Change 940385 had a related patch set uploaded (by Amire80; author: Amire80):

[mediawiki/extensions/MobileFrontend@master] Add several RTL languages: acm, ary, hno, ms-arab

https://gerrit.wikimedia.org/r/940385

Also documented in Manual:Adding_and_removing_languages: https://www.mediawiki.org/w/index.php?title=Manual%3AAdding_and_removing_languages&diff=6035456&oldid=6022265 .

Change 940385 merged by jenkins-bot:

[mediawiki/extensions/MobileFrontend@master] Add several RTL languages: acm, ary, hno, ms-arab

https://gerrit.wikimedia.org/r/940385

Why isn’t rtLanguages.js a generated package file? That’s exactly what generated files are for. The PHP code generating the file could go over the list of supported MediaWiki languages and generate the list on-the-fly, without the need for extra commits to the MF repo whenever a new language is added to core.

@Amire80 could you please add some QA steps so we can run this through QA next week?

In T342447#9038702, @Jdlrobson wrote:

This is a workaround for a performance issue in core. Ideally RTL information should be on the language links themselves but we had to revert https://gerrit.wikimedia.org/r/c/mediawiki/core/+/911367 due to a performance regression.

I believe using a generated package file could provide acceptable performance. Let’s continue at T342603: Generate the list of right-to-left languages automatically in MobileFrontend.