Support empty output of MQTT binary_sensor value_template (#37420)

* Support empty output of MQTT binary_sensor value_template

* Strip white space

* Add test

* Add test

homeassistant/components/mqtt/binary_sensor.py

@@ -189,17 +189,30 @@ class MqttBinarySensor(
                 payload = value_template.async_render_with_possible_json_value(
                     payload, variables={"entity_id": self.entity_id}
                 )
+                if not payload.strip():  # No output from template, ignore
+                    _LOGGER.debug(
+                        "Empty template output for entity: %s with state topic: %s. Payload: '%s', with value template '%s'",
+                        self._config[CONF_NAME],
+                        self._config[CONF_STATE_TOPIC],
+                        msg.payload,
+                        value_template,
+                    )
+                    return
+
             if payload == self._config[CONF_PAYLOAD_ON]:
                 self._state = True
             elif payload == self._config[CONF_PAYLOAD_OFF]:
                 self._state = False
             else:  # Payload is not for this entity
-                _LOGGER.warning(
+                template_info = ""
-                    "No matching payload found for entity: %s with state topic: %s. Payload: %s, with value template %s",
+                if value_template is not None:
+                    template_info = f", template output: '{payload}', with value template '{str(value_template)}'"
+                _LOGGER.info(
+                    "No matching payload found for entity: %s with state topic: %s. Payload: '%s'%s",
                     self._config[CONF_NAME],
                     self._config[CONF_STATE_TOPIC],
-                    payload,
+                    msg.payload,
-                    value_template,
+                    template_info,
                 )
                 return
 

tests/components/mqtt/test_binary_sensor.py

@@ -259,6 +259,76 @@ async def test_setting_sensor_value_via_mqtt_message_and_template(hass, mqtt_moc
     assert state.state == STATE_OFF
 
 
+async def test_setting_sensor_value_via_mqtt_message_and_template2(
+    hass, mqtt_mock, caplog
+):
+    """Test the setting of the value via MQTT."""
+    assert await async_setup_component(
+        hass,
+        binary_sensor.DOMAIN,
+        {
+            binary_sensor.DOMAIN: {
+                "platform": "mqtt",
+                "name": "test",
+                "state_topic": "test-topic",
+                "payload_on": "ON",
+                "payload_off": "OFF",
+                "value_template": "{{value | upper}}",
+            }
+        },
+    )
+    await hass.async_block_till_done()
+
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_OFF
+
+    async_fire_mqtt_message(hass, "test-topic", "on")
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_ON
+
+    async_fire_mqtt_message(hass, "test-topic", "off")
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_OFF
+
+    async_fire_mqtt_message(hass, "test-topic", "illegal")
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_OFF
+    assert "template output: 'ILLEGAL'" in caplog.text
+
+
+async def test_setting_sensor_value_via_mqtt_message_empty_template(
+    hass, mqtt_mock, caplog
+):
+    """Test the setting of the value via MQTT."""
+    assert await async_setup_component(
+        hass,
+        binary_sensor.DOMAIN,
+        {
+            binary_sensor.DOMAIN: {
+                "platform": "mqtt",
+                "name": "test",
+                "state_topic": "test-topic",
+                "payload_on": "ON",
+                "payload_off": "OFF",
+                "value_template": '{%if value == "ABC"%}ON{%endif%}',
+            }
+        },
+    )
+    await hass.async_block_till_done()
+
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_OFF
+
+    async_fire_mqtt_message(hass, "test-topic", "DEF")
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_OFF
+    assert "Empty template output" in caplog.text
+
+    async_fire_mqtt_message(hass, "test-topic", "ABC")
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_ON
+
+
 async def test_valid_device_class(hass, mqtt_mock):
     """Test the setting of a valid sensor class."""
     assert await async_setup_component(