Change 501820 had a related patch set uploaded (by Jack Phoenix; owner: Jack Phoenix):
[mediawiki/extensions/Interwiki@master] Global interlanguage links feature

https://gerrit.wikimedia.org/r/501820

How would this handle the various cases where one local wiki wants to handle an interwiki prefix in some different or non-standard way, for instance to point wikipedia: to the local-language Wikipedia instead of the American-language version? How would it handle the case where each local project wants to decide which fork of the same wiki to link to?

At the moment, *.uncyclopedia.info has [[mw:Extension:Interwiki]] operating independently on each wiki, allowing sysops on each local project free rein to change anything.

There have been instances where there have been two projects in the same language. Some are communities which have been split in two (mostly due to Wikia's infamous pattern of keeping old projects open after a dissatisfied community has forked and gone elsewhere); every other language community in the project - if they have access - ends up having to decide who to link to. Some are unrelated wikis on the same theme in the same style in the same language. For instance, there may be two or three unrelated German-language projects wanting access to that precious "in other language" sidebar, so one might be assigned bar: (for Bavarian).

There have even been cases where two Uncyclopedia languages just plain refuse to link to each other (I think pt: to gl:/mwl: was one instance); sometimes some minor language will just become an otherwise-quiet refuge for users who have been blocked or banned from the larger project (much like en.wikipedia users in exile occasionally turn up on simple.wikipedia) and, in the worst cases, the two projects will refuse to link to each other.

In other words, uncyclopedia.info is the sort of place where interwikidata.py script writers are sent in the next life if they've committed some unspeakable evil in this world for which the deity of their choice refuses to forgive. An eternal and unequalled torment. :)

It would be useful to have a set of global defaults for a wiki family and then allow a local override to deal with these few weird edge cases which can't be handled by sane and consistent means. Would the proposed extension be able to do this?

This only affects interlanguages, thus the different language versions of the same project. As for issues with duplicate projects of the same language, well... we need to resolve that, frankly. Having different other languages randomly link to one or the other just gets confusing, and doesn't help resolve the actual problem, namely that we are limited communities of limited capacity across any and all languages we do support, and we need to be bringing them together, not promoting splintering further.

I get that actually sorting that out will require folks, well, talking to each other and sorting it out, but that's a social problem that would not be aided any by being repeated across each language.

The global interwikis otherwise will continue to be overridable locally.

OK, thanks. I've tested this by setting $wgInterwikiCentralInterlanguageDB = 'uncyc_commons'; on one of the inactive projects (which would benefit from your shared table, as there's no one local to update/maintain the data) but not setting $wgInterwikiCentralInterlanguageDB on whichever active projects wanted to retain independent local control. Your solution appears to make sense.

Change 501820 merged by jenkins-bot:
[mediawiki/extensions/Interwiki@master] Global interlanguage links feature

https://gerrit.wikimedia.org/r/501820