Django 4.0 compatibility issue: Node.render should return a string

[thibaudcolas]

Issue Summary

cc @nickmoreton who fixed our test data in #165. Our test suite was failing in Django 4.0 because the new version of Django assumes the output of Node.render is a string. The error we got in our test suites was from Django’s templates rendering:

sequence item 4: expected str instance, NoneType found

This was a misc. performance improvement – from the release notes:

NodeList.render() no longer casts the output of render() method for individual nodes to a string. Node.render() should always return a string as documented.

Corresponding PR: django/django#14503, and blame of those three lines.

Steps to Reproduce

Use this library and override a tag by providing raw data, with a value other than a string as the tag output.

Potential fixes

One option would be for us to re-introduce this casting for backwards compatibility. I believe it’s only needed here:

django-pattern-library/pattern_library/monkey_utils.py

Line 78 in dffd369

return result

Another option would be to keep our implementation as-is and document the issue so people upgrading to Django 4.0 are aware they’ll need to change their raw definitions to be strings. We’d also want to remove/change the test cases updated in #165, as right now they aren’t testing much. We could also consider adding an assert for this in our code / check the type and throw a custom exception. Not too sure if worthwhile or not.

[thibaudcolas]

@zerolab @bcdickinson when you have a chance I could use your input on this. Would be great for us to agree on a fix before lots of our projects start upgrading to Django 4.0.

[zerolab]

My gut feeling is that we should handle this ourselves since we're kind of acting (in a veeery loose sense of the concept) like a fancy NodeList with individual bits patched.

Also, will save updating hundreds of yaml files