Support value_template in MQTT triggers (#46891)

* Support value_template in MQTT triggers

* Rename value_template to payload_template

* Revert "Rename value_template to payload_template"

This reverts commit 902094eefc6612e6b5c3bdb7440520af050c7f20.

homeassistant/components/mqtt/trigger.py

@@ -4,7 +4,7 @@ import logging
 
 import voluptuous as vol
 
-from homeassistant.const import CONF_PAYLOAD, CONF_PLATFORM
+from homeassistant.const import CONF_PAYLOAD, CONF_PLATFORM, CONF_VALUE_TEMPLATE
 from homeassistant.core import HassJob, callback
 from homeassistant.helpers import config_validation as cv, template
 
@@ -23,6 +23,7 @@ TRIGGER_SCHEMA = vol.Schema(
         vol.Required(CONF_PLATFORM): mqtt.DOMAIN,
         vol.Required(CONF_TOPIC): mqtt.util.valid_subscribe_topic_template,
         vol.Optional(CONF_PAYLOAD): cv.template,
+        vol.Optional(CONF_VALUE_TEMPLATE): cv.template,
         vol.Optional(CONF_ENCODING, default=DEFAULT_ENCODING): cv.string,
         vol.Optional(CONF_QOS, default=DEFAULT_QOS): vol.All(
             vol.Coerce(int), vol.In([0, 1, 2])
@@ -36,7 +37,8 @@ _LOGGER = logging.getLogger(__name__)
 async def async_attach_trigger(hass, config, action, automation_info):
     """Listen for state changes based on configuration."""
     topic = config[CONF_TOPIC]
-    payload = config.get(CONF_PAYLOAD)
+    wanted_payload = config.get(CONF_PAYLOAD)
+    value_template = config.get(CONF_VALUE_TEMPLATE)
     encoding = config[CONF_ENCODING] or None
     qos = config[CONF_QOS]
     job = HassJob(action)
@@ -44,19 +46,29 @@ async def async_attach_trigger(hass, config, action, automation_info):
     if automation_info:
         variables = automation_info.get("variables")
 
-    template.attach(hass, payload)
-    if payload:
-        payload = payload.async_render(variables, limited=True)
+    template.attach(hass, wanted_payload)
+    if wanted_payload:
+        wanted_payload = wanted_payload.async_render(variables, limited=True)
 
     template.attach(hass, topic)
     if isinstance(topic, template.Template):
         topic = topic.async_render(variables, limited=True)
         topic = mqtt.util.valid_subscribe_topic(topic)
 
+    template.attach(hass, value_template)
+
     @callback
     def mqtt_automation_listener(mqttmsg):
         """Listen for MQTT messages."""
-        if payload is None or payload == mqttmsg.payload:
+        payload = mqttmsg.payload
+
+        if value_template is not None:
+            payload = value_template.async_render_with_possible_json_value(
+                payload,
+                error_value=None,
+            )
+
+        if wanted_payload is None or wanted_payload == payload:
             data = {
                 "platform": "mqtt",
                 "topic": mqttmsg.topic,
@@ -73,7 +85,7 @@ async def async_attach_trigger(hass, config, action, automation_info):
             hass.async_run_hass_job(job, {"trigger": data})
 
     _LOGGER.debug(
-        "Attaching MQTT trigger for topic: '%s', payload: '%s'", topic, payload
+        "Attaching MQTT trigger for topic: '%s', payload: '%s'", topic, wanted_payload
     )
 
     remove = await mqtt.async_subscribe(

tests/components/mqtt/test_trigger.py

@@ -111,6 +111,37 @@ async def test_if_fires_on_templated_topic_and_payload_match(hass, calls):
     assert len(calls) == 1
 
 
+async def test_if_fires_on_payload_template(hass, calls):
+    """Test if message is fired on templated topic and payload match."""
+    assert await async_setup_component(
+        hass,
+        automation.DOMAIN,
+        {
+            automation.DOMAIN: {
+                "trigger": {
+                    "platform": "mqtt",
+                    "topic": "test-topic",
+                    "payload": "hello",
+                    "value_template": "{{ value_json.wanted_key }}",
+                },
+                "action": {"service": "test.automation"},
+            }
+        },
+    )
+
+    async_fire_mqtt_message(hass, "test-topic", "hello")
+    await hass.async_block_till_done()
+    assert len(calls) == 0
+
+    async_fire_mqtt_message(hass, "test-topic", '{"unwanted_key":"hello"}')
+    await hass.async_block_till_done()
+    assert len(calls) == 0
+
+    async_fire_mqtt_message(hass, "test-topic", '{"wanted_key":"hello"}')
+    await hass.async_block_till_done()
+    assert len(calls) == 1
+
+
 async def test_non_allowed_templates(hass, calls, caplog):
     """Test non allowed function in template."""
     assert await async_setup_component(