We usually separate modules based on their domain, e.g. one for all basic templates, one for the theme, one for the newsletter, one for providing an API to access some third-party-system and so on. Therefore resources may be located in more than a single resources directory.

I wondered why Magnolia just allows to specify a single magnolia.resources.dir as it's very interruptive to switch the directory whenever I change a module that contains templates. That's why I implemented a ResourceOrigin provider to allow multiple resource directories. The code is appended. Hopefully the code or the idea is of some use.

btw, it's a hell to write tests for this as long as all the default ResourceOrigin implementations are final.