Adding expire_after to mqtt sensor to expire outdated values (#6708)

* Adding expire_after to mqtt sensor to expire outdated values

* Extending test case

* mqtt: refactoring expire_after to use timed events instead of polling; lint

* refactor to reset unused trigger

* Fix: handler must be set to None after execution or removal to avoid warning

* Commenting out non-working test

* Fix lint

* Commit to trigger new build

* Commit to trigger new build

* Make testcase work

* Undo unnecessary change

* Remove default value, add extra check

tests/components/sensor/test_mqtt.py

@@ -1,12 +1,16 @@
 """The tests for the MQTT sensor platform."""
 import unittest
 
+from datetime import timedelta, datetime
+from unittest.mock import patch
+
 import homeassistant.core as ha
 from homeassistant.setup import setup_component
 import homeassistant.components.sensor as sensor
 from homeassistant.const import EVENT_STATE_CHANGED
-from tests.common import mock_mqtt_component, fire_mqtt_message
+import homeassistant.util.dt as dt_util
 
+from tests.common import mock_mqtt_component, fire_mqtt_message
 from tests.common import get_test_home_assistant, mock_component
 
 
@@ -42,6 +46,69 @@ class TestSensorMQTT(unittest.TestCase):
         self.assertEqual('fav unit',
                          state.attributes.get('unit_of_measurement'))
 
+    @patch('homeassistant.core.dt_util.utcnow')
+    def test_setting_sensor_value_expires(self, mock_utcnow):
+        """Test the expiration of the value."""
+        mock_component(self.hass, 'mqtt')
+        assert setup_component(self.hass, sensor.DOMAIN, {
+            sensor.DOMAIN: {
+                'platform': 'mqtt',
+                'name': 'test',
+                'state_topic': 'test-topic',
+                'unit_of_measurement': 'fav unit',
+                'expire_after': '4',
+                'force_update': True
+            }
+        })
+
+        state = self.hass.states.get('sensor.test')
+        self.assertEqual('unknown', state.state)
+
+        now = datetime(2017, 1, 1, 1, tzinfo=dt_util.UTC)
+        mock_utcnow.return_value = now
+        fire_mqtt_message(self.hass, 'test-topic', '100')
+        self.hass.block_till_done()
+
+        # Value was set correctly.
+        state = self.hass.states.get('sensor.test')
+        self.assertEqual('100', state.state)
+
+        # Time jump +3s
+        now = now + timedelta(seconds=3)
+        self._send_time_changed(now)
+        self.hass.block_till_done()
+
+        # Value is not yet expired
+        state = self.hass.states.get('sensor.test')
+        self.assertEqual('100', state.state)
+
+        # Next message resets timer
+        mock_utcnow.return_value = now
+        fire_mqtt_message(self.hass, 'test-topic', '101')
+        self.hass.block_till_done()
+
+        # Value was updated correctly.
+        state = self.hass.states.get('sensor.test')
+        self.assertEqual('101', state.state)
+
+        # Time jump +3s
+        now = now + timedelta(seconds=3)
+        self._send_time_changed(now)
+        self.hass.block_till_done()
+
+        # Value is not yet expired
+        state = self.hass.states.get('sensor.test')
+        self.assertEqual('101', state.state)
+
+        # Time jump +2s
+        now = now + timedelta(seconds=2)
+        self._send_time_changed(now)
+        self.hass.block_till_done()
+
+        # Value is expired now
+        state = self.hass.states.get('sensor.test')
+        self.assertEqual('unknown', state.state)
+
     def test_setting_sensor_value_via_mqtt_json_message(self):
         """Test the setting of the value via MQTT with JSON playload."""
         mock_component(self.hass, 'mqtt')
@@ -117,3 +184,7 @@ class TestSensorMQTT(unittest.TestCase):
         fire_mqtt_message(self.hass, 'test-topic', '100')
         self.hass.block_till_done()
         self.assertEqual(2, len(events))
+
+    def _send_time_changed(self, now):
+        """Send a time changed event."""
+        self.hass.bus.fire(ha.EVENT_TIME_CHANGED, {ha.ATTR_NOW: now})