[wp-trac] [WordPress Trac] #38645: Improve roles reinit when switching between sites

[WordPress Trac]

#38645: Improve roles reinit when switching between sites
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 Reporter:  johnjamesjacoby  |      Owner:
     Type:  defect (bug)     |     Status:  new
 Priority:  normal           |  Milestone:  Awaiting Review
Component:  Role/Capability  |    Version:  trunk
 Severity:  normal           |   Keywords:  has-patch needs-testing early
  Focuses:  multisite        |
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 When switching between sites (since r39083) the `$wp_roles` global is
 being recreated instead of adjusting the values of the existing global.

 The current regression means if a plugin was keeping its own copy of the
 `$wp_roles` global around (maybe as a property in a class, or for some
 other convenience sake) then then newly created `$wp_roles` global no
 longer points to that same copy. (See #23016 for more details & examples.)

 History lesson: previous to that changeset, the `reinit()` method was used
 to update the roles for the witched site. That method was largely a copy
 of the `_init()` method, and was purpose built for blog switching.

 ----

 Anecdotally, it's unlikely this will cause very many problems, but it is
 still a regression from previous behavior, and I believe the fix is fairly
 straightforward.

 We can take inspiration from the `WP_User::for_blog()` method, and
 introduce a `for_blog()` method to the `WP_Roles` class to basically do
 the exact same thing in the exact same way. We can make alterations to the
 blog switching functions to update the `$wp_roles` and
 `$current_user->roles` values in unison.

 Architecturally, I think it makes sense to call these methods together,
 but not have one call the other all the time, because there may a reason
 or time where that control is welcome, and marrying them together now
 makes divorcing them later difficult.

 Patch imminent.

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Ticket URL: <https://core.trac.wordpress.org/ticket/38645>
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