BaseBranchOperator should push to xcom by default

[HaloKo4]

Apache Airflow version: 2.0.0

Kubernetes version (if you are using kubernetes) (use kubectl version):
Not relevant

Environment:
Not relevant

What happened:

BranchPythonOperator performs xcom push by default since this is the behavior of PythonOperator.
However BaseBranchOperator doesn't do xcom push.

Note: It's impossible to push to xcom manually because the BaseBranchOperator has no return in it's execute method. So even when using do_xcom_push=True it won't help
https://github.com/apache/airflow/blob/master/airflow/operators/branch.py#L52

What you expected to happen:
BaseBranchOperator to do xcom push of the branch it choose to follow as the default or at least to support the parameter of do_xcom_push=True

[turbaszek]

It's impossible to push to xcom manually

Strictly speaking it is possible because you can override the execute method in your custom branch operator.

Apart from that your suggestion make sense to me - I don't see any drawbacks to that. Would you mind opening a PR?

[ashmeet13]

Hi!
I would like to pick this issue up if it's open and not being worked upon.

From what I understand the execute function in BaseBranchOperator does not return the value calculated by choose_branch.

A simple change from -

    def execute(self, context: Dict):
        self.skip_all_except(context['ti'], self.choose_branch(context))

to

    def execute(self, context: Dict):
        branches_to_execute = self.choose_branch(context)
        self.skip_all_except(context['ti'], branches_to_execute)
        return branches_to_execute

should do the trick and do_xcom_push=True should be usable
New to Airflow so please do correct me if I am wrong!

Thank you.