Don't initialize mqtt components which have already been discovered (#7625)

* Don't initialize mqtt components which have already been discovered

* Fix string length

* Fix blank lines, fix constant name

* Remove globals. Remove JSON dump

* Add tests. Update grammar

* PEP8 style issue

* Add hyphen to object_id regex

* PEP8 style fix

homeassistant/components/mqtt/discovery.py

@@ -17,7 +17,8 @@ from homeassistant.components.mqtt import CONF_STATE_TOPIC
 _LOGGER = logging.getLogger(__name__)
 
 TOPIC_MATCHER = re.compile(
-    r'(?P<prefix_topic>\w+)/(?P<component>\w+)/(?P<object_id>\w+)/config')
+    r'(?P<prefix_topic>\w+)/(?P<component>\w+)/(?P<object_id>[a-zA-Z0-9_-]+)'
+    '/config')
 
 SUPPORTED_COMPONENTS = ['binary_sensor', 'light', 'sensor', 'switch']
 
@@ -28,6 +29,8 @@ ALLOWED_PLATFORMS = {
     'switch': ['mqtt'],
 }
 
+ALREADY_DISCOVERED = 'mqtt_discovered_components'
+
 
 @asyncio.coroutine
 def async_start(hass, discovery_topic, hass_config):
@@ -65,6 +68,19 @@ def async_start(hass, discovery_topic, hass_config):
             payload[CONF_STATE_TOPIC] = '{}/{}/{}/state'.format(
                 discovery_topic, component, object_id)
 
+        if ALREADY_DISCOVERED not in hass.data:
+            hass.data[ALREADY_DISCOVERED] = set()
+
+        discovery_hash = (component, object_id)
+        if discovery_hash in hass.data[ALREADY_DISCOVERED]:
+            _LOGGER.info("Component has already been discovered: %s %s",
+                         component, object_id)
+            return
+
+        hass.data[ALREADY_DISCOVERED].add(discovery_hash)
+
+        _LOGGER.info("Found new component: %s %s", component, object_id)
+
         yield from async_load_platform(
             hass, component, platform, payload, hass_config)
 

tests/components/mqtt/test_discovery.py

@@ -73,3 +73,24 @@ def test_correct_config_discovery(hass, mqtt_mock, caplog):
 
     assert state is not None
     assert state.name == 'Beer'
+
+
+@asyncio.coroutine
+def test_non_duplicate_discovery(hass, mqtt_mock, caplog):
+    """Test for a non duplicate component."""
+    yield from async_start(hass, 'homeassistant', {})
+
+    async_fire_mqtt_message(hass, 'homeassistant/binary_sensor/bla/config',
+                            '{ "name": "Beer" }')
+    async_fire_mqtt_message(hass, 'homeassistant/binary_sensor/bla/config',
+                            '{ "name": "Beer" }')
+    yield from hass.async_block_till_done()
+
+    state = hass.states.get('binary_sensor.beer')
+    state_duplicate = hass.states.get('binary_sensor.beer1')
+
+    assert state is not None
+    assert state.name == 'Beer'
+    assert state_duplicate is None
+    assert 'Component has already been discovered: ' \
+           'binary_sensor bla' in caplog.text