I'll give a bit of background as it's possible I'm doing something wrong from a fundamental starting point. I have a package called ims.users which has a very simple css file. I can get to it directly at ++resource++ims.users/main.css just fine. In Plone 4 I would make a cssregistry import step to put this on a set - very simple, no problem. In Plone 5 this appears to still be possible and it will put it in the legacy bundle. It works on my local machine but not on my dev server for some reason - the compiled css for plone-legacy is a 0 byte file. With no errors thrown this is going to be a pain to debug.
But I'm not sure this is the best way to register my css anyway. On my local machine I abandoned the cssregistry step and set about trying to make a new bundle and new resource TTW. I created a new resource with name ims-users and CSS/LESS value of "++resource++ims.users/main.css" and it save - it saves but strips out the CSS/LESS value.
At this point I'm just confused and frustrated. Do I want to create a resource and a bundle for each of my packages or should I use plone-legacy? How do I debug a bundle that compiles to an empty file but doesn't throw an error? How do I debug an attempt to add a resource that doesn't save the CSS/LESS value I gave it but doesn't throw an error? This is a lot of complexity and dev time to add padding to an element.
I was originally going to move my comments over to that issue, but on second thought I have some follow up questions more specific to my case.
The way I understood bundles was that you could take a bunch of resources (js and css) and TTW hit build and it would compile it into a single file. Or if you were compiling it yourself with something, you could include a value with key "csscompilation" pointing to the compiled location. In my case and Andreas case we don't actually need to do any compiling or have any LESS files, so we would not create any resources - I would just create a bundle that has a csscompilation value of "++resource++ims.users/main.css".