[wp-trac] [WordPress Trac] #17817: do_action/apply_filters/etc. recursion on same filter kills underlying call

[WordPress Trac]

#17817: do_action/apply_filters/etc. recursion on same filter kills underlying call
-------------------------------------------------+-------------------------
 Reporter:  kernfel                              |       Owner:  nacin
     Type:  defect (bug)                         |      Status:  reviewing
 Priority:  normal                               |   Milestone:  4.4
Component:  Plugins                              |     Version:  2.2
 Severity:  normal                               |  Resolution:
 Keywords:  has-unit-tests has-patch needs-      |     Focuses:
  testing                                        |
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Comment (by jbrinley):

 Thanks for testing, @ocean90. Those errors are disheartening. There's
 really no way to be 100% backwards compatible with something that touches
 so deeply into the internals of `$wp_filter`. bbPress could be revised to
 work with both the old and the new `$wp_filter` with code such as:

 {{{
 function bbp_get_template_stack() {
         global $wp_filter, $merged_filters, $wp_current_filter;

         // Setup some default variables
         $tag  = 'bbp_template_stack';
         $args = $stack = array();

         // Add 'bbp_template_stack' to the current filter array
         $wp_current_filter[] = $tag;

         if ( class_exists( 'WP_Hook' ) ) {
                 $filter = $wp_filter[ $tag ]->callbacks;
         } else {
                 $filter = &$wp_filter[ $tag ];

                 // Sort
                 if ( ! isset( $merged_filters[ $tag ] ) ) {
                         ksort( $filter );
                         $merged_filters[ $tag ] = true;
                 }
         }

         // Ensure we're always at the beginning of the filter array
         reset( $filter );

         // Loop through 'bbp_template_stack' filters, and call callback
 functions
         do {
                 foreach ( (array) current( $filter ) as $the_ ) {
                         if ( ! is_null( $the_['function'] ) ) {
                                 $args[1] = $stack;
                                 $stack[] = call_user_func_array(
 $the_['function'], array_slice( $args, 1, (int) $the_['accepted_args'] )
 );
                         }
                 }
         } while ( next( $filter ) !== false );

         // Remove 'bbp_template_stack' from the current filter array
         array_pop( $wp_current_filter );

         // Remove empties and duplicates
         $stack = array_unique( array_filter( $stack ) );

         return (array) apply_filters( 'bbp_get_template_stack', $stack ) ;
 }
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/17817#comment:158>
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