'allowedthemes' network option never gets primed when themes are deleted

[DrewAPicture]

It appears that the 'allowedthemes' network option is channeling Rick Astley in that it never gives up or lets down, or runs around and deserts the themes it stores.

In my testing, it would seem that all themes ever installed are stored in perpetuity. It's possible this behavior has been around since WP_Theme was written in 3.4.

For example: I ran across this bug when testing something unrelated, and noticed that 'allowedthemes' contained 303 total keys (I have ~10 themes on my test build currently).

[DrewAPicture]

Needs a patch first, this one's been around for a while anyway.

[jeremyfelt]

Once #30594 is in, we'll have WP_Network::network_disable_theme() available to us. 34182.diff​ implements this in delete_theme().

Unit tests on this might be tough. We don't have anything covering delete_themes() at the moment.

[jeremyfelt]

In 37203:

Multisite: Remove theme from network allowed themes when deleted

Previously, a deleted theme would remain in the list of allowed themes until manually cleared. This uses WP_Theme::network_disable_theme(), added in [37202].

Fixes #34182.