Hello,
Now Lua has access to the internal fallback sequences of MediaWiki [1], so this can be used to gracefully degrade the translation of the templates included in a page, by the means of {{Translatable template}} (also called {{TNT}}) or auto-translated templates which use {{Fallback}}, mainly on Commons. I worked on this yesterday [2].
But I send this message mainly to show the comparison between the fallback sequences of Commons vs MediaWiki [3].
I guess some fallback sequences of Commons could be added to MediaWiki: * af -> nl * br -> fr (not sure) * ckb -> fa * en-gb -> en * fy -> nl
There is one conflicting fallback sequence: * co -> fr (Commons) or it (MediaWiki)
And some differences: * pdt -> nds, de (Commons) or de (MediaWiki) * nds -> nds-nl, de (Commons) or de (MediaWiki) * nds-nl -> nds, nl (Commons) or nl (MediaWiki)
And more importantly, the purposes of the fallback sequences are a bit different inside a same language family/variant family: MediaWiki specializes from general to variants (often by script), but Commons does the opposite: degrades from variants to general. I find a feature could be added in the Translate extension to give access to these "reverse fallback sequences" by comparison to MediaWiki’s ones. This could be implemented either by creating a small database (perhaps add the opposite parameter of $fallback in the MessagesXX.php) either by computing these. This could be used for the translation of the templates, in Special:MyLanguage [bug 48292], and to redirect the translators to the general language (the messages "Translate in zh please." in $wgTranslateBlacklist of CommonSettings.php in Wikimedia config).
[1] https://gerrit.wikimedia.org/r/101910 [2] https://meta.wikimedia.org/wiki/Module_talk:Template_translation#Fallback [3] https://commons.wikimedia.org/wiki/Template_talk:Fallback#Comparison_of_the_... [bug 48292] https://bugzilla.wikimedia.org/48292
~ Seb35