[jira] [Created] (AIRFLOW-883) Assigning operator to DAG via bitwise composition does not pickup default args

[Daniel Huang (JIRA)]

Daniel Huang created AIRFLOW-883:
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             Summary: Assigning operator to DAG via bitwise composition does 
not pickup default args
                 Key: AIRFLOW-883
                 URL: https://issues.apache.org/jira/browse/AIRFLOW-883
             Project: Apache Airflow
          Issue Type: Bug
          Components: models
            Reporter: Daniel Huang
            Priority: Minor


This is only the case when the operator does not specify {{dag=dag}} and is not 
initialized within a DAG's context manager (due to 
https://github.com/apache/incubator-airflow/blob/fb0c5775cda4f84c07d8d5c0e6277fc387c172e6/airflow/utils/decorators.py#L50)

Example:

{code}
default_args = {
    'owner': 'airflow', 
    'start_date': datetime(2017, 2, 1)
}
dag = DAG('my_dag', default_args=default_args)
dummy = DummyOperator(task_id='dummy')

dag >> dummy
{code}

This will raise a {{Task is missing the start_date parameter}}. I _think_ this 
should probably be allowed because I assume the purpose of supporting {{dag >> 
op}} was to allow delayed assignment of an operator to a DAG. 

I believe to fix this, on assignment, we would need to go back and go through 
dag.default_args to see if any of those attrs weren't explicitly set on 
task...not the cleanest. 



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