[AIRFLOW-4490] DagRun.conf should return empty dictionary by default

[dstandish]

Currently, we can access dag_run.conf in templates like so:

 "{{ dag_run.conf.get('abc', 'def_val') }}"

But if no conf is passed to the dag run, the above jinja template will fail upon rendering, because conf will be None.

So currently, to be safe, you have to do this:

 "{{ dag_run.conf and dag_run.conf.get('abc', 'def_val') }}"

This PR changes DagRun model so that it returns an empty dictionary when there is no conf.

Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-XXX
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  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.

Description

• Here are some details about my PR, including screenshots of any UI changes:

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• 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":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
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Code Quality

• Passes flake8

[codecov-io]

Codecov Report

Merging #5388 into master will decrease coverage by 0.28%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #5388      +/-   ##
==========================================
- Coverage    84.7%   84.41%   -0.29%     
==========================================
  Files         679      679              
  Lines       38488    38494       +6     
==========================================
- Hits        32600    32496     -104     
- Misses       5888     5998     +110

Impacted Files	Coverage Δ
airflow/models/dagrun.py	96.68% <100%> (+0.09%)	⬆️
airflow/kubernetes/volume_mount.py	44.44% <0%> (-55.56%)	⬇️
airflow/kubernetes/volume.py	52.94% <0%> (-47.06%)	⬇️
airflow/kubernetes/pod_launcher.py	45.25% <0%> (-46.72%)	⬇️
airflow/kubernetes/refresh_config.py	50.98% <0%> (-23.53%)	⬇️
...rflow/contrib/operators/kubernetes_pod_operator.py	78.75% <0%> (-20%)	⬇️

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[dstandish]

I got rid of the change to template context, which initially provided an empty DagRun() object if no dag run. Accordingly this PR no longer touches skip mixin.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[OmerJog]

@dstandish can you rebase?

[dstandish]

@OmerJog I just resolved conflicts using github's "resolve conflicts" thing -- i will rebase and squash later this week.

What do you think is the better approach? This or #5387?

#5387 adds a "dag_run_conf" to context. The nice thing about that approach is then it doesn't fail when there is no dag_run (i.e. when you are just testing template rendering in interactive console).

If you still think this is valuable I can mention it in #development slack chat -- I don't really use dag run conf anymore so I lost interest.

[dstandish]

@OmerJog also you are welcome to take this over and do the rebase and do the squeaky-wheeling if you want :)

[OmerJog]

@dstandish tests did not run because of Falke8 error:
tests/models/test_taskinstance.py:1285:1: W293 blank line contains whitespace

can you resolve this?

[dstandish]

@dstandish tests did not run because of Falke8 error:
tests/models/test_taskinstance.py:1285:1: W293 blank line contains whitespace

can you resolve this?

@OmerJog rebased. passed flake8 locally.

[OmerJog]

@ashb ping :)

[tooptoop4]

stale block

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.