Make unit converter use a factory to avoid looking up the ratios each conversion

homeassistant/components/recorder/statistics.py

@@ -219,50 +219,34 @@ def _get_statistic_to_display_unit_converter(
     if display_unit == statistic_unit:
         return None
 
-    convert = converter.convert
-
-    def _from_normalized_unit(val: float | None) -> float | None:
-        """Return val."""
-        if val is None:
-            return val
-        return convert(val, statistic_unit, display_unit)
-
-    return _from_normalized_unit
+    return converter.converter_factory_allow_none(
+        from_unit=statistic_unit, to_unit=display_unit
+    )
 
 
 def _get_display_to_statistic_unit_converter(
     display_unit: str | None,
     statistic_unit: str | None,
-) -> Callable[[float], float]:
+) -> Callable[[float], float] | None:
     """Prepare a converter from the display unit to the statistics unit."""
-
-    def no_conversion(val: float) -> float:
-        """Return val."""
-        return val
-
-    if (converter := STATISTIC_UNIT_TO_UNIT_CONVERTER.get(statistic_unit)) is None:
-        return no_conversion
-
-    return partial(converter.convert, from_unit=display_unit, to_unit=statistic_unit)
+    if (
+        display_unit == statistic_unit
+        or (converter := STATISTIC_UNIT_TO_UNIT_CONVERTER.get(statistic_unit)) is None
+    ):
+        return None
+    return converter.converter_factory(from_unit=display_unit, to_unit=statistic_unit)
 
 
 def _get_unit_converter(
     from_unit: str, to_unit: str
-) -> Callable[[float | None], float | None]:
+) -> Callable[[float | None], float | None] | None:
     """Prepare a converter from a unit to another unit."""
-
-    def convert_units(
-        val: float | None, conv: type[BaseUnitConverter], from_unit: str, to_unit: str
-    ) -> float | None:
-        """Return converted val."""
-        if val is None:
-            return val
-        return conv.convert(val, from_unit=from_unit, to_unit=to_unit)
-
     for conv in STATISTIC_UNIT_TO_UNIT_CONVERTER.values():
         if from_unit in conv.VALID_UNITS and to_unit in conv.VALID_UNITS:
-            return partial(
-                convert_units, conv=conv, from_unit=from_unit, to_unit=to_unit
+            if from_unit == to_unit:
+                return None
+            return conv.converter_factory_allow_none(
+                from_unit=from_unit, to_unit=to_unit
             )
     raise HomeAssistantError
 
@@ -2290,10 +2274,10 @@ def adjust_statistics(
             return True
 
         statistic_unit = metadata[statistic_id][1]["unit_of_measurement"]
-        convert = _get_display_to_statistic_unit_converter(
+        if convert := _get_display_to_statistic_unit_converter(
             adjustment_unit, statistic_unit
-        )
-        sum_adjustment = convert(sum_adjustment)
+        ):
+            sum_adjustment = convert(sum_adjustment)
 
         _adjust_sum_statistics(
             session,
@@ -2360,7 +2344,14 @@ def change_statistics_unit(
 
         metadata_id = metadata[0]
 
-        convert = _get_unit_converter(old_unit, new_unit)
+        if not (convert := _get_unit_converter(old_unit, new_unit)):
+            _LOGGER.warning(
+                "Statistics unit of measurement for %s is already %s",
+                statistic_id,
+                new_unit,
+            )
+            return
+
         tables: tuple[type[StatisticsBase], ...] = (
             Statistics,
             StatisticsShortTerm,

homeassistant/util/unit_conversion.py

@@ -1,6 +1,9 @@
 """Typing Helpers for Home Assistant."""
 from __future__ import annotations
 
+from collections.abc import Callable
+from functools import lru_cache
+
 from homeassistant.const import (
     CONCENTRATION_PARTS_PER_BILLION,
     CONCENTRATION_PARTS_PER_MILLION,
@@ -67,8 +70,41 @@ class BaseUnitConverter:
     @classmethod
     def convert(cls, value: float, from_unit: str | None, to_unit: str | None) -> float:
         """Convert one unit of measurement to another."""
+        return cls.converter_factory(from_unit, to_unit)(value)
+
+    @classmethod
+    @lru_cache(maxsize=128)
+    def converter_factory(
+        cls, from_unit: str | None, to_unit: str | None
+    ) -> Callable[[float], float]:
+        """Return a function to convert one unit of measurement to another."""
+        ratio = cls._get_unit_ratio_or_raise(from_unit, to_unit)
+
+        def _converter(value: float) -> float:
+            return value / ratio
+
+        return _converter
+
+    @classmethod
+    @lru_cache(maxsize=128)
+    def converter_factory_allow_none(
+        cls, from_unit: str | None, to_unit: str | None
+    ) -> Callable[[float | None], float | None]:
+        """Return a function to convert one unit of measurement to another which allows None."""
+        ratio = cls._get_unit_ratio_or_raise(from_unit, to_unit)
+
+        def _converter_allow_none(value: float | None) -> float | None:
+            return None if value is None else value / ratio
+
+        return _converter_allow_none
+
+    @classmethod
+    def _get_unit_ratio_or_raise(
+        cls, from_unit: str | None, to_unit: str | None
+    ) -> float:
+        """Return the from_ratio and to_ratio for a unit conversion."""
         if from_unit == to_unit:
-            return value
+            return 1
 
         try:
             from_ratio = cls._UNIT_CONVERSION[from_unit]
@@ -84,8 +120,7 @@ def convert(cls, value: float, from_unit: str | None, to_unit: str | None) -> fl
                 UNIT_NOT_RECOGNIZED_TEMPLATE.format(to_unit, cls.UNIT_CLASS)
             ) from err
 
-        new_value = value / from_ratio
-        return new_value * to_ratio
+        return from_ratio / to_ratio
 
     @classmethod
     def get_unit_ratio(cls, from_unit: str | None, to_unit: str | None) -> float:
@@ -339,7 +374,42 @@ class TemperatureConverter(BaseUnitConverter):
     }
 
     @classmethod
-    def convert(cls, value: float, from_unit: str | None, to_unit: str | None) -> float:
+    @lru_cache(maxsize=16)
+    def converter_factory(
+        cls, from_unit: str | None, to_unit: str | None
+    ) -> Callable[[float], float]:
+        """Return a function to convert a temperature from one unit to another."""
+        if from_unit == to_unit:
+            # Return a function that does nothing. This is not
+            # in _converter_factory because we do not want to wrap
+            # it with the None check in converter_factory_allow_none.
+            return lambda value: value
+
+        return cls._converter_factory(from_unit, to_unit)
+
+    @classmethod
+    @lru_cache(maxsize=16)
+    def converter_factory_allow_none(
+        cls, from_unit: str | None, to_unit: str | None
+    ) -> Callable[[float | None], float | None]:
+        """Return a function to convert a temperature from one unit to another which allows None."""
+        if from_unit == to_unit:
+            # Return a function that does nothing. This is not
+            # in _converter_factory because we do not want to wrap
+            # it with the None check in this case.
+            return lambda value: value
+
+        convert = cls._converter_factory(from_unit, to_unit)
+
+        def _converter_allow_none(value: float | None) -> float | None:
+            return None if value is None else convert(value)
+
+        return _converter_allow_none
+
+    @classmethod
+    def _converter_factory(
+        cls, from_unit: str | None, to_unit: str | None
+    ) -> Callable[[float], float]:
         """Convert a temperature from one unit to another.
 
         eg. 10°C will return 50°F
@@ -349,32 +419,29 @@ def convert(cls, value: float, from_unit: str | None, to_unit: str | None) -> fl
         """
         # We cannot use the implementation from BaseUnitConverter here because the
         # temperature units do not use the same floor: 0°C, 0°F and 0K do not align
-        if from_unit == to_unit:
-            return value
-
         if from_unit == UnitOfTemperature.CELSIUS:
             if to_unit == UnitOfTemperature.FAHRENHEIT:
-                return cls._celsius_to_fahrenheit(value)
+                return cls._celsius_to_fahrenheit
             if to_unit == UnitOfTemperature.KELVIN:
-                return cls._celsius_to_kelvin(value)
+                return cls._celsius_to_kelvin
             raise HomeAssistantError(
                 UNIT_NOT_RECOGNIZED_TEMPLATE.format(to_unit, cls.UNIT_CLASS)
             )
 
         if from_unit == UnitOfTemperature.FAHRENHEIT:
             if to_unit == UnitOfTemperature.CELSIUS:
-                return cls._fahrenheit_to_celsius(value)
+                return cls._fahrenheit_to_celsius
             if to_unit == UnitOfTemperature.KELVIN:
-                return cls._celsius_to_kelvin(cls._fahrenheit_to_celsius(value))
+                return cls._fahrenheit_to_kelvin
             raise HomeAssistantError(
                 UNIT_NOT_RECOGNIZED_TEMPLATE.format(to_unit, cls.UNIT_CLASS)
             )
 
         if from_unit == UnitOfTemperature.KELVIN:
             if to_unit == UnitOfTemperature.CELSIUS:
-                return cls._kelvin_to_celsius(value)
+                return cls._kelvin_to_celsius
             if to_unit == UnitOfTemperature.FAHRENHEIT:
-                return cls._celsius_to_fahrenheit(cls._kelvin_to_celsius(value))
+                return cls._kelvin_to_fahrenheit
             raise HomeAssistantError(
                 UNIT_NOT_RECOGNIZED_TEMPLATE.format(to_unit, cls.UNIT_CLASS)
             )
@@ -393,7 +460,17 @@ def convert_interval(cls, interval: float, from_unit: str, to_unit: str) -> floa
         """
         # We use BaseUnitConverter implementation here because we are only interested
         # in the ratio between the units.
-        return super().convert(interval, from_unit, to_unit)
+        return super().converter_factory(from_unit, to_unit)(interval)
+
+    @classmethod
+    def _kelvin_to_fahrenheit(cls, kelvin: float) -> float:
+        """Convert a temperature in Kelvin to Fahrenheit."""
+        return (kelvin - 273.15) * 1.8 + 32.0
+
+    @classmethod
+    def _fahrenheit_to_kelvin(cls, fahrenheit: float) -> float:
+        """Convert a temperature in Fahrenheit to Kelvin."""
+        return 273.15 + ((fahrenheit - 32.0) / 1.8)
 
     @classmethod
     def _fahrenheit_to_celsius(cls, fahrenheit: float) -> float:

tests/components/recorder/test_websocket_api.py

@@ -1973,6 +1973,36 @@ async def test_change_statistics_unit(
         ],
     }
 
+    # Changing to the same unit is allowed but does nothing
+    await client.send_json(
+        {
+            "id": 6,
+            "type": "recorder/change_statistics_unit",
+            "statistic_id": "sensor.test",
+            "new_unit_of_measurement": "W",
+            "old_unit_of_measurement": "W",
+        }
+    )
+    response = await client.receive_json()
+    assert response["success"]
+    await async_recorder_block_till_done(hass)
+
+    await client.send_json({"id": 7, "type": "recorder/list_statistic_ids"})
+    response = await client.receive_json()
+    assert response["success"]
+    assert response["result"] == [
+        {
+            "statistic_id": "sensor.test",
+            "display_unit_of_measurement": "kW",
+            "has_mean": True,
+            "has_sum": False,
+            "name": None,
+            "source": "recorder",
+            "statistics_unit_of_measurement": "W",
+            "unit_class": "power",
+        }
+    ]
+
 
 async def test_change_statistics_unit_errors(
     recorder_mock: Recorder,

tests/util/test_unit_conversion.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import inspect
+from itertools import chain
 
 import pytest
 
@@ -534,6 +535,84 @@ def test_unit_conversion(
     assert converter.convert(value, from_unit, to_unit) == pytest.approx(expected)
 
 
+@pytest.mark.parametrize(
+    ("converter", "value", "from_unit", "expected", "to_unit"),
+    [
+        # Process all items in _CONVERTED_VALUE
+        (converter, value, from_unit, expected, to_unit)
+        for converter, item in _CONVERTED_VALUE.items()
+        for value, from_unit, expected, to_unit in item
+        if from_unit != to_unit
+    ],
+)
+def test_unit_conversion_factory(
+    converter: type[BaseUnitConverter],
+    value: float,
+    from_unit: str,
+    expected: float,
+    to_unit: str,
+) -> None:
+    """Test conversion to other units."""
+    assert converter.converter_factory(from_unit, to_unit)(value) == pytest.approx(
+        expected
+    )
+
+
+@pytest.mark.parametrize(
+    ("converter", "value", "from_unit", "expected", "to_unit"),
+    [
+        # Process all items in _CONVERTED_VALUE
+        (converter, value, from_unit, expected, to_unit)
+        for converter, item in _CONVERTED_VALUE.items()
+        for value, from_unit, expected, to_unit in item
+        if from_unit == to_unit
+    ],
+)
+def test_unit_conversion_factory_same_unit(
+    converter: type[BaseUnitConverter],
+    value: float,
+    from_unit: str,
+    expected: float,
+    to_unit: str,
+) -> None:
+    """Test conversion to same units."""
+    assert converter.converter_factory(from_unit, to_unit)(value) == pytest.approx(
+        expected
+    )
+
+
+@pytest.mark.parametrize(
+    ("converter", "value", "from_unit", "expected", "to_unit"),
+    chain(
+        [
+            # Process all items in _CONVERTED_VALUE
+            (converter, value, from_unit, expected, to_unit)
+            for converter, item in _CONVERTED_VALUE.items()
+            for value, from_unit, expected, to_unit in item
+            if from_unit != to_unit
+        ],
+        [
+            # Process all items in _CONVERTED_VALUE and replace the value with None
+            (converter, None, from_unit, None, to_unit)
+            for converter, item in _CONVERTED_VALUE.items()
+            for value, from_unit, expected, to_unit in item
+            if from_unit != to_unit
+        ],
+    ),
+)
+def test_unit_conversion_factory_allow_none(
+    converter: type[BaseUnitConverter],
+    value: float,
+    from_unit: str,
+    expected: float,
+    to_unit: str,
+) -> None:
+    """Test conversion to other units."""
+    assert converter.converter_factory_allow_none(from_unit, to_unit)(
+        value
+    ) == pytest.approx(expected)
+
+
 @pytest.mark.parametrize(
     ("value", "from_unit", "expected", "to_unit"),
     [