The bug
MC-121379 happens again, with errors such as
Non [a-z0-9/._-] character in path of location: namespace:worldgen/structure/.DS_Store
How to reproduce
1. Start the game with the output log enabled
2. Load a data pack that has .DS_Store files (which are common on macOS)
3. Notice the errors in the log
Expected behavior
I expected the game to exclude these hidden system files when loading data packs and resource packs, and I expected this wouldn't show errors in the log.
We decided to fix it by ignoring files that don't match this pattern, but still reporting this in logs - having unrecognized files in packs is unsupported.