Added mqtt_statestream component (#9286)

* Added mqtt_statestream component

* Added tests for mqtt_statestream component

* mqtt_statestream: add test for valid new_state

* mqtt_statestream: Don't set initialized state

* mqtt_statestream: Switch to using async_track_state_change

* Cleanup

homeassistant/components/mqtt_statestream.py

@@ -0,0 +1,45 @@
+"""
+Publish simple item state changes via MQTT.
+
+For more details about this component, please refer to the documentation at
+https://home-assistant.io/components/mqtt_statestream/
+"""
+import asyncio
+
+import voluptuous as vol
+
+from homeassistant.const import MATCH_ALL
+from homeassistant.core import callback
+from homeassistant.components.mqtt import valid_publish_topic
+from homeassistant.helpers.event import async_track_state_change
+
+CONF_BASE_TOPIC = 'base_topic'
+DEPENDENCIES = ['mqtt']
+DOMAIN = 'mqtt_statestream'
+
+CONFIG_SCHEMA = vol.Schema({
+    DOMAIN: vol.Schema({
+        vol.Required(CONF_BASE_TOPIC): valid_publish_topic
+    })
+}, extra=vol.ALLOW_EXTRA)
+
+
+@asyncio.coroutine
+def async_setup(hass, config):
+    """Set up the MQTT state feed."""
+    conf = config.get(DOMAIN, {})
+    base_topic = conf.get(CONF_BASE_TOPIC)
+    if not base_topic.endswith('/'):
+        base_topic = base_topic + '/'
+
+    @callback
+    def _state_publisher(entity_id, old_state, new_state):
+        if new_state is None:
+            return
+        payload = new_state.state
+
+        topic = base_topic + entity_id.replace('.', '/')
+        hass.components.mqtt.async_publish(topic, payload, 1, True)
+
+    async_track_state_change(hass, MATCH_ALL, _state_publisher)
+    return True

tests/components/test_mqtt_statestream.py

@@ -0,0 +1,65 @@
+"""The tests for the MQTT statestream component."""
+from unittest.mock import patch
+
+from homeassistant.setup import setup_component
+import homeassistant.components.mqtt_statestream as statestream
+from homeassistant.core import State
+
+from tests.common import (
+    get_test_home_assistant,
+    mock_mqtt_component,
+    mock_state_change_event
+)
+
+
+class TestMqttStateStream(object):
+    """Test the MQTT statestream module."""
+
+    def setup_method(self):
+        """Setup things to be run when tests are started."""
+        self.hass = get_test_home_assistant()
+        self.mock_mqtt = mock_mqtt_component(self.hass)
+
+    def teardown_method(self):
+        """Stop everything that was started."""
+        self.hass.stop()
+
+    def add_statestream(self, base_topic=None):
+        """Add a mqtt_statestream component."""
+        config = {}
+        if base_topic:
+            config['base_topic'] = base_topic
+        return setup_component(self.hass, statestream.DOMAIN, {
+            statestream.DOMAIN: config})
+
+    def test_fails_with_no_base(self):
+        """Setup should fail if no base_topic is set."""
+        assert self.add_statestream() is False
+
+    def test_setup_succeeds(self):
+        """"Test the success of the setup with a valid base_topic."""
+        assert self.add_statestream(base_topic='pub')
+
+    @patch('homeassistant.components.mqtt.async_publish')
+    @patch('homeassistant.core.dt_util.utcnow')
+    def test_state_changed_event_sends_message(self, mock_utcnow, mock_pub):
+        """"Test the sending of a new message if event changed."""
+        e_id = 'fake.entity'
+        base_topic = 'pub'
+
+        # Add the statestream component for publishing state updates
+        assert self.add_statestream(base_topic=base_topic)
+        self.hass.block_till_done()
+
+        # Reset the mock because it will have already gotten calls for the
+        # mqtt_statestream state change on initialization, etc.
+        mock_pub.reset_mock()
+
+        # Set a state of an entity
+        mock_state_change_event(self.hass, State(e_id, 'on'))
+        self.hass.block_till_done()
+
+        # Make sure 'on' was published to pub/fake/entity
+        mock_pub.assert_called_with(self.hass, 'pub/fake/entity', 'on', 1,
+                                    True)
+        assert mock_pub.called