Define ToggleEntity entity attributes as class variables (#51231)

* Define ToggleEntity entity attributes as class variables

* Fix upcloud overriding state property

* Implement available state for upcloud, to compensate removed state

homeassistant/components/upcloud/__init__.py

@@ -273,18 +273,20 @@ class UpCloudServerEntity(CoordinatorEntity):
         """Return the icon of this server."""
         return "mdi:server" if self.is_on else "mdi:server-off"
 
-    @property
-    def state(self) -> str | None:
-        """Return state of the server."""
-        try:
-            return STATE_MAP.get(self._server.state, self._server.state)
-        except AttributeError:
-            return None
-
     @property
     def is_on(self) -> bool:
         """Return true if the server is on."""
-        return self.state == STATE_ON
+        try:
+            return STATE_MAP.get(self._server.state, self._server.state) == STATE_ON
+        except AttributeError:
+            return False
+
+    @property
+    def available(self) -> bool:
+        """Return True if entity is available."""
+        return super().available and STATE_MAP.get(
+            self._server.state, self._server.state
+        ) in [STATE_ON, STATE_OFF]
 
     @property
     def extra_state_attributes(self) -> dict[str, Any]:

homeassistant/helpers/entity.py

@@ -10,7 +10,7 @@ import logging
 import math
 import sys
 from timeit import default_timer as timer
-from typing import Any, TypedDict
+from typing import Any, TypedDict, final
 
 from homeassistant.config import DATA_CUSTOMIZE
 from homeassistant.const import (
@@ -766,7 +766,11 @@ class Entity(ABC):
 class ToggleEntity(Entity):
     """An abstract class for entities that can be turned on and off."""
 
+    _attr_is_on: bool
+    _attr_state: None = None
+
     @property
+    @final
     def state(self) -> str | None:
         """Return the state."""
         return STATE_ON if self.is_on else STATE_OFF
@@ -774,7 +778,7 @@ class ToggleEntity(Entity):
     @property
     def is_on(self) -> bool:
         """Return True if entity is on."""
-        raise NotImplementedError()
+        return self._attr_is_on
 
     def turn_on(self, **kwargs: Any) -> None:
         """Turn the entity on."""