Add available property to statistics component (#59203)

* Add available property to the statistics component

* Add test for statistics sensor availability

* Clean up availability check

* Improve statistics source sensor tests

* Revert variable rename

* Improve comments

homeassistant/components/statistics/sensor.py

@@ -126,6 +126,7 @@ class StatisticsSensor(SensorEntity):
         self._entity_id = entity_id
         self.is_binary = self._entity_id.split(".")[0] == "binary_sensor"
         self._name = name
+        self._available = False
         self._sampling_size = sampling_size
         self._max_age = max_age
         self._precision = precision
@@ -176,6 +177,7 @@ class StatisticsSensor(SensorEntity):
 
     def _add_state_to_queue(self, new_state):
         """Add the state to the queue."""
+        self._available = new_state.state != STATE_UNAVAILABLE
         if new_state.state in (STATE_UNKNOWN, STATE_UNAVAILABLE, None):
             return
 
@@ -184,7 +186,6 @@ class StatisticsSensor(SensorEntity):
                 self.states.append(new_state.state)
             else:
                 self.states.append(float(new_state.state))
-
             self.ages.append(new_state.last_updated)
         except ValueError:
             _LOGGER.error(
@@ -216,6 +217,11 @@ class StatisticsSensor(SensorEntity):
         """Return the unit the value is expressed in."""
         return self._unit_of_measurement if not self.is_binary else None
 
+    @property
+    def available(self):
+        """Return the availability of the sensor linked to the source sensor."""
+        return self._available
+
     @property
     def should_poll(self):
         """No polling needed."""

tests/components/statistics/test_sensor.py

@@ -12,6 +12,7 @@ from homeassistant.components.statistics.sensor import DOMAIN, StatisticsSensor
 from homeassistant.const import (
     ATTR_UNIT_OF_MEASUREMENT,
     SERVICE_RELOAD,
+    STATE_UNAVAILABLE,
     STATE_UNKNOWN,
     TEMP_CELSIUS,
 )
@@ -110,7 +111,6 @@ class TestStatisticsSensor(unittest.TestCase):
             self.hass.block_till_done()
 
         state = self.hass.states.get("sensor.test")
-
         assert str(self.mean) == state.state
         assert self.min == state.attributes.get("min_value")
         assert self.max == state.attributes.get("max_value")
@@ -125,13 +125,29 @@ class TestStatisticsSensor(unittest.TestCase):
         assert self.change == state.attributes.get("change")
         assert self.average_change == state.attributes.get("average_change")
 
-        # Source sensor is unavailable, unit and state should not change
+        # Source sensor turns unavailable, then available with valid value,
-        self.hass.states.set("sensor.test_monitored", "unavailable", {})
+        # statistics sensor should follow
+        state = self.hass.states.get("sensor.test")
+        self.hass.states.set(
+            "sensor.test_monitored",
+            STATE_UNAVAILABLE,
+            {ATTR_UNIT_OF_MEASUREMENT: TEMP_CELSIUS},
+        )
         self.hass.block_till_done()
         new_state = self.hass.states.get("sensor.test")
-        assert state == new_state
+        assert new_state.state == STATE_UNAVAILABLE
+        self.hass.states.set(
+            "sensor.test_monitored",
+            0,
+            {ATTR_UNIT_OF_MEASUREMENT: TEMP_CELSIUS},
+        )
+        self.hass.block_till_done()
+        new_state = self.hass.states.get("sensor.test")
+        assert new_state.state != STATE_UNAVAILABLE
+        assert new_state.attributes.get("count") == state.attributes.get("count") + 1
 
-        # Source sensor has a non float state, unit and state should not change
+        # Source sensor has a non-float state, unit and state should not change
+        state = self.hass.states.get("sensor.test")
         self.hass.states.set("sensor.test_monitored", "beer", {})
         self.hass.block_till_done()
         new_state = self.hass.states.get("sensor.test")