[GitHub] [airflow] eladkal edited a comment on pull request #18471: Improve error message for BranchPythonOperator when no task_id to follow

[GitBox <gi...@apache.org>]

eladkal edited a comment on pull request #18471:
URL: https://github.com/apache/airflow/pull/18471#issuecomment-925980093


   @uranusjr correct me if I'm wrong but this requires rewriting [skip_all_except](https://github.com/apache/airflow/blob/958b679dae6bbd9def7c60191c3a7722ce81382a/airflow/models/skipmixin.py#L134)
   The way I see it I can't just blindly skip all downstream tasks as unlike `ShortCircuitOperator` branching does respect trigger rules so I need to skip all downstream tasks until a join/junction task is found.
   Since my input is None we need to search if such junction exists.
   So I need to set difference between two cases:
   
    If I have a case of:
   
               # branch  ----->  task2
               #   \           
               #    \        
               #       task1
               
   Then I need to execute [skip](https://github.com/apache/airflow/blob/958b679dae6bbd9def7c60191c3a7722ce81382a/airflow/models/skipmixin.py#L66)
   but If I have a case like:
   
               # branch  ----->  task2   <----- task3
               #   \           
               #    \        
               #       task1
              
    Then I need to run `skip_all_except(context['ti'],['task2])` because task2 may still run depends on its `trigger_rule`.
   


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