[jira] [Commented] (AIRFLOW-6170) BranchPythonOperator does not do XCom push of returned value

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AIRFLOW-6170?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16987692#comment-16987692 ] 

ASF GitHub Bot commented on AIRFLOW-6170:
-----------------------------------------

baolsen commented on pull request #6726: [AIRFLOW-6170] BranchPythonOperator does not do XCom push of returned value
URL: https://github.com/apache/airflow/pull/6726
 
 
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   ### Description
   
   - [X] Here are some details about my PR, including screenshots of any UI changes:
   Added return_value from BranchPythonOperator along with appropriate test.
   ### Tests
   
   - [X] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason:
   Added a test for XCom push/pull of return_value from BranchPythonOperator
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> BranchPythonOperator does not do XCom push of returned value
> ------------------------------------------------------------
>
>                 Key: AIRFLOW-6170
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-6170
>             Project: Apache Airflow
>          Issue Type: Bug
>          Components: operators
>    Affects Versions: 1.10.6
>            Reporter: Bjorn Olsen
>            Assignee: Bjorn Olsen
>            Priority: Minor
>
> BranchPythonOperator subclasses PythonOperator, and after it has selected a branch we get a message like this in the task log:
> [2019-12-04 08:39:59,960] \{python_operator.py:114} INFO - Done. Returned value was: <chosen_task>
>  This returned value is from the execute() method.
> A user would expect the returned value from this to be pushed to an XCOM; but this does not happen due to no return value from the BranchPythonOperator's execute method.
>   
> {code:java}
>      def execute(self, context: Dict):
>          branch = super().execute(context)
>          self.skip_all_except(context['ti'], branch)
>  {code}
>  
> If we do an XCOM push of the result then we can use the decision made by BranchPythonOperator in downstream tasks.
> Eg consider this dependency chain:
>  get >> branch >>   [ create, update ]>> join >> execute
> The 'execute' task might need to know whether the 'branch' decided to create a new thing to run, or whether to use the existing one from the 'get'. Without an XCOM push from the branch return value, it is difficult to pick up the correct value later on.



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