Log entity_id payload and template on MQTT value template error (#98353)

* Log entity_id payload and template on error

* Also handle cases with default values.

* Do not log payload twice

Co-authored-by: Erik Montnemery <erik@montnemery.com>

* Tweak test to assert without payload

* black

---------

Co-authored-by: Erik Montnemery <erik@montnemery.com>

homeassistant/components/mqtt/models.py

@@ -231,11 +231,21 @@ class MqttValueTemplate:
                 values,
                 self._value_template,
             )
-            rendered_payload = (
+            try:
-                self._value_template.async_render_with_possible_json_value(
+                rendered_payload = (
-                    payload, variables=values
+                    self._value_template.async_render_with_possible_json_value(
+                        payload, variables=values
+                    )
                 )
-            )
+            except Exception as ex:  # pylint: disable=broad-except
+                _LOGGER.error(
+                    "%s: %s rendering template for entity '%s', template: '%s'",
+                    type(ex).__name__,
+                    ex,
+                    self._entity.entity_id if self._entity else "n/a",
+                    self._value_template.template,
+                )
+                raise ex
             return rendered_payload
 
         _LOGGER.debug(
@@ -248,9 +258,24 @@ class MqttValueTemplate:
             default,
             self._value_template,
         )
-        rendered_payload = self._value_template.async_render_with_possible_json_value(
+        try:
-            payload, default, variables=values
+            rendered_payload = (
-        )
+                self._value_template.async_render_with_possible_json_value(
+                    payload, default, variables=values
+                )
+            )
+        except Exception as ex:  # pylint: disable=broad-except
+            _LOGGER.error(
+                "%s: %s rendering template for entity '%s', template: "
+                "'%s', default value: %s and payload: %s",
+                type(ex).__name__,
+                ex,
+                self._entity.entity_id if self._entity else "n/a",
+                self._value_template.template,
+                default,
+                payload,
+            )
+            raise ex
         return rendered_payload
 
 

tests/components/mqtt/test_init.py

@@ -41,6 +41,7 @@ from .test_common import help_all_subscribe_calls
 
 from tests.common import (
     MockConfigEntry,
+    MockEntity,
     async_fire_mqtt_message,
     async_fire_time_changed,
     mock_restore_cache,
@@ -417,6 +418,37 @@ async def test_value_template_value(hass: HomeAssistant) -> None:
         assert template_state_calls.call_count == 1
 
 
+async def test_value_template_fails(
+    hass: HomeAssistant, caplog: pytest.LogCaptureFixture
+) -> None:
+    """Test the rendering of MQTT value template fails."""
+
+    # test rendering a value fails
+    entity = MockEntity(entity_id="sensor.test")
+    entity.hass = hass
+    tpl = template.Template("{{ value_json.some_var * 2 }}")
+    val_tpl = mqtt.MqttValueTemplate(tpl, hass=hass, entity=entity)
+    with pytest.raises(TypeError):
+        val_tpl.async_render_with_possible_json_value('{"some_var": null }')
+    await hass.async_block_till_done()
+    assert (
+        "TypeError: unsupported operand type(s) for *: 'NoneType' and 'int' "
+        "rendering template for entity 'sensor.test', "
+        "template: '{{ value_json.some_var * 2 }}'"
+    ) in caplog.text
+    caplog.clear()
+    with pytest.raises(TypeError):
+        val_tpl.async_render_with_possible_json_value(
+            '{"some_var": null }', default=100
+        )
+    assert (
+        "TypeError: unsupported operand type(s) for *: 'NoneType' and 'int' "
+        "rendering template for entity 'sensor.test', "
+        "template: '{{ value_json.some_var * 2 }}', default value: 100 and payload: "
+        '{"some_var": null }'
+    ) in caplog.text
+
+
 async def test_service_call_without_topic_does_not_publish(
     hass: HomeAssistant, mqtt_mock_entry: MqttMockHAClientGenerator
 ) -> None: