Why should the image URLs be resolvable without naming the resource inside the URL?
What is the meaning of the ++plone++production and ++unique++ namespaces? Where are they coming from? When and why were they introduced?
I believe the ++plone++production and ++unique++ urls were introduced so you could have highly cached resources. I forget the reason why but appending unique urls with a query string wasn't enough for some people to do cache busting urls.
FWIU it's a namespace to allow caching for items in your ZMI's portal_resources. On site creation, Plone builds an aggregate of all bundles in order to reduce the number of resources in (resource registry's) production mode. That's part of what you see in the URL.
Problem is AFAIK you shouldn't have two ++namespaces++ in any URL so if you're manually adding the ++resource++ reference in your CSS/JS files, you should probably drop it.
Browser resource directory worked as expected until 5.0.4. Now in 5.0.5 there is something horribly broken.
I am not using plone.resource in an explicit way. I am using browser resources as we used it for years and as configured for years....so this is a behavioral change a bug or a feature or a regression?
Further investigations: the problem with the broken resource URLs disappears when I enable the dev mode for resource registries and starting the development mode for CSS for the plone-legacy bundle and saving afterwards...then the icons are loaded properly...disabling the dev mode again makes the problem reappear..so again we have to blame the resource registries?
" the way you're doing it "...how else would you do it? There is nothing different from the way we did it in Plone 4.X. How else other than using url(..) with a relative URL would you reference resources from a configured resource directory?
Well, why was this working in all Plone 5.0.X releases so far? Why is it broken with 5.0.5?
I am under the impression that the resource registry implementation is in duct-tape mode...fixing bug and edge-cases here and there without having the big picture and having an idea about constraints and implications...since nine months there is no working resource registry implementation available that would be working for the most basic usecase (in this case using my own JS and CSS file).
My suggestion is to remove the Plone legacy bundle completely as soon as possible (best for Plone 5.1).
It is broken.
It does not work.
It is obviously impossible to fix outstanding issues.
Nobody has the full picture for understanding the problem and fixing the outstanding issues (and there is always one issue more).