Fix RFLink restore state (#20588)

* some minor tests refactor

* unused import

* async/await refactor

* Correct tests failures

* Restore state bug
added call to super().async_added_to_hass()

* Show brightness attribute if device supports it

* Fix light/test_rflink 

Dimmable devices defaults to 255 brightness

* delete super().device_state_attributes call

homeassistant/components/light/rflink.py

@@ -185,6 +185,14 @@ class DimmableRflinkLight(SwitchableRflinkDevice, Light):
         """Return the brightness of this light between 0..255."""
         return self._brightness
 
+    @property
+    def device_state_attributes(self):
+        """Return the device state attributes."""
+        attr = {}
+        if self._brightness is not None:
+            attr[ATTR_BRIGHTNESS] = self._brightness
+        return attr
+
     @property
     def supported_features(self):
         """Flag supported features."""
@@ -239,6 +247,14 @@ class HybridRflinkLight(SwitchableRflinkDevice, Light):
         """Return the brightness of this light between 0..255."""
         return self._brightness
 
+    @property
+    def device_state_attributes(self):
+        """Return the device state attributes."""
+        attr = {}
+        if self._brightness is not None:
+            attr[ATTR_BRIGHTNESS] = self._brightness
+        return attr
+
     @property
     def supported_features(self):
         """Flag supported features."""

homeassistant/components/rflink/__init__.py

@@ -345,6 +345,7 @@ class RflinkDevice(Entity):
 
     async def async_added_to_hass(self):
         """Register update callback."""
+        await super().async_added_to_hass()
         # Remove temporary bogus entity_id if added
         tmp_entity = TMP_ENTITY.format(self._device_id)
         if tmp_entity in self.hass.data[DATA_ENTITY_LOOKUP][

tests/components/light/test_rflink.py

@@ -632,7 +632,7 @@ async def test_restore_state(hass, monkeypatch):
     state = hass.states.get(DOMAIN + '.l4')
     assert state
     assert state.state == STATE_OFF
-    assert not state.attributes.get(ATTR_BRIGHTNESS)
+    assert state.attributes[ATTR_BRIGHTNESS] == 255
     assert state.attributes['assumed_state']
 
     # test coverage for dimmable light