[wp-trac] [WordPress Trac] #38011: WP_Hook class late assignment behavior change

[WordPress Trac]

#38011: WP_Hook class late assignment behavior change
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 Reporter:  salcode       |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Plugins       |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
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 The recent addition of the `WP_Hook` class has introduced a change in
 behavior when a function is added to the currently executing action with
 an earlier priority than that which is currently being executed.

 '''Example'''

 The following code defines a shortcode `[WP_Hook_priority_example]`

 {{{#!php
 <?php

 add_shortcode( 'WP_Hook_priority_example', 'wp_hook_priority_example' );

 function wp_hook_priority_example() {
         add_action( 'wp_hook_priority_example', 'add_other_functions' );
         do_action( 'wp_hook_priority_example' );
 }

 // This function is called with a priority of 10 on the hook
 `wp_hook_priority_example`.
 function add_other_functions() {

         add_action( 'wp_hook_priority_example', 'print20', 20 );

         // Assign print5() to priority 5 (even though priority 5 has
 passed already).
         add_action( 'wp_hook_priority_example', 'print5', 5 );

 }

 function print5() { echo '<p>5</p>'; }
 function print20() { echo '<p>20</p>'; }
 }}}

 '''Prior to the Introduction of the WP_Hook Class'''

 This code will output

 {{{
 20
 5
 }}}

 For clarification, I don't think this is a logical behavior but it is the
 current behavior in WordPress 4.6 and earlier.

 Even though we are executing code assigned to `wp_hook_priority_example`
 with '''priority''' `10`, when we assign a function to the same hook using
 a priority that has passed (e.g. `5`) the function is still executed.

 '''After the Introduction of the WP_Hook Class'''

 This same shortcode executed after the introduction of the WP_Hook class
 displays only

 {{{
 20
 }}}

 I believe this is the more logical behavior, however in terms of backwards
 compatibility I believe it is worth considering making this behavior
 consistent with the previous versions of WordPress.

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Ticket URL: <https://core.trac.wordpress.org/ticket/38011>
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