@Volker_E noticed `mediawiki.log.js` was being removed from his local MediaWiki install. After a lot of head scratching we realized his antivirus Comodo is quarantining the file because it is "Heur.Dual.Extensions" malware. If WIndows is configured to hide extensions, you see a benign-looking `mediawiki.log` file that would normally open in an editor, but in fact it's a potentially-executable JavaScript file. `resources/src` is full of other files named //something.other//`.js` but this is the only one that "masquerades" as a recognized filetype.
This has come up before, [[ https://www.mediawiki.org/wiki/Thread:Project:Support_desk/mediawiki.log.js_access_denied_when_backing_up_%28copying%29_mediawiki_folder | see old Support_desk thread]]. Also a web search for //"mediawiki.log.js" antivirus// shows lots of the generic ad-filled search results, suggesting that this file is triggering virus warnings on a wide enough scale for spammers to make fake pages for it :-) The fix is easy, rename this one file to `mediawiki.logger.js`
Surprisingly, his local MediaWiki install worked fine without this file until he tried using a different skin, then it silently failed with almost no JavaScript loaded. "Silently" as in no errors shown in browser console in regular or RL debug mode, all ResourceLoader requests successful, and I didn't see any error comments in RL responses; it wasn't until we enabled `wgDebugLogFile` and saw
[exception] [43c87615]
/load.php?debug=true&lang=de&modules=jquery%2Cmediawiki&only=scripts&skin=blueprint&version=80XVutC9 MWException
from line 850 of
D:\htdocs\Wikimedia\core\includes\resourceloader\ResourceLoaderFileModule.php:
ResourceLoaderFileModule::readScriptFiles: script file not found:
"D:\htdocs\Wikimedia\core/resources/src/mediawiki/mediawiki.log.js"
"Almost no JavaScript" as in the browser window has a `$` jQuery object but no `mw` or `mediaWiki` object, and so all MediaWiki JS enhancements are broken. It feels like a bug in RL that it should be so fundamentally broken without any indication in the browser, but maybe `mediawiki.log.js` is the file that would report these problems! :-)