[GitHub] [airflow] jml opened a new pull request #5757: [AIRFLOW-5100] Use safe_mode configuration setting by default

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

jml opened a new pull request #5757: [AIRFLOW-5100] Use safe_mode configuration setting by default
URL: https://github.com/apache/airflow/pull/5757
 
 
   The scheduler calls `list_py_file_paths` to find DAGs to schedule. It does so
   without passing any parameters other than the directory. This means that
   it *won't* discover DAGs that are missing the words "airflow" and "DAG" even
   if DAG_DISCOVERY_SAFE_MODE is disabled.
   
   Since `list_py_file_paths` will refer to the configuration if
   `include_examples` is not provided, it makes sense to have the same behaviour
   for `safe_mode`.
   
   Make sure you have checked _all_ steps below.
   
   ### Jira
   
   - [x] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR"
   
   ### Description
   
   See above. There are no UI changes.
   
   ### Tests
   
   I stared at the code a long time and couldn't figure out a good place to test.
   
   - `list_py_file_paths` doesn't have direct tests
     - adding a test for this particular branch might be OK, but feels a bit like a [change detector test](https://testing.googleblog.com/2015/01/testing-on-toilet-change-detector-tests.html)
     - If you can point me to a context manager to temporarily override a configuration setting, I could probably write some direct tests that use `tests/dags/` as the source of DAGs
   - `SchedulerJob` is actually exhibiting the bug, and is where the behaviour needs to be correct
     - There's no obvious API to exercise that would let me test this
     - I could theoretically extract a `_make_processor_agent` from `_execute`, and assert things about its return value, but I don't want spend time on that without a core contributor approving it first
     - I would still need a context manager to temporarily override configuration settings 
   
   ### Commits
   
   - [x] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)"
   
   ### Documentation
   
   - [x] In case of new functionality, my PR adds documentation that describes how to use it.
     - All the public functions and the classes in the PR contain docstrings that explain what it does
     - If you implement backwards incompatible changes, please leave a note in the [Updating.md](https://github.com/apache/airflow/blob/master/UPDATING.md) so we can assign it to a appropriate release
   
   ### Code Quality
   
   - [x] Passes `flake8`
   

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