[AIRFLOW-5039] Fix broken XCom JSON serialization

[roo-oliv]

Make sure you have checked all steps below.

https://issues.apache.org/jira/browse/AIRFLOW-5039

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
  • 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).
  • 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
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• 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 so we can assign it to a appropriate release

[ashb]

⁉️

[roo-oliv]

Sorry for that @ashb, this PR is in draft because I'm yet to add unit tests.

[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.

[rifqifatih]

Hi @allrod5, I'm trying to overcome a similar issue and noticed that this PR is not yet merged. Is there anything left to be done beside the unit test?

Edit: might be able to help on unit test if needed.

[roo-oliv]

Hi @rifqifatih, I've come to realize that the issue was not with Airflow itself but that my project was relying on Airflow saving and loading datetimes objects directly without my code having to serialize and deserialize these datetimes.

So I'm unsure if this is a behaviour Airflow wants to keep (doesn't seem that logical to have this datetime parsing enabled by default at least).