Using .output on non-templated fields

### Discussed in https://github.com/apache/airflow/discussions/26938 <div type='discussions-op-text'> ^{Originally posted by **stephenonethree** October 7, 2022} I just discovered the `.output` property functionality that apparently was released in Airflow 2 for classic operators, as a simple way of accessing their output XComs. I think that this is a super useful feature because it would allow simpler connections between tasks than what I have been doing until now. Until now, I've been explicitly giving a downstream task the task_ids and XCom names that it needs to pull from its upstreams (as hardcoded string parameters). Something like: ``` # pushes XCom named myvar upstream_task=SomeOperator(task_id='upstream_task') # this is a custom operator and within execute() I have a line roughly like: # actual_input = context['task_instance'].xcom_pull( # dag_id=context['dag'].dag_id, task_ids=upstream_task_id, key=upstream_xcom_name) this_task = OtherOperator( task_id='this_task', upstream_task_id='upstream_task', upstream_xcom_name='myvar' ) upstream_task >> this_task ``` With `.output` I could simplify this to: ``` # pushes XCom named myvar upstream_task=SomeOperator(task_id='upstream_task') this_task = OtherOperator( task_id='this_task', actual_input=upstream_task.output['myvar'] ) upstream_task >> this_task ``` Unfortunately it seems that there is one limitation. On the TaskFlow documentation page (https://airflow.apache.org/docs/apache-airflow/2.4.1/tutorial/taskflow.html#consuming-xcoms-between-decorated-and-traditional-tasks) it says: _Using the .output property as an input to another task is supported only for operator parameters listed as a template_field._ I don't use Jinja templating for very many of my parameters as it's mostly irrelevant for me. So my questions are, is there a technical reason for this limitation? If not, is this limitation something that you are considering dropping in a future Airflow version? I suppose I c…