Restore speed when turning a Tasmota fan back on (home-assistant#84337)

homeassistant/components/tasmota/fan.py

@@ -65,6 +65,7 @@ class TasmotaFan(
     """Representation of a Tasmota fan."""
 
     _attr_supported_features = FanEntityFeature.SET_SPEED
+    _fan_speed = tasmota_const.FAN_SPEED_MEDIUM
     _tasmota_entity: tasmota_fan.TasmotaFan
 
     def __init__(self, **kwds: Any) -> None:
@@ -84,6 +85,9 @@ async def async_added_to_hass(self) -> None:
     def fan_state_updated(self, state: int, **kwargs: Any) -> None:
         """Handle state updates."""
         self._state = state
+        if self._state is not None and self._state != 0:
+            # Store the last known fan speed
+            self._fan_speed = state
         self.async_write_ha_state()
 
     @property
@@ -121,7 +125,7 @@ async def async_turn_on(
         await self.async_set_percentage(
             percentage
             or ordered_list_item_to_percentage(
-                ORDERED_NAMED_FAN_SPEEDS, tasmota_const.FAN_SPEED_MEDIUM
+                ORDERED_NAMED_FAN_SPEEDS, self._fan_speed
             )
         )
 

tests/components/tasmota/test_fan.py

@@ -154,6 +154,33 @@ async def test_sending_mqtt_commands(hass, mqtt_mock, setup_tasmota):
         "tasmota_49A3BC/cmnd/FanSpeed", "3", 0, False
     )
 
+    # Test the last known fan speed is restored
+    # First, get a fan speed update
+    async_fire_mqtt_message(hass, "tasmota_49A3BC/tele/STATE", '{"FanSpeed":3}')
+    state = hass.states.get("fan.tasmota")
+    assert state.state == STATE_ON
+    assert state.attributes["percentage"] == 100
+    mqtt_mock.async_publish.reset_mock()
+
+    # Then turn the fan off and get a fan state update
+    await common.async_turn_off(hass, "fan.tasmota")
+    mqtt_mock.async_publish.assert_called_once_with(
+        "tasmota_49A3BC/cmnd/FanSpeed", "0", 0, False
+    )
+    mqtt_mock.async_publish.reset_mock()
+    async_fire_mqtt_message(hass, "tasmota_49A3BC/stat/RESULT", '{"FanSpeed":0}')
+    state = hass.states.get("fan.tasmota")
+    assert state.state == STATE_OFF
+    assert state.attributes["percentage"] == 0
+    mqtt_mock.async_publish.reset_mock()
+
+    # Finally, turn the fan on again and verify MQTT message is sent with last known speed
+    await common.async_turn_on(hass, "fan.tasmota")
+    mqtt_mock.async_publish.assert_called_once_with(
+        "tasmota_49A3BC/cmnd/FanSpeed", "3", 0, False
+    )
+    mqtt_mock.async_publish.reset_mock()
+
 
 async def test_invalid_fan_speed_percentage(hass, mqtt_mock, setup_tasmota):
     """Test the sending MQTT commands."""