Adding expire_after to mqtt sensor to expire outdated values (#6708)

* Adding expire_after to mqtt sensor to expire outdated values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

homeassistant/components/sensor/mqtt.py

@@ -6,6 +6,7 @@ https://home-assistant.io/components/sensor.mqtt/
 """
 import asyncio
 import logging
+from datetime import timedelta
 
 import voluptuous as vol
 
@@ -16,10 +17,13 @@ from homeassistant.const import (
 from homeassistant.helpers.entity import Entity
 import homeassistant.components.mqtt as mqtt
 import homeassistant.helpers.config_validation as cv
+from homeassistant.helpers.event import async_track_point_in_utc_time
+from homeassistant.util import dt as dt_util
 
 _LOGGER = logging.getLogger(__name__)
 
 CONF_FORCE_UPDATE = 'force_update'
+CONF_EXPIRE_AFTER = 'expire_after'
 
 DEFAULT_NAME = 'MQTT Sensor'
 DEFAULT_FORCE_UPDATE = False
@@ -28,6 +32,7 @@ DEPENDENCIES = ['mqtt']
 PLATFORM_SCHEMA = mqtt.MQTT_RO_PLATFORM_SCHEMA.extend({
     vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
     vol.Optional(CONF_UNIT_OF_MEASUREMENT): cv.string,
+    vol.Optional(CONF_EXPIRE_AFTER): cv.positive_int,
     vol.Optional(CONF_FORCE_UPDATE, default=DEFAULT_FORCE_UPDATE): cv.boolean,
 })
 
@@ -48,6 +53,7 @@ def async_setup_platform(hass, config, async_add_devices, discovery_info=None):
         config.get(CONF_QOS),
         config.get(CONF_UNIT_OF_MEASUREMENT),
         config.get(CONF_FORCE_UPDATE),
+        config.get(CONF_EXPIRE_AFTER),
         value_template,
     )])
 
@@ -56,7 +62,7 @@ class MqttSensor(Entity):
     """Representation of a sensor that can be updated using MQTT."""
 
     def __init__(self, name, state_topic, qos, unit_of_measurement,
-                 force_update, value_template):
+                 force_update, expire_after, value_template):
         """Initialize the sensor."""
         self._state = STATE_UNKNOWN
         self._name = name
@@ -65,6 +71,8 @@ class MqttSensor(Entity):
         self._unit_of_measurement = unit_of_measurement
         self._force_update = force_update
         self._template = value_template
+        self._expire_after = expire_after
+        self._expiration_trigger = None
 
     def async_added_to_hass(self):
         """Subscribe mqtt events.
@@ -74,6 +82,22 @@ class MqttSensor(Entity):
         @callback
         def message_received(topic, payload, qos):
             """A new MQTT message has been received."""
+            # auto-expire enabled?
+            if self._expire_after is not None and self._expire_after > 0:
+                # Reset old trigger
+                if self._expiration_trigger:
+                    self._expiration_trigger()
+                    self._expiration_trigger = None
+
+                # Set new trigger
+                expiration_at = (
+                    dt_util.utcnow() + timedelta(seconds=self._expire_after))
+
+                self._expiration_trigger = async_track_point_in_utc_time(
+                    self.hass,
+                    self.value_is_expired,
+                    expiration_at)
+
             if self._template is not None:
                 payload = self._template.async_render_with_possible_json_value(
                     payload, self._state)
@@ -83,6 +107,13 @@ class MqttSensor(Entity):
         return mqtt.async_subscribe(
             self.hass, self._state_topic, message_received, self._qos)
 
+    @callback
+    def value_is_expired(self, *_):
+        """Triggered when value is expired."""
+        self._expiration_trigger = None
+        self._state = STATE_UNKNOWN
+        self.hass.async_add_job(self.async_update_ha_state())
+
     @property
     def should_poll(self):
         """No polling needed."""

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})