Reinstate region to default_args for Alibaba example DAGs

[josh-fell]

Related: #19891

In a previous PR to fix Mypy errors, the region arg was removed from default_args in the Alibaba example DAGs. While this did alleviate Mypy errors it removed a valid DAG-authoring feature that was being showcased. This PR returns the region arg to default_args as well as handling Mypy errors.

Note: Generally it seems like the first approach to handle these call-arg errors from Mypy related to default_args functionality is to add the ignore comments where appropriate. A proper fix for these scenarios seems very non-trivial and this is a good interim solution.

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[potiuk]

Should we make region Optional and raise Runtime Error instead as I did in #20422 ?

[potiuk]

See: https://github.com/apache/airflow/pull/20422/files#diff-aec3e30af161525a7290fd9f420169f8a107c929e9b33b613bef4c03dd228c2dR70

[potiuk]

Ah nice. Using stub files seems to be a better solution. I will use that in #20422 too

[josh-fell]

Hmm. It seems that the Mypy checks in CI and running mypy --namespace-packages airflow/providers/alibaba/cloud locally in a Breeze container have different results. Still showing a call-arg error for region even with the stubs.

[potiuk]

Hmm. It seems that the Mypy checks in CI and running mypy locally in Breeze have different results. Still showing a call-arg error for region even with the stubs.

Not for me #20422 It worked just fine in Breeze - same way as in CI.

It could be about .pyc files probably ? (wild guess) Did you actually use breeze or mypy in local virtualenv? And maybe you had some locally generated .pyc files ? Because in Breeze. PYTHONDONTWRITEBYTECODE=true is set, so .pyc files are not generated, but if you run it locally they coudl be

[potiuk]

Ah noe

Suggested change

	region: str = ...,
	region: Optional[str] = None

[potiuk]

And others.

[josh-fell]

Oh OK. Let me try this!

[potiuk]

Hmm. It seems that the Mypy checks in CI and running mypy --namespace-packages airflow/providers/alibaba/cloud locally in a Breeze container have different results. Still showing a call-arg error for region even with the stubs.

One more comment - what worked for me, I set the fields to be "Optional[str] = None" in stubs. That was what worked perfectly for me.

[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.

[josh-fell]

There was a typo in an import within the stub file which was causing the stub to not be recognized. @potiuk can you review again when you get a chance please?