal(last_sensor_state.native_value))  #type: ignore
                 elif last_state:
-                    self._attr_native_value = round(
-                        Decimal(last_state.state),
-                        self._rounding_digits,
-                    )
+                    self._set_native_value(Decimal(last_state.state))
                 _LOGGER.debug(
                     "%s: Restoring state: %s",
                     self.entity_id,
@@ -600,21 +595,21 @@ def on_state_change(self, _: Any) -> None:  # noqa
         if not available_states:
             if self._sensor_config.get(CONF_IGNORE_UNAVAILABLE_STATE):
                 if isinstance(self, GroupedPowerSensor):
-                    self._attr_native_value = 0
+                    self._set_native_value(Decimal(0))
                 self._attr_available = True
             else:
                 self._attr_available = False
             self.async_write_ha_state()
             return
 
         summed = self.calculate_new_state(available_states, states)
-        self._attr_native_value = round(summed, self._rounding_digits)
+        self._set_native_value(summed)
         self._attr_available = True
         self.async_write_ha_state()
 
     def _get_state_value_in_native_unit(self, state: State) -> Decimal:
         """Convert value of member entity state to match the unit of measurement of the group sensor."""
-        value = float(state.state)
+        value = state.state
         unit_of_measurement = state.attributes.get(ATTR_UNIT_OF_MEASUREMENT)
         if (
             unit_of_measurement
@@ -626,12 +621,17 @@ def _get_state_value_in_native_unit(self, state: State) -> Decimal:
                 else PowerConverter
             )
             value = unit_converter.convert(
-                value,
+                float(value),
                 unit_of_measurement,
                 self._attr_native_unit_of_measurement,
             )
         return Decimal(value)
 
+    def _set_native_value(self, value: Decimal) -> None:
+        self._native_value_exact = value
+        self._attr_native_value = round(value, self._rounding_digits)
+        self.async_write_ha_state()
+
     @abstractmethod
     def calculate_new_state(
         self,
@@ -698,7 +698,7 @@ def __init__(
     async def async_reset(self) -> None:
         """Reset the group sensor and underlying member sensor when supported."""
         _LOGGER.debug("%s: Reset grouped energy sensor", self.entity_id)
-        self._attr_native_value = 0
+        self._set_native_value(Decimal(0))
         self.async_write_ha_state()
 
         for entity_id in self._entities:
@@ -718,7 +718,7 @@ async def async_reset(self) -> None:
 
     async def async_calibrate(self, value: str) -> None:
         _LOGGER.debug("%s: Calibrate group energy sensor to: %s", self.entity_id, value)
-        self._attr_native_value = Decimal(value)
+        self._set_native_value(Decimal(value))
         self.async_write_ha_state()
 
     def calculate_new_state(
@@ -729,8 +729,8 @@ def calculate_new_state(
         """Calculate the new group energy sensor state
         For each member sensor we calculate the delta by looking at the previous known state and compare it to the current.
         """
-        group_sum = Decimal(self._attr_native_value) if self._attr_native_value else Decimal(0)  # type: ignore
-        _LOGGER.debug("%s: Recalculate, current value: %d", self.entity_id, group_sum)
+        group_sum = Decimal(self._native_value_exact) if self._native_value_exact else Decimal(0)
+        _LOGGER.debug("%s: Recalculate, current value: %s", self.entity_id, group_sum)
         for entity_state in member_states:
             if entity_state.state in [STATE_UNKNOWN, STATE_UNAVAILABLE]:
                 _LOGGER.debug(

tests/sensors/test_group.py

@@ -306,7 +306,7 @@ async def test_reset_service(hass: HomeAssistant) -> None:
         )
         await hass.async_block_till_done()
 
-    assert hass.states.get("sensor.testgroup_energy").state == "0"
+    assert hass.states.get("sensor.testgroup_energy").state == "0.0000"
     assert hass.states.get("sensor.test1_energy").state == "0"
     assert hass.states.get("sensor.test2_energy").state == "0"
 
@@ -352,7 +352,7 @@ async def test_calibrate_service(hass: HomeAssistant) -> None:
     )
     await hass.async_block_till_done()
 
-    assert hass.states.get("sensor.testgroup_energy").state == "100"
+    assert hass.states.get("sensor.testgroup_energy").state == "100.0000"
 
 
 async def test_restore_state(hass: HomeAssistant) -> None:
@@ -1128,6 +1128,36 @@ async def test_energy_sensor_delta_updates_new_sensor(hass: HomeAssistant) -> No
         assert hass.states.get("sensor.testgroup_energy").state == "5.3000"
 
 
+async def test_delta_calculation_precision(hass: HomeAssistant) -> None:
+    """
+    Make sure delta calculation is done on exact decimal value, not the rounded value.
+    See: https://github.com/bramstroker/homeassistant-powercalc/issues/2254
+    """
+    await _create_energy_group(
+        hass,
+        "TestGroup",
+        ["sensor.a_energy"],
+    )
+
+    test_values = [
+        ("1197.865543", "1197.8655"),
+        ("1197.868021", "1197.8680"),
+        ("1197.868628", "1197.8686"),
+        ("1197.871022", "1197.8710"),
+        ("1197.871629", "1197.8716"),
+        ("1197.873903", "1197.8739"),
+        ("1197.874396", "1197.8744"),
+        ("1197.876372", "1197.8764"),
+        ("1197.876868", "1197.8769"),
+        ("1197.878879", "1197.8789"),
+        ("1197.879332", "1197.8793"),
+    ]
+
+    for energy_state, expected_group_state in test_values:
+        hass.states.async_set("sensor.a_energy", energy_state, {ATTR_UNIT_OF_MEASUREMENT: UnitOfEnergy.KILO_WATT_HOUR})
+        await hass.async_block_till_done()
+        assert hass.states.get("sensor.testgroup_energy").state == expected_group_state
+
 async def test_energy_sensor_delta_updates_existing_sensor(hass: HomeAssistant) -> None:
     await _create_energy_group(
         hass,
@@ -1428,7 +1458,7 @@ async def test_inital_group_sum_calculated(hass: HomeAssistant) -> None:
 
     group_state = hass.states.get("sensor.testgroup_power")
     assert group_state
-    assert group_state.state == "0"
+    assert group_state.state == "0.00"
 
 
 async def test_additional_energy_sensors(hass: HomeAssistant) -> None: