Add JSON attribute topic to MQTT binary sensor

Add MqttAttributes mixin

tests/components/binary_sensor/test_mqtt.py

@@ -1,7 +1,7 @@
 """The tests for the  MQTT binary sensor platform."""
 import json
 import unittest
-from unittest.mock import Mock
+from unittest.mock import Mock, patch
 from datetime import timedelta
 
 import homeassistant.core as ha
@@ -256,6 +256,67 @@ class TestSensorMQTT(unittest.TestCase):
         assert STATE_OFF == state.state
         assert 3 == len(events)
 
+    def test_setting_sensor_attribute_via_mqtt_json_message(self):
+        """Test the setting of attribute via MQTT with JSON payload."""
+        mock_component(self.hass, 'mqtt')
+        assert setup_component(self.hass, binary_sensor.DOMAIN, {
+            binary_sensor.DOMAIN: {
+                'platform': 'mqtt',
+                'name': 'test',
+                'state_topic': 'test-topic',
+                'json_attributes_topic': 'attr-topic'
+            }
+        })
+
+        fire_mqtt_message(self.hass, 'attr-topic', '{ "val": "100" }')
+        self.hass.block_till_done()
+        state = self.hass.states.get('binary_sensor.test')
+
+        assert '100' == \
+            state.attributes.get('val')
+
+    @patch('homeassistant.components.mqtt._LOGGER')
+    def test_update_with_json_attrs_not_dict(self, mock_logger):
+        """Test attributes get extracted from a JSON result."""
+        mock_component(self.hass, 'mqtt')
+        assert setup_component(self.hass, binary_sensor.DOMAIN, {
+            binary_sensor.DOMAIN: {
+                'platform': 'mqtt',
+                'name': 'test',
+                'state_topic': 'test-topic',
+                'json_attributes_topic': 'attr-topic'
+            }
+        })
+
+        fire_mqtt_message(self.hass, 'attr-topic', '[ "list", "of", "things"]')
+        self.hass.block_till_done()
+        state = self.hass.states.get('binary_sensor.test')
+
+        assert state.attributes.get('val') is None
+        mock_logger.debug.assert_called_with(
+            'JSON result was not a dictionary')
+
+    @patch('homeassistant.components.mqtt._LOGGER')
+    def test_update_with_json_attrs_bad_JSON(self, mock_logger):
+        """Test attributes get extracted from a JSON result."""
+        mock_component(self.hass, 'mqtt')
+        assert setup_component(self.hass, binary_sensor.DOMAIN, {
+            binary_sensor.DOMAIN: {
+                'platform': 'mqtt',
+                'name': 'test',
+                'state_topic': 'test-topic',
+                'json_attributes_topic': 'attr-topic'
+            }
+        })
+
+        fire_mqtt_message(self.hass, 'attr-topic', 'This is not JSON')
+        self.hass.block_till_done()
+
+        state = self.hass.states.get('binary_sensor.test')
+        assert state.attributes.get('val') is None
+        mock_logger.debug.assert_called_with(
+            'Erroneous JSON: %s', 'This is not JSON')
+
 
 async def test_unique_id(hass):
     """Test unique id option only creates one sensor per unique_id."""