mingshi-wang commented on pull request #20547:
URL: https://github.com/apache/airflow/pull/20547#issuecomment-1002760879
> It's still not really backwards compatible (in the sense a having a New
Sensor returnig PokeReturnValue run on airlfow pre 2.3).
>
> If you return PokeReturnValue() in Airlfow 2.2. it will not work. The
BaseSensorOperator from Airflow 2.2 will run this:
>
> ```
> while not self.poke():
> ```
>
> And it will always finish after first check no matter what "is_done" is.
In this case self.poke() returns PokeReturnValue() class which is Truthy no
matter what is set in `is_done`).
>
> But It could be made backwards compatible - and I like this much more than
my "return Truthy" approach.
>
> Should be enough to do this:
>
> ```
> class PokeReturnValue:
> """
> Sensors can optionally return this an instance of this class in the
poke method.
> If an xcom value is supplied when sensor is done, then the XCom value
will be
> push through the operator return value.
> """
>
> def __init__(self, is_done, xcom_value=None):
> self.xcom_value = xcom_value
> self.is_done = is_done
>
>
> def __bool__(self):
> return self.is_done
> ```
>
> ~I think this is the BEST approach.~
>
> UPDATE: Nope. It won't work, because in Airflow 2.2 there wil be no
PokeReturnValue class.
> It's still not really backwards compatible (in the sense a having a New
Sensor returnig PokeReturnValue run on airlfow pre 2.3).
>
> If you return PokeReturnValue() in Airlfow 2.2. it will not work. The
BaseSensorOperator from Airflow 2.2 will run this:
>
> ```
> while not self.poke():
> ```
>
> And it will always finish after first check no matter what "is_done" is.
In this case self.poke() returns PokeReturnValue() class which is Truthy no
matter what is set in `is_done`).
>
> But It could be made backwards compatible - and I like this much more than
my "return Truthy" approach.
>
> Should be enough to do this:
>
> ```
> class PokeReturnValue:
> """
> Sensors can optionally return this an instance of this class in the
poke method.
> If an xcom value is supplied when sensor is done, then the XCom value
will be
> push through the operator return value.
> """
>
> def __init__(self, is_done, xcom_value=None):
> self.xcom_value = xcom_value
> self.is_done = is_done
>
>
> def __bool__(self):
> return self.is_done
> ```
>
> ~I think this is the BEST approach.~
>
> UPDATE: Nope. It won't work, because in Airflow 2.2 there wil be no
PokeReturnValue class.
A not-so-ideal way is to declare a dynamic return type:
def poke(self, context: Context) -> Union[bool, 'PokeReturnValue']:
...
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