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https://issues.apache.org/jira/browse/AIRFLOW-4070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16789809#comment-16789809
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ASF GitHub Bot commented on AIRFLOW-4070:
-----------------------------------------
newtonle commented on pull request #4904: [AIRFLOW-4070] AirflowException ->
log.warning for duplicate task dependencies
URL: https://github.com/apache/airflow/pull/4904
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"
- https://issues.apache.org/jira/browse/AIRFLOW-4070
- In case you are fixing a typo in the documentation you can prepend your
commit with \[AIRFLOW-XXX\], code changes always need a Jira issue.
- In case you are proposing a fundamental code change, you need to create
an Airflow Improvement
Proposal([AIP](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+Improvements+Proposals)).
### Description
- [x] Here are some details about my PR, including screenshots of any UI
changes:
For duplicate task dependencies, I've changed raising an Airflow exception
to a log warning.
### Tests
- [x] My PR adds the following unit tests __OR__ does not need testing for
this extremely good reason:
No tests--just changing the exception to a warning.
### 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/)":
1. Subject is separated from body by a blank line
1. Subject is limited to 50 characters (not including Jira issue reference)
1. Subject does not end with a period
1. Subject uses the imperative mood ("add", not "adding")
1. Body wraps at 72 characters
1. Body explains "what" and "why", not "how"
### Documentation
- [ ] In case of new functionality, my PR adds documentation that describes
how to use it.
- When adding new operators/hooks/sensors, the autoclass documentation
generation needs to be added.
- 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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> AirflowException on repeated dependencies prevents automated dependencies
> -------------------------------------------------------------------------
>
> Key: AIRFLOW-4070
> URL: https://issues.apache.org/jira/browse/AIRFLOW-4070
> Project: Apache Airflow
> Issue Type: Bug
> Reporter: Newton Le
> Assignee: Newton Le
> Priority: Major
>
> We are trying to build automated dependencies based on data. For example, if
> Task A requires data from Task B, then a task dependency will be
> automatically generated. At the same time, we still want to allow users to
> specify explicit dependencies, e.g. `task_a >> task_b`.
> Airflow's current way of raising an exception on duplicate dependencies
> currently blocks this implementation. Also, I can't think of a good
> justification for it. For the purposes I can imagine, logging a warning seems
> more than sufficient.
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