[GitHub] [airflow] uranusjr commented on issue #27081: Wrong missing args error when initialising operator with multiple inheritance

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

uranusjr commented on issue #27081:
URL: https://github.com/apache/airflow/issues/27081#issuecomment-1280243692

   > work as expected in Python.
   
   How? I removed `BaseOperator` from the given example:
   
   ```python
   class R:
       def __init__(**kwargs):
           pass
   
   class A(R):
       def __init__(self, *, value: str, **kwargs):
           super().__init__(**kwargs)
   
   class B(R):
       def __init__(self, *, value: str, **kwargs):
           super().__init__(**kwargs)
   
   class C(A, B):
       def __init__(self, *, value: str, **kwargs):
           super().__init__(value=value, **kwargs)
   
   C(task_id="test", value="value")
   ```
   
   And it still fails.
   
   ```
   Traceback (most recent call last):
     File "<stdin>", line 24, in <module>
       C(task_id="test", value="value")
     File "<stdin>", line 21, in __init__
       super().__init__(value=value, **kwargs)
     File "<stdin>", line 11, in __init__
       super().__init__(**kwargs)
   TypeError: __init__() missing 1 required keyword-only argument: 'value'
   ```
   
   Python’s `super` chain follows MRO (C→B→A→BaseOperator in this example), so the `super().__init__` calls in `C.__init__` calls `B.__init__`, **and the `super().__init__` in `B.__init__` calls `A.__init__`**, which is missing the required `value` argument.
   
   From what I can tell, `apply_defaults` is doing its job properly. It obscures the traceback, which we could improve, but the error is legistimate.


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