Back compat for 5-year-old MU allowed_themes code

[nacin]

[20029] removed get_site_allowed_themes() and wpmu_get_blog_allowedthemes().

Both of these functions used an option key called allowedthemes that stored an array of allowed themes, keyed by stylesheet and valued with (int) 1.

Five years ago, there was an option called allowed_themes, that stored an array of allowed themes, keyed by untranslated theme name (like get_themes()) and again valued with (int) 1.

For more on this, see ​http://mu.trac.wordpress.org/changeset/936 (and in general you can search "allowedthemes" or "allowed_themes" on mu.trac, for more changesets and tickets).

We should consider adding some light back compat code to WP_Theme to support the old option.

[nacin]

[20144]

[scribu]

Light back-compat code... yeah.

How many old MU installs are there anyway?

[nacin]

In [20145]:

Only update the old allowed_themes network option from the main site admin or in the network admin. see #20103, #20146.

[nacin]

Replying to scribu:

Light back-compat code... yeah.

Well, it is light in terms of performance. The conditional will almost never be hit, and it ends up as a rolling upgrade, so isn't too bad.

How many old MU installs are there anyway?

This would hypothetically affect WP.com, but since they don't use blog-level allowed themes (except for VIPs, which don't go switching their theme anyway), they happen to be okay.

I remain tempted to strip this out; ryan too, I think. It's one of those situations that could get pretty nasty for users in the off chance a network is using it.

[nacin]

Talked with ryan a bit more. We could leave the rolling stuff for blogs, but add in upgrade code for networks. That will make half of this disappear. Still tempting to eliminate the blog stuff too, but since we've always had it...

[nacin]

In [20148]:

The allowed_themes rolling upgrade for individual sites should not add empty allowedthemes arrays. If there are no allowed themes, don't add an empty option. Move the network rolling upgrade to upgrade_network(). see #20146.