This should not be a blocking issue if we disregard T206426: Storing multiple sitelinks to a multilingual wiki which I do not think we should consider implementing except for possibly allowing sitelinks to be prefixed (a la Special:MyLanguage/) on their way to their target wiki. See my comment on that task.

As such, I believe we should handle mul.ws as a oldwikisource multilingual wiki in the same fashion we handle other multilingual wikis like: meta, mediawiki, commons, species, wikimania, wikidata, etc.

If we want to renamed oldwikisource across the board (leaving some backwards compatibility for old interwiki links), that is probably a good idea too. I recommend mulwikisource. However, that should not block editors from manipulating Wikidata sitelinks for this wiki (as per Jarekt's earlier comment, apparently 11 Wikidata items already have such sitelinks but they do not display properly on Wikidata entity pages and normal editors cannot otherwise manipulate them).

If we do this and handle this wiki the same as other multilingual wikis this has some implications:

• this wiki will likely show up on Wikidata entity pages under "Other sites" and not "Wikisource" (we could change the label to "Wikisource monolingual" or similar)
• if we are on a non-wikisource monolingual site (like English Wikipedia), we need to consider how toolbar interwiki links should show when we have multiple wikisource links: one to multilingual Wikisource and one to monolingual Wikisource in the current language (e.g., English Wikisource).
• if we are on a monolingual Wikisource site the (e.g., English Wikisource), the toolbar interwiki links should show both other sister projects links in the current language (e.g., English Wikipedia) as well as the multilingual wiki links such as multilingual Wikisource.
• if we are on a multilingual wiki site how should the toolbar interwiki links look when there is a sitelink to multilingual Wikisource and a monolingual Wikisource in the same language as the current wiki. Potentially two Wikisource links need to be considered. I recommend we specify multilingual Wikisource and then just Wikisource as we currently are doing.

For the most part this is how standalone multilingual wikis are already handled so the number of cases that needs consideration and possible changes should be minimal.

In T138332#2397387, @Mbch331 wrote:

This is a know issue and is handled in T54971. Problem is that https://wikisource.org is a multilingual version of Wikisource and can't be handled easily in the current code. See also https://www.wikidata.org/wiki/Wikidata:Wikisource/Development. I think @Lydia_Pintscher could tell more about this.

This has been open for 4 years.

It was possible to add multilingual projects like Commons, Wikispecies and MediaWiki.org. But Wikisource is somehow impossible?

More and more tools build on Wikidata, for example FileImporter (Move-Files-To-Commons) finds the {{NowCommons}} template based on its sitelink in Q5611625, so it can’t offer automatic {{NowCommons}} addition when moving files from oldwikisource. I really hope this will be fixed in the near future.

Sorry folks for dropping the ball on this.
After chatting with @Ladsgroup and reading @Uzume's comment above we can now easily add it to the "other sites" group in the UI. Would that be ok for people? (Making it show up in the Wikisource group is apparently a major major undertaking that I don't think we can justify.)

@Ankry @Zyephyrus @Mahagaja @-jkb- care to make comment for your community? To me it is imperfect though better than not having a link. My biggest concern is that it won't be obvious to users to where to add mulWS links.

In T138332#6631714, @Lydia_Pintscher wrote:

Sorry folks for dropping the ball on this.
After chatting with @Ladsgroup and reading @Uzume's comment above we can now easily add it to the "other sites" group in the UI. Would that be ok for people? (Making it show up in the Wikisource group is apparently a major major undertaking that I don't think we can justify.)

I suggested the same, so I think that would be good.

In T138332#6633418, @Billinghurst wrote:

@Ankry @Zyephyrus @Mahagaja @-jkb- care to make comment for your community? To me it is imperfect though better than not having a link. My biggest concern is that it won't be obvious to users to where to add mulWS links.

I don't think this would be a major issue. Page creators, page importers, Wikidata veterans and bots will pick up on this fast enough. I'd suspect that's the majority that adds links.

Also we can add an item about this to Tech News if it really happens. (possibly twice: once to announce a future change and again when it's done)

Ok let's go for this then.

In T138332#6733731, @Lydia_Pintscher wrote:

Ok let's go for this then.

I'd like that.

In T138332#6633418, @Billinghurst wrote:

@Ankry @Zyephyrus @Mahagaja @-jkb- care to make comment for your community? To me it is imperfect though better than not having a link. My biggest concern is that it won't be obvious to users to where to add mulWS links.

I was going to suggest something, but it has already been done: the section "Other sites" has been renamed to "Multilingual sites". Much better.

Change 655428 had a related patch set uploaded (by Ladsgroup; owner: Ladsgroup):
[operations/mediawiki-config@master] Add sources to specialSiteLinkGroups Wikibase setting

https://gerrit.wikimedia.org/r/655428

Do you know when this will be in production? (Asking for Tech News purposes.)

In T138332#6736215, @Johan wrote:

Do you know when this will be in production? (Asking for Tech News purposes.)

@Lydia_Pintscher When does this work for you?

In T138332#6782916, @Ladsgroup wrote:

In T138332#6736215, @Johan wrote:

Do you know when this will be in production? (Asking for Tech News purposes.)

@Lydia_Pintscher When does this work for you?

Can go anytime from my side. How about Tuesday next week?

Sure.

Change 660664 had a related patch set uploaded (by Ladsgroup; owner: Ladsgroup):
[mediawiki/extensions/WikimediaMessages@master] Add Multilingual Wikisource to list of Wikidata's special sites

https://gerrit.wikimedia.org/r/660664

Change 660664 merged by jenkins-bot:
[mediawiki/extensions/WikimediaMessages@master] Add Multilingual Wikisource to list of Wikidata's special sites

https://gerrit.wikimedia.org/r/660664

Change 660796 had a related patch set uploaded (by Ladsgroup; owner: Ladsgroup):
[mediawiki/extensions/WikimediaMessages@wmf/1.36.0-wmf.28] Add Multilingual Wikisource to list of Wikidata's special sites

https://gerrit.wikimedia.org/r/660796

Change 660796 merged by jenkins-bot:
[mediawiki/extensions/WikimediaMessages@wmf/1.36.0-wmf.28] Add Multilingual Wikisource to list of Wikidata's special sites

https://gerrit.wikimedia.org/r/660796

Mentioned in SAL (#wikimedia-operations) [2021-02-01T13:50:54Z] <ladsgroup@deploy1001> Started scap: [[gerrit:660796|Add Multilingual Wikisource to list of Wikidata's special sites]] (T138332)

Mentioned in SAL (#wikimedia-operations) [2021-02-01T14:12:34Z] <ladsgroup@deploy1001> Finished scap: [[gerrit:660796|Add Multilingual Wikisource to list of Wikidata's special sites]] (T138332) (duration: 21m 52s)

okay we might need to postpone this since wmf.28 got cancelled and we need to wait until wmf.29 is deployed everywhere. I can instead backport it to wmf.27 (which would take 20 minutes in deployment ^ since rebuilding l10n is heavy). What do you think @Lydia_Pintscher ?

Yeah delaying until wmf.29 is deployed is fine.

We need to postpone it once more given that wmf.29 also got abandoned.

What’s the status of this task? wmf.30 also had issues at first but AFAIK it’s completely rolled out now.

I was mostly waiting for wmf.30 to stabilize because if we roll this out and then wmf.30 gets rolled back, main page of all wikis will break (had a similar situation with wikimaniawiki a couple of years ago) but I think it's safe to go later today or Monday. I probably deploy it later today.

Change 655428 merged by jenkins-bot:
[operations/mediawiki-config@master] Add sources to specialSiteLinkGroups Wikibase setting

https://gerrit.wikimedia.org/r/655428

Mentioned in SAL (#wikimedia-operations) [2021-02-23T12:15:44Z] <ladsgroup@deploy1001> Synchronized wmf-config/InitialiseSettings.php: [[gerrit:655428|Add sources to specialSiteLinkGroups Wikibase setting]] (T138332) (duration: 01m 00s)

So it's possible https://www.wikidata.org/w/index.php?title=Q4115189&diff=prev&oldid=1368215432
https://www.wikidata.org/w/index.php?title=Q79790&diff=prev&oldid=1368221137

I need to wait for a bit for caches to expire to make sure everything works fine.

Looks like it's working now

Yup: https://en.wiktionary.org/wiki/Wiktionary:News_for_editors

I’ve added some sitelinks, and noticed that no interlanguage links appear on multilingual Wikisource (interproject links work both on and pointing to multilingual Wikisource), see for example Template:NowCommons. Is it intended? Other multilingual wikis like Commons or Meta show interlanguage links to Wikipedia based on Wikidata. (Multilingual Wikisource should probably link to other Wikisources instead, but currently links to neither of them.)

If the community wants it, I think this can have a follow up ticket and be done. I don't know how commons does it but it looks like it should be possible.

Obviously the community wants it, that's how interlanguage links are supposed to work...
It it's really necessary, we can have a formal vote to show consensus, in the meantime can you please proceed with the follow-up ticket?

I created the follow-up ticket at T275958.

In T138332#6864016, @Ladsgroup wrote:

If the community wants it, I think this can have a follow up ticket and be done. I don't know how commons does it but it looks like it should be possible.

Through Module:Interwiki which creates old style wikitext for adding interwiki links based on Wikidata info.