MQTT Automation: parse payload as JSON (#4703)

homeassistant/components/automation/mqtt.py

@@ -4,6 +4,8 @@ Offer MQTT listening automation rules.
 For more details about this automation rule, please refer to the documentation
 at https://home-assistant.io/components/automation/#mqtt-trigger
 """
+import json
+
 import voluptuous as vol
 
 from homeassistant.core import callback
@@ -31,13 +33,20 @@ def async_trigger(hass, config, action):
     def mqtt_automation_listener(msg_topic, msg_payload, qos):
         """Listen for MQTT messages."""
         if payload is None or payload == msg_payload:
+            data = {
+                'platform': 'mqtt',
+                'topic': msg_topic,
+                'payload': msg_payload,
+                'qos': qos,
+            }
+
+            try:
+                data['payload_json'] = json.loads(msg_payload)
+            except ValueError:
+                pass
+
             hass.async_run_job(action, {
-                'trigger': {
-                    'platform': 'mqtt',
-                    'topic': msg_topic,
-                    'payload': msg_payload,
-                    'qos': qos,
-                }
+                'trigger': data
             })
 
     return mqtt.async_subscribe(hass, topic, mqtt_automation_listener)