@Meno25: Hi, how is this related to Cognate (as that is mentioned nowhere in the task description)?
Removing All-and-every-Wiktionary as this is about one single website - see its project description.

In T259360#6353392, @Aklapper wrote:

@Meno25: Hi, how is this related to Cognate (as that is mentioned nowhere in the task description)?
Removing All-and-every-Wiktionary as this is about one single website - see its project description.

Hi. I wrote this task description quickly (as I had other things to do at that time), so, I didn't put much thought about how it should be categorized. Feel free to recategorize the task as needed.

Aha! Thank you. Now it makes sense.

Somehow shywiktionary is not added to Cognate database (it's enabled there though):

ladsgroup@mwmaint1002:~$ mwscript mysql.php --wiki=shywiktionary --cluster extension1 --wikidb cognate_wiktionary
wikiadmin@10.64.32.11(cognate_wiktionary)> select * from cognate_sites where cgsi_dbname = 'shywiktionary' limit 5;
Empty set (0.00 sec)

wikiadmin@10.64.32.11(cognate_wiktionary)> select * from cognate_sites where cgsi_dbname = 'frwiktionary' limit 5;
+---------------------+--------------+----------------+
| cgsi_key            | cgsi_dbname  | cgsi_interwiki |
+---------------------+--------------+----------------+
| 2097444195020099748 | frwiktionary | fr             |
+---------------------+--------------+----------------+
1 row in set (0.00 sec)

Mentioned in SAL (#wikimedia-operations) [2020-08-17T21:57:31Z] <Amir1> ladsgroup@mwmaint1002:~$ mwscript extensions/Cognate/maintenance/populateCognateSites.php --wiki=aawiktionary --site-group wiktionary (T259360)

So it's there now and if you don't see it, you just need to purge the parser cache. Here's an example: https://fr.wiktionary.org/wiki/yila

As you can see, The rendering is sorta broken, it can be because it's not in the interwiki sorting order or the fact that core doesn't have the language name for shy (It has it for shy-latn though, you can find the list in languages/data/Names.php). But this is out of Wikidata team now. I think @Amire80 and the languages team should handle the rendering ( I tried adding it to the interwiki sorting php file but it's really complicated).

What parser cache is meant? Some pages still don't have inverse links: https://shy.wiktionary.org/wiki/tacawit

Note that this is still a problem even when interlanguage links are "manually" added to pages. For example, adding the link "[[shy:raisin]]" on (say) the German Wiktionary entry for "raisin" results in the wikilink "shy:raisin" showing up in the page content rather than creating an interlanguage link in the sidebar, whereas adding, say, [[af:raisin]] there does result in an interlanguage link in the sidebar (note that there's no such page in the afwiktionary, but that's beside the point). Does this mean it's not purely a Cognate issue? (I have no idea.)

Oh clearly something is wrong with shy language setup. Look at sitematrix (https://meta.wikimedia.org/wiki/Special:SiteMatrix)

I check and see what's going on there.

Change 667757 had a related patch set uploaded (by Ladsgroup; owner: Ladsgroup):
[mediawiki/core@master] Add shy to list of special languages mapping to shy-Latn

https://gerrit.wikimedia.org/r/667757

Mentioned in SAL (#wikimedia-operations) [2021-03-02T05:40:32Z] <Amir1> apply gerrit:667757 on mwdebug1002 to test T259360

I confirm the patch above fixes the problem.

Without it

MediaWiki\MediaWikiServices::getInstance()->getLanguageNameUtils()->getLanguageName('shy',MediaWiki\Languages\LanguageNameUtils::AUTONYMS,MediaWiki\Languages\LanguageNameUtils::DEFINED);

returns empty (this is part of Parser.php) but with the patch, it returns the name of shywiki and having it checked out locally makes the link to go in sidebar (language links) but without it, is like the issue mentioned above.

All being said and being done, Wikidata team is not responsible for issues handling edge case languages and their setup...

Change 667757 merged by jenkins-bot:
[mediawiki/core@master] Add shy name (same as shy-latn)

https://gerrit.wikimedia.org/r/667757

I'll backport this and rebuild the interwiki cache tomorrow (hopefully, If I can find some time in meetings, if not, I'll do it on Thursday).

Change 670350 had a related patch set uploaded (by Ladsgroup; owner: Ladsgroup):
[mediawiki/core@wmf/1.36.0-wmf.34] Add shy name (same as shy-latn)

https://gerrit.wikimedia.org/r/670350

Change 670351 had a related patch set uploaded (by Ladsgroup; owner: Ladsgroup):
[mediawiki/core@wmf/1.36.0-wmf.33] Add shy name (same as shy-latn)

https://gerrit.wikimedia.org/r/670351

Change 670351 merged by jenkins-bot:
[mediawiki/core@wmf/1.36.0-wmf.33] Add shy name (same as shy-latn)

https://gerrit.wikimedia.org/r/670351

Mentioned in SAL (#wikimedia-operations) [2021-03-10T12:22:02Z] <ladsgroup@deploy1002> Synchronized php-1.36.0-wmf.33/languages: [[gerrit:670351|Add shy name (same as shy-latn)]] (T259360) (duration: 01m 10s)

Change 670350 merged by jenkins-bot:
[mediawiki/core@wmf/1.36.0-wmf.34] Add shy name (same as shy-latn)

https://gerrit.wikimedia.org/r/670350

Mentioned in SAL (#wikimedia-operations) [2021-03-10T12:34:25Z] <ladsgroup@deploy1002> Synchronized php-1.36.0-wmf.34/languages: [[gerrit:670350|Add shy name (same as shy-latn)]] (T259360) (duration: 01m 10s)

Mentioned in SAL (#wikimedia-operations) [2021-03-11T21:57:26Z] <Amir1> run populate pages in cognate (T259360)