Allow to adjust the `$in_admin` property of `WP_Screen`

[flixos90]

The $in_admin property of the WP_Screen class is impossible to be changed by a developer at the moment, which makes sense in how WordPress uses it.

However, I'm currently building a plugin that creates an additional administration panel (like network and user admin) and I would need to adjust the $in_admin property to reflect when this panel is active. Otherwise a function like is_blog_admin() returns true although we actually aren't in the regular admin panel (since the value of $in_admin defaults to 'site').

So I'm proposing to either make the property public so that a developer can override it (for example on the current_screen action) or to add a new filter for the property specifically in WP_Screen::get(). I would prefer the second approach since having the property being protected makes sense in general. The use-case I have is a very rare one, so I think a very specific filter for it should do.

[flixos90]

37445.diff​ introduces such a filter. I'm not sure about whether the name of that filter is the best possible choice though, so feel free to come with something more accurate.

[flixos90]

For reference: Implementing the proposal from #37526 would make this ticket invalid/unnecessary.

[peterwilsoncc]

@flixos90 this came up in a triage session today, is it something you're still interested in pursuing?

[flixos90]

@peterwilsoncc Thanks for the ping. I'm no longer working on an implementation of a separate administration panel at this point, but if anybody else is, I still think this filter would be handy.

It's certainly a lower-hanging fruit, but IMO it is worth adding because it facilitates the use-case of building out separate administration panels. While the impact outside of it is practically non-existent, it is technically trivial so I'm in favor of doing it.

@johnjamesjacoby @jeremyfelt Still interested in "global admin"? :)

[johnjamesjacoby]

Replying to flixos90:

@johnjamesjacoby @jeremyfelt Still interested in "global admin"? :)

Yeah you know me 🎶

[desrosj]

Re-adding a milestone to this one. Was lost along the way somewhere.

This PR introduces a new filter, screen_admin_context, to the WP_Screen class, enabling developers to modify the $in_admin property dynamically. This property is currently locked to specific values (such as 'site' for regular site admin and 'network' for network admin), making it challenging to accurately identify additional custom administration panels introduced by plugins.

Trac ticket: https://core.trac.wordpress.org/ticket/37445

[geekofshire]

@desrosj @flixos90  I have raised a PR for this ticket, please give it a look. Thanks