Add json_attributes_template (#22981)

homeassistant/components/mqtt/__init__.py

@@ -69,6 +69,7 @@ CONF_AVAILABILITY_TOPIC = 'availability_topic'
 CONF_PAYLOAD_AVAILABLE = 'payload_available'
 CONF_PAYLOAD_NOT_AVAILABLE = 'payload_not_available'
 CONF_JSON_ATTRS_TOPIC = 'json_attributes_topic'
+CONF_JSON_ATTRS_TEMPLATE = 'json_attributes_template'
 CONF_QOS = 'qos'
 CONF_RETAIN = 'retain'
 
@@ -242,6 +243,7 @@ MQTT_ENTITY_DEVICE_INFO_SCHEMA = vol.All(vol.Schema({
 
 MQTT_JSON_ATTRS_SCHEMA = vol.Schema({
     vol.Optional(CONF_JSON_ATTRS_TOPIC): valid_subscribe_topic,
+    vol.Optional(CONF_JSON_ATTRS_TEMPLATE): cv.template,
 })
 
 MQTT_BASE_PLATFORM_SCHEMA = cv.PLATFORM_SCHEMA.extend(SCHEMA_BASE)
@@ -908,10 +910,18 @@ class MqttAttributes(Entity):
         """(Re)Subscribe to topics."""
         from .subscription import async_subscribe_topics
 
+        attr_tpl = self._attributes_config.get(CONF_JSON_ATTRS_TEMPLATE)
+        if attr_tpl is not None:
+            attr_tpl.hass = self.hass
+
         @callback
         def attributes_message_received(msg: Message) -> None:
             try:
-                json_dict = json.loads(msg.payload)
+                payload = msg.payload
+                if attr_tpl is not None:
+                    payload = attr_tpl.async_render_with_possible_json_value(
+                        payload)
+                json_dict = json.loads(payload)
                 if isinstance(json_dict, dict):
                     self._attributes = json_dict
                     self.async_write_ha_state()
@@ -919,7 +929,7 @@ class MqttAttributes(Entity):
                     _LOGGER.warning("JSON result was not a dictionary")
                     self._attributes = None
             except ValueError:
-                _LOGGER.warning("Erroneous JSON: %s", msg.payload)
+                _LOGGER.warning("Erroneous JSON: %s", payload)
                 self._attributes = None
 
         self._attributes_sub_state = await async_subscribe_topics(

tests/components/mqtt/test_sensor.py

@@ -384,6 +384,27 @@ async def test_setting_attribute_via_mqtt_json_message(hass, mqtt_mock):
     assert '100' == state.attributes.get('val')
 
 
+async def test_setting_attribute_with_template(hass, mqtt_mock):
+    """Test the setting of attribute via MQTT with JSON payload."""
+    assert await async_setup_component(hass, sensor.DOMAIN, {
+        sensor.DOMAIN: {
+            'platform': 'mqtt',
+            'name': 'test',
+            'state_topic': 'test-topic',
+            'json_attributes_topic': 'attr-topic',
+            'json_attributes_template': "{{ value_json['Timer1'] | tojson }}"
+        }
+    })
+
+    async_fire_mqtt_message(hass, 'attr-topic', json.dumps(
+        {"Timer1": {"Arm": 0, "Time": "22:18"}}))
+    await hass.async_block_till_done()
+    state = hass.states.get('sensor.test')
+
+    assert 0 == state.attributes.get('Arm')
+    assert '22:18' == state.attributes.get('Time')
+
+
 async def test_update_with_json_attrs_not_dict(hass, mqtt_mock, caplog):
     """Test attributes get extracted from a JSON result."""
     assert await async_setup_component(hass, sensor.DOMAIN, {