Fixing an 'unknown source' issue preventing Eclipse debugging within a custom Processing library

I’m building myself a processing library, and I would like to be able to step into my library methods fro my Proclipsing sketch in order to properly debug. However, after trying numerous fixes, I am unable to get this functionality.

I am using the Processing library template, and its built-in .xml + ant to compile my .jar

Everything runs well, but if I attempt to step into a library method I end up on this screen. I have tried attaching the source, but that does not seem to change anything.

I have also tried all the suggestions on this page to no avail.

This is how my source is attached to the .jar