jQuery update strategy
WordPress is moving forward with a roadmap for updating its shipped version of jQuery and the jquery-migrate polyfill that has historically provided backward compatibility. See https://make.wordpress.org/core/2020/06/29/updating-jquery-version-shipped-with-wordpress/
This change will almost certainly cause many regressions across plugins and themes that use jQuery on the Commons. We need a strategy to deal with this.
As a starting place, it might be helpful to distinguish between a couple different kinds of cases:
1. Some plugins and themes don't use jQuery at all.
2. Some of our most popular themes and plugins - things like Jetpack, for example - are well-maintained, and will receive upstream updates that ensure compatibility. It's very likely that these will be fixed before the relevant WP update, and we don't need to worry about them here on the Commons.
3. The majority of plugins and themes on the Commons are either poorly maintained or unmaintained. For those in this category that use jQuery, some will probably be OK even after the jQuery update.
4. The remaining plugins and themes will break in ways large and small.
As a first step, we should try to detect which plugins/themes use jQuery (eliminating those in category 1). This should be easy. From there, it would be nice if we had an automated tool for identifying - at least in a preliminary fashion - which themes/plugins will be negatively affected. (I assume that there's something akin to PHPCS for this purpose. Does anyone know of anything?) Once we have a list, we can make some decisions about next steps.