Change 879670 had a related patch set uploaded (by Func; author: Func):

[mediawiki/skins/Vector@master] LanguageDropdown:

https://gerrit.wikimedia.org/r/879670

Change 879670 merged by jenkins-bot:

[mediawiki/skins/Vector@master] LanguageDropdown: Check if the page is in talk namespaces instead

https://gerrit.wikimedia.org/r/879670

This should be backported as soon as possible since wikis like French Wikipedia currently don’t have language switching at their main pages:
https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Accueil_principal
Tagging @Jdlrobson to make sure that happens.

Tagging @santhosh and language team as I'm not too familiar with the work they are doing here.

It seems that, although the merged change fixes the issue somewhat, the code in question should be rewritten to check if there are any interwiki data for the page, as opposed to just making assumptions about what page can link to other languages and what page cannot. Judging by how interwiki links act when on talk pages (example in ruWP, usually [[en: type link creates an interwiki link, but that doesn’t happen on a talk page), that kind of limitation might already exist somewhere and maybe can be referenced as a more reliable way to know what pages are allowed to have interwiki links.

In T326788#8524690, @stjn wrote:

This should be backported as soon as possible since wikis like French Wikipedia currently don’t have language switching at their main pages:
https://fr.wikipedia.org/wiki/Wikip%C3%A9dia:Accueil_principal

There are no backport windows recently, otherwise, I would have added this patch to the calendar.
Is next Tuesday soon enough? I will be around if no one claim to be there during deployment.

This might qualify for emergency deployment tbh. Main pages are extremely visible parts of Wikimedia projects, and a number of them are in a non-content namespace [1] and don’t have interwiki links right now if new Vector is the default skin. But if it doesn’t, then Tuesday is fine, I suppose.

[1]: https://www.wikidata.org/wiki/Q5296 for the list of all main pages, from what I can spot, French, Esperanto, Javanese, Portuguese Wikipedias currently have it broken

Just to show the extent of the bug, as reported here on fawikipedia, all non-article namespaces on English and Persian (Farsi) Wikipedia have their language links missing and "Page contents not supported in other languages" is shown in place of the list of language links (for example, w:en:Template:Deep fried foods which has a corresponding template in fawikipedia and the link can be seen using vector legacy skin).

The same problem applies to namespaces except "main" on Wikisources (i.e. Help).
When the "vector 2022" skin is used, the message "Page contents not supported in other languages." appears instead of links:
see:
https://en.wikisource.org/wiki/Help:Contents?useskin=vector
vs
https://en.wikisource.org/wiki/Help:Contents?useskin=vector-2022
or
https://pl.wikisource.org/wiki/Pomoc:Spis_tre%C5%9Bci?useskin=vector
vs
https://pl.wikisource.org/wiki/Pomoc:Spis_tre%C5%9Bci?useskin=vector-2022

This is especially annoying on the wiki, where vector 2022 is the default already (ie. pl ws).

Interestingly, in "vector-2022" the Sticky header shows the actual number of links, but... no links, and the message is: "No languages yet. No languages are available for now":

This is also discussed in T316559.

Yes, the issue that caused this is already fixed on the side of the code, you don’t need to document it further. What we need now is to deploy the patch ASAP.

Change 879798 had a related patch set uploaded (by Func; author: Func):

[mediawiki/skins/Vector@wmf/1.40.0-wmf.18] LanguageDropdown: Check if the page is in talk namespaces instead

https://gerrit.wikimedia.org/r/879798

In T326788#8526494, @RhinosF1 wrote:

Hi,

Can someone from SRE or releng please look to facilitate an emergency deploy?

I am close by my computer for a bit if there's someone who can help me verify the fix.

I'm around in my capacity as SRE. Going to help on this.

Change 879798 merged by jenkins-bot:

[mediawiki/skins/Vector@wmf/1.40.0-wmf.18] LanguageDropdown: Check if the page is in talk namespaces instead

https://gerrit.wikimedia.org/r/879798

Mentioned in SAL (#wikimedia-operations) [2023-01-16T01:05:09Z] <thcipriani@deploy1002> Started scap: Backport for [[gerrit:879798|LanguageDropdown: Check if the page is in talk namespaces instead (T316559 T326788)]]

Mentioned in SAL (#wikimedia-operations) [2023-01-16T01:15:17Z] <thcipriani@deploy1002> thcipriani and func: Backport for [[gerrit:879798|LanguageDropdown: Check if the page is in talk namespaces instead (T316559 T326788)]] synced to the testservers: mwdebug1001.eqiad.wmnet, mwdebug2001.codfw.wmnet, mwdebug1002.eqiad.wmnet, mwdebug2002.codfw.wmnet

I'd appreciate an incident report on this: https://wikitech.wikimedia.org/wiki/Incident_status Why it passed the tests and QA, why it reached production, why the fix took too long to be deployed, and so on.

Mentioned in SAL (#wikimedia-operations) [2023-01-16T01:29:57Z] <thcipriani@deploy1002> Finished scap: Backport for [[gerrit:879798|LanguageDropdown: Check if the page is in talk namespaces instead (T316559 T326788)]] (duration: 24m 47s)

The deployment went way bumpier than anticipated. I assume a portion of codfw mw nodes didn't get the php-fpm reboot and might still be shown in small subset of users. In a couple of hours, the Europe wakes up and we can take a look.

More context: T327041

Change 880423 had a related patch set uploaded (by Nik Gkountas; author: Nik Gkountas):

[mediawiki/extensions/UniversalLanguageSelector@master] ULS: Display "Page contents not supported" body in missing and talk pages

https://gerrit.wikimedia.org/r/880423

Change 880423 merged by jenkins-bot:

[mediawiki/extensions/UniversalLanguageSelector@master] ULS: Display "Page contents not supported" body in missing and talk pages

https://gerrit.wikimedia.org/r/880423