In this change https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/498348, we ended up changing signature of cache-aware services to accept WANObjectCache instead of BagOfStuff.
BagOfStuff is our interface that implements PSR-6 Cache Interfaces. With this change, we narrowed down the dependency of those services to a certain provider that neither implements BagOfStuff nor implements PSR-6.
There was a reason to accept this change temporarily to solve some performance-related issue that we faced on Wikidata, though that change is not the most appropriate for wider-range of Wikibase users.
related comment on the patch
We want cache-aware services in Wikibase to depend again on either BagOfStuff or PSR-6 interfaces. To do that without interrupting Wikidata's need for using the functionality of WANObjectCache, we will have to:
- find a way to make WANObjectCache implement PSR-6 or BagOfStuff
- allow configuring which implementation is used easily per wikibase instance, if that's not the case already.