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Fix Flask 2.0 Warnings in Flask-Login, Flask-WTF & Flask-Debugtoolbar


In this video we'll go over 3 pull requests that fix a few deprecation warnings in 3 popular Flask extensions.

Quick Jump: Going Over Everything

I recently updated an app to use Flask 2.0 and all 3 of those libraries started to throw deprecation warnings. I decided to contribute back to those projects and fix them in a few pull requests. This video goes over creating those PRs.

The takeaway here is don’t be afraid to contribute code to an unfamiliar code base. I never looked at the source code of these projects prior to adding these PRs.

Going Over Everything


  • 0:13 – Flask 2.0 recently came out
  • 0:50 – Let’s be proactive and make PRs on libraries we use
  • 3:39 – Reading a deprecation warning
  • 4:46 – If you’re going to open an issue, consider a PR instead
  • 5:49 – Addressing the warning for Flask-Login
  • 7:39 – Addressing the warning for Flask-WTF
  • 9:53 – Tracking down an issue for a less helpful deprecation warning
  • 13:19 – Addressing the warning for Flask-Debugtoolbar
  • 15:42 – Popping open a Python interpreter to test the core of our patch
  • 17:51 – If you want to make an open source maintainer’s day, open a PR

What was the last PR you added to an open source project? Let me know below.

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