TL;DR: We're starting to remove long-deprecated methods. First, they'll be wrapped in mw.log.deprecate (possibly replaced with dummy values) which will produce a stacktrace to the console when used. Example: http://cl.ly/image/3W0o131K0D3j

Pre-amble:

* As of MediaWiki 1.17 we started actively developing new javascript features. * Any code from before that point has been tagged "legacy" and deprecated as of v1.17.0 back in 2011.

Problems:

* There is no easy way to see whether a page is using any of these deprecated interfaces. * We still haven't removed any of the legacy code. * Though we've added new things (jQuery, jQuery UI, mw.Title, mw.Uri etc.). We've been reluctant to iterate further on these "new" things and haven't been able to really refactor or improve them.

We've upgraded jQuery and jQuery UI a few times. But only because there were no major changes in backwards compatibility. This changed in 1.9 and that's why we're still on 1.8.

It would seem we're in a fixed position – unable to move up, only sideways. On the server-side of MediaWiki, deprecation has been a natural process enforced socially (plugins not maintained for several release cycles will simply have to be disabled). We introduce the new, we migrate uses of the old, we deprecate the old, we support both for uses for a while to allow others to migrate their stuff, then we remove the old.

In the front-end we never completed such a cycle. But, we're getting close to the completion of our first first cycle now. The legacy scripts deprecated as of v1.17.0 have all been removed or wrapped in mw.log.deprecate.

Please go to your favourite wiki in debug=true mode with a modern browser (recent Chrome, Firefox or Opera) and look at the console. Look for any uncaught exceptions, deprecation notices or other messages and try to address them soon (or report it to the maintainers of the gadgets triggering them).

-- Krinkle

[1] https://doc.wikimedia.org/mediawiki-core/master/js/#!/api/mw.log-method-depr...