🇺🇸United States @becw

And, here's an updated patch where I filled out the rest of the tests.

I needed the work in this ticket, but the patch against 1.3.x no longer applies, and I didn't see a recent update in the issue fork on GitLab, so I did a bit of refactoring and have a working approach.

I've added a PHPUnit kernel test, but there's some things where I'm not exactly sure what the existing behavior is, so I need to validate that before finishing those tests. Anyway, here's my WIP.

Fixed as part of #3401877.

Thanks!