Feature summary (what you would like to be able to do and where):

There should be a way for pages (typically templates) to easily get the direction for a language code or script code.

For example, there could be a parser function such as {{#dir:...}}:

• {{#dir:en}} would produce "ltr".
• {{#dir:ar}} would produce "rtl".
• {{#dir:Arab}} would produce "rtl".
• {{#dir:und-arab}} would produce "rtl".

If the input is a language code without a script code, it would return the direction MediaWiki has for that language.

If the input is a language code with a script code, or just a script code, it would return the direction for that script code.

MediaWiki does not currently have data about scripts, but it could get it from CLDR, which provides data about scripts generated from Unicode data (main repository, JSON repository).

They currently list 35 scripts as rtl: Adlm Arab Armi Avst Chrs Cprt Elym Hatr Hebr Hung Khar Lydi Mand Mani Mend Merc Mero Narb Nbat Nkoo Orkh Ougr Palm Phli Phlp Phnx Prti Rohg Samr Sarb Sogd Sogo Syrc Thaa Yezi

There are also a few variants of those scripts which don't get included in CLDR's data: Aran, Syre, Syrj, Syrn

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):

Wiki pages often want to include words in other languages. Multilingual wikis often have translatable elements on pages and need to make sure the direction is set correctly.

There are many wikis with templates like Template:Dir (https://www.wikidata.org/wiki/Q14412446), most of which hardcode an outdated list of language codes.

Lots of wikis have modules with lists of rtl scripts (global search) and functions to return the direction (global search).

mw.language:getDir() in Lua is often not suitable because it's not easily accessible from a template without first writing a module, it only supports the languages included in MediaWiki, and it's easy to run into the limit on how many times you can use it on a single page.

Benefits (why should this be implemented?):

It would reduce the amount of maintenance needed and improve consistency across wikis (wikis would not need lists of rtl scripts, if a new rtl script is added to Unicode, it would only need to be added to one place for the data to become available to all wikis).

Supporting script codes and languages with script codes would improve support for languages not yet included in MediaWiki.

It might also be more efficient to fetch the direction from the script (when provided) by looking up scripts in a relatively short list of script codes.

Note {{Dir}} is currently the most used template in Commons. See also: T343131: Commons database is growing way too fast