[wp-trac] [WordPress Trac] #36199: Calling do_action within the same action causes next priority block to be skipped.

[WordPress Trac]

#36199: Calling do_action within the same action causes next priority block to be
skipped.
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 Reporter:  dougwollison  |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Plugins       |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
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 The do-while loop that `do_action()` and `apply_filters()` use—rather than
 a foreach loop—to iterate over the the hooks for an action/filter seems to
 cause some issues that can result in the callbacks in the next priority
 block to be skipped altogether.

 For example, a theme I was testing something with called `get_posts()`
 within the `pre_get_posts` action so it could get a list of posts to
 exclude from the main query. Since that function calls the same action,
 the current handling of do_action and apply_filters (and their ref_array
 version) causes the filter list to be reset in the middle of it being
 performed, causing the next priority block to be skipped.

 The same issue occurs when a callback removes itself to prevent an
 infinite loop and fails to re-add itself when it's done (though this can
 be blamed on programmer error for having it remove itself before the
 should-proceed check).

 The only way around the issue without messing with core code would be to
 add throwaway hooks as a buffer between the known offending hooks, which
 frankly is ridiculous.

 I've attached two patches made to `plugin.php` on trunk; one copies the
 `$wp_filter[$tag]` to a new variable to be iterated over in the do-while
 loop, and the other replaces the do-while loop with a foreach loop. I feel
 the later is the better option but I can't be sure there wasn't good
 reason for using the do-while loop in the first place. Both also include
 some code cleanup; adding curly braces to the various blocks that aren't
 using them.

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Ticket URL: <https://core.trac.wordpress.org/ticket/36199>
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