This is likely not going to get done since the extension is not deployed on Wikimedia so would have to pass the lengthy https://www.mediawiki.org/wiki/Writing_an_extension_for_deployment process.

I doubt that extension is compatible with the parser cache setup on Wikimedia wikis.

May I ask which problem are you trying to solve with this extension?

See also: T47455: Cleanup and enable UserFunctions extension on wikitech

I would like to have/use a "magic word" (template/function) to get the username of the account that is currently logged in -- to be able to use it as a parameter/suffix in a semi-dynamic URL.

Example:

[[wmfdashboard:users/{{#username:alt}}|My impact]]

That use case got declined in the past in T6196: New user-specific variable (magic word, parser function) giving {{USERNAME}} ({{CURRENTUSER}} {{USER}}).

I understand that MediaWiki core functions in this context have a negative impact on cache performance.

Only using jQuery, I got the following result, using a page, a template, and a Common.js:

[[wmfdashboard:users/{{wgUserName}}|My impact]]

[[wmfdashboard:users/Geertivp|My impact]]

Template:wgUserName:

<span id="wgUserName"></span>

<span>Geertivp</span>

What I would like to get is:

Geertivp

MediaWiki:Common.js:

$( function( $ ) {
 var TagId = document.getElementById("wgUserName");
 var UserName = mw.config.get('wgUserName');

 if (TagId !== null && UserName !== null) {
  TagId.innerText = UserName;
 }

} );

Who could provide me with the missing logic to remove the <span> result, because this is messing up the URL syntax?

How does wp.fr show my username?
https://fr.wikipedia.org/wiki/Wikipédia:Accueil_principal

In T387042#10613067, @Geertivp wrote:

How does wp.fr show my username?
https://fr.wikipedia.org/wiki/Wikipédia:Accueil_principal

I believe that’s because the software passes the name of the currently logged-in user as a variable to the mainpage-title-loggedin system message (which is locally defined as Bienvenue $1).