Add precision_hint to feature (#871)

This can be used to hint how the sensor value should be rounded when
displaying it to users.

The values are adapted from the values used by homeassistant.

kasa/feature.py

@@ -79,6 +79,10 @@ class Feature:
     #: Type of the feature
     type: Feature.Type = Type.Sensor
 
+    # Display hints offer a way suggest how the value should be shown to users
+    #: Hint to help rounding the sensor values to given after-comma digits
+    precision_hint: int | None = None
+
     # Number-specific attributes
     #: Minimum value
     minimum_value: int = 0
@@ -151,7 +155,10 @@ class Feature:
         return await getattr(container, self.attribute_setter)(value)
 
     def __repr__(self):
-        s = f"{self.name} ({self.id}): {self.value}"
+        value = self.value
+        if self.precision_hint is not None and value is not None:
+            value = round(self.value, self.precision_hint)
+        s = f"{self.name} ({self.id}): {value}"
         if self.unit is not None:
             s += f" {self.unit}"
 

kasa/iot/modules/emeter.py

@@ -23,6 +23,7 @@ class Emeter(Usage):
                 container=self,
                 unit="W",
                 id="current_power_w",  # for homeassistant backwards compat
+                precision_hint=1,
             )
         )
         self._add_feature(
@@ -33,6 +34,7 @@ class Emeter(Usage):
                 container=self,
                 unit="kWh",
                 id="today_energy_kwh",  # for homeassistant backwards compat
+                precision_hint=3,
             )
         )
         self._add_feature(
@@ -42,6 +44,7 @@ class Emeter(Usage):
                 attribute_getter="emeter_this_month",
                 container=self,
                 unit="kWh",
+                precision_hint=3,
             )
         )
         self._add_feature(
@@ -52,6 +55,7 @@ class Emeter(Usage):
                 container=self,
                 unit="kWh",
                 id="total_energy_kwh",  # for homeassistant backwards compat
+                precision_hint=3,
             )
         )
         self._add_feature(
@@ -62,6 +66,7 @@ class Emeter(Usage):
                 container=self,
                 unit="V",
                 id="voltage",  # for homeassistant backwards compat
+                precision_hint=1,
             )
         )
         self._add_feature(
@@ -72,6 +77,7 @@ class Emeter(Usage):
                 container=self,
                 unit="A",
                 id="current_a",  # for homeassistant backwards compat
+                precision_hint=2,
             )
         )
 

kasa/smart/modules/energymodule.py

@@ -26,6 +26,7 @@ class EnergyModule(SmartModule):
                 attribute_getter="current_power",
                 container=self,
                 unit="W",
+                precision_hint=1,
             )
         )
         self._add_feature(
@@ -35,6 +36,7 @@ class EnergyModule(SmartModule):
                 attribute_getter="emeter_today",
                 container=self,
                 unit="Wh",
+                precision_hint=2,
             )
         )
         self._add_feature(
@@ -44,6 +46,7 @@ class EnergyModule(SmartModule):
                 attribute_getter="emeter_this_month",
                 container=self,
                 unit="Wh",
+                precision_hint=2,
             )
         )
 

kasa/tests/test_feature.py

@@ -108,3 +108,15 @@ async def test_feature_action(mocker):
     assert feat.value == "<Action>"
     await feat.set_value(1234)
     mock_call_action.assert_called()
+
+
+@pytest.mark.parametrize("precision_hint", [1, 2, 3])
+async def test_precision_hint(dummy_feature, precision_hint):
+    """Test that precision hint works as expected."""
+    dummy_value = 3.141593
+    dummy_feature.type = Feature.Type.Sensor
+    dummy_feature.precision_hint = precision_hint
+
+    dummy_feature.attribute_getter = lambda x: dummy_value
+    assert dummy_feature.value == dummy_value
+    assert f"{round(dummy_value, precision_hint)} dummyunit" in repr(dummy_feature)