[GitHub] [airflow] potiuk edited a comment on issue #19884: Type hinted `@task` decorated functions to create typed XComs

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

potiuk edited a comment on issue #19884:
URL: https://github.com/apache/airflow/issues/19884#issuecomment-982728834


   I am with @uranusjr on that one. I think there are a number of cases that we did not realise it might cause if we validate XCom structure at runtime. Python value is that while simple thing are nice, you can (if you want) tap into the power of metaclasses, dynamic attributes and the likes and even if we add runtime warnings, we are limiting ourselves to just the "obvious" cases. I can very easily imagine a case where an implementation of Operator would push to Xcom an object with different internal structure but dynamic get_atrs() that would make it works with specific structure. This is not verifiable at runtime almost by definition.
   
   However I think validating cross-operator xcoms type hints in such situation is possible (for example with PEP 484 and stub files). And since DAGs are Python, we should be able to simply (when we implement it) run mypy on the DAGs and there type hints should help DAG writer to develop the DAG.


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