uranusjr edited a comment on issue #8171:
URL: https://github.com/apache/airflow/issues/8171#issuecomment-806169069
I wonder if type checks can be used to catch these kinds of issues. There
are a lot of `current_app.dag_bag`, `current_app.appbuilder`, etc., which are
not covered by Mypy due to the dynamic nature of `flask.current_app` (basically
any attributes on it is `Any`). Since we “know” what attributes to expect on
the `current_app` instance within Airflow, maybe we can introduce a typing shim
around it? Something like
```python
# airflow/www/app.py
if TYPE_CHECKING:
from airflow.models.dagbag import DagBag
from airflow.www.security import AirflowSecurityManager
class _AirflowAppBuilder(Protocol):
sm: AirflowSecurityManager
...
class _CurrentApp(Protocol):
dag_bag: DagBag
appbuilder: _AirflowAppBuilder
...
from flask import current_app as _current_app
current_app = cast("_CurrentApp", _current_app)
```
And then all code can import this instead of directly from Flask to be type
checked.
We can alternatively supply a [type
stub](https://mypy.readthedocs.io/en/stable/stubs.html#creating-a-stub)
`flask.pyi` to “lie to” Mypy what type `flask.current_app` is `_CurrentApp`.
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