houqp commented on a change in pull request #8534:
URL: https://github.com/apache/airflow/pull/8534#discussion_r415375821
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File path: airflow/providers/amazon/aws/hooks/base_aws.py
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@@ -62,16 +63,14 @@ class AwsBaseHook(BaseHook):
def __init__(
self,
- aws_conn_id="aws_default",
+ aws_conn_id: Optional[str] = "aws_default",
Review comment:
the wording in the documentation linked by @zhongjiajie is a little bit
misleading, which probably caused confusion between `Optional` type and
optional argument.
`def foo(a: Optional[str] = 'test'):` tells mypy that argument `a` needs to
be either `None` or a `str`. Since the default value `'test` is a string, this
is a valid use of `Optional` type annotation. `a: Optional[str] = None` is also
a valid annotation.
If we allow `a` to take `None` as value, but annotate it as `def foo(a:
str='test')`, then mypy will not be able to catch errors like `b = a +
'_suffix'` because the annotation `str` tells mypy that `a` will always be a
string. Mypy will also prevent users from calling `foo` with `foo(None)` due to
missing `Optional` in the type annotation, which is not what we want.
Behavior wise, both `aws_conn_id: Optional[str] = None` and `aws_conn_id:
Optional[str] = 'aws_default'` will work for aws hook. I kept it to
`aws_conn_id: Optional[str] = 'aws_default'` because that's what it used to be.
I don't know if it's going to break anything if default is changed to `None`
since there might be users out there actually using `aws_default` connection as
the way to inject global aws credential instead of using default credential
chain lookup.
In AWS land, the best practice is to use default credential chain lookup, so
`aws_conn_id: Optional[str] = None` would be better. It's up to us whether we
are willing risk breaking existing users in order to adopt a better practice. I
don't have a strong opinion on this, but if anyone thinks we should take the
chance for airflow 2.0, I am open to change it to `None`.
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