Added support for extracting JSON attributes from RESTful values

Setting the json_attributes configuration option to true on the
RESTful sensor will cause the result of the REST request to be parsed
as a JSON string and if successful the resulting dictionary will be
used for the attributes of the sensor.

homeassistant/components/sensor/rest.py

@@ -5,6 +5,7 @@
 https://home-assistant.io/components/sensor.rest/
 """
 import logging
+import json
 
 import voluptuous as vol
 import requests
@@ -25,6 +26,8 @@
 DEFAULT_NAME = 'REST Sensor'
 DEFAULT_VERIFY_SSL = True
 
+CONF_JSON_ATTRS = "json_attributes"
+
 PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
     vol.Required(CONF_RESOURCE): cv.url,
     vol.Optional(CONF_AUTHENTICATION):
@@ -38,6 +41,7 @@
     vol.Optional(CONF_USERNAME): cv.string,
     vol.Optional(CONF_VALUE_TEMPLATE): cv.template,
     vol.Optional(CONF_VERIFY_SSL, default=DEFAULT_VERIFY_SSL): cv.boolean,
+    vol.Optional(CONF_JSON_ATTRS): cv.boolean,
 })
 
 
@@ -53,6 +57,7 @@ def setup_platform(hass, config, add_devices, discovery_info=None):
     headers = config.get(CONF_HEADERS)
     unit = config.get(CONF_UNIT_OF_MEASUREMENT)
     value_template = config.get(CONF_VALUE_TEMPLATE)
+    json_attrs = config.get(CONF_JSON_ATTRS)
     if value_template is not None:
         value_template.hass = hass
 
@@ -70,20 +75,24 @@ def setup_platform(hass, config, add_devices, discovery_info=None):
         _LOGGER.error("Unable to fetch REST data")
         return False
 
-    add_devices([RestSensor(hass, rest, name, unit, value_template)])
+    add_devices([RestSensor(hass, rest, name, unit,
+                            value_template, json_attrs)])
 
 
 class RestSensor(Entity):
     """Implementation of a REST sensor."""
 
-    def __init__(self, hass, rest, name, unit_of_measurement, value_template):
+    def __init__(self, hass, rest, name,
+                 unit_of_measurement, value_template, json_attrs):
         """Initialize the REST sensor."""
         self._hass = hass
         self.rest = rest
         self._name = name
         self._state = STATE_UNKNOWN
         self._unit_of_measurement = unit_of_measurement
         self._value_template = value_template
+        self._json_attrs = json_attrs
+        self._attributes = None
         self.update()
 
     @property
@@ -112,8 +121,21 @@ def update(self):
             value = self._value_template.render_with_possible_json_value(
                 value, STATE_UNKNOWN)
 
+        if self._json_attrs:
+            self._attributes = None
+            try:
+                self._attributes = json.loads(value)
+            except ValueError:
+                _LOGGER.warning('REST result could not be parsed as JSON')
+                _LOGGER.debug('Erroneous JSON: %s', value)
+
         self._state = value
 
+    @property
+    def device_state_attributes(self):
+        """Return the state attributes."""
+        return self._attributes
+
 
 class RestData(object):
     """Class for handling the data retrieval."""

tests/components/sensor/test_rest.py

@@ -135,7 +135,7 @@ def setUp(self):
 
         self.sensor = rest.RestSensor(self.hass, self.rest, self.name,
                                       self.unit_of_measurement,
-                                      self.value_template)
+                                      self.value_template, False)
 
     def tearDown(self):
         """Stop everything that was started."""
@@ -179,10 +179,21 @@ def test_update_with_no_template(self):
                                 side_effect=self.update_side_effect(
                                     'plain_state'))
         self.sensor = rest.RestSensor(self.hass, self.rest, self.name,
-                                      self.unit_of_measurement, None)
+                                      self.unit_of_measurement, None, False)
         self.sensor.update()
         self.assertEqual('plain_state', self.sensor.state)
 
+    def test_update_with_josn_attrs(self):
+        """Test attributes get extracted from a JSON result."""
+        self.rest.update = Mock('rest.RestData.update',
+                                side_effect=self.update_side_effect(
+                                    '{ "key": "updated_state" }'))
+        self.sensor = rest.RestSensor(self.hass, self.rest, self.name,
+                                      self.unit_of_measurement, None, True)
+        self.sensor.update()
+        self.assertEqual('updated_state',
+                         self.sensor.device_state_attributes.key)
+
 
 class TestRestData(unittest.TestCase):
     """Tests for RestData."""