[wp-trac] [WordPress Trac] #20699: AJAX Actions now passes the action name as an arg

[WordPress Trac]

#20699: AJAX Actions now passes the action name as an arg
----------------------------+--------------------------------------
 Reporter:  sivel           |      Owner:
     Type:  defect (bug)    |     Status:  new
 Priority:  normal          |  Milestone:  3.4
Component:  Administration  |    Version:  3.4
 Severity:  normal          |   Keywords:  2nd-opinion dev-feedback
----------------------------+--------------------------------------
 Previous to the admin-ajax.php refactoring in #15327 the do_action calls
 looked like:

 {{{
 do_action( 'wp_ajax_nopriv_' . $_REQUEST['action'] );
 do_action( 'wp_ajax_' . $_GET['action'] );
 do_action( 'wp_ajax_' . $_POST['action'] );
 }}}

 They now look like:

 {{{
 do_action( 'wp_ajax_' . $_REQUEST['action'], $_REQUEST['action'] );
 do_action( 'wp_ajax_nopriv_' . $_REQUEST['action'], $_REQUEST['action'] );
 }}}

 The change is to add the action name as an argument to do_action to pass
 to the callback, where before there was none.

 As a result,plugin authors were previously able to rely on passing an arg
 to determine if the function was called by an ajax action or not based on
 if the $arg was empty.  Now the $arg is always populated, as we are
 sending the action name as the argument, instead of allowing do_action to
 send it's default empty string.

 I had multiple plugins affected by this, where I was determining if the
 call to the function was from the ajax call, and performing different
 tasks.  I don't have a problem with fixing it in my code, to perhaps do it
 the right way like it should have been done from the beginning, but I am
 worried that it could potentially cause issues with other plugins that may
 be doing this.

 Some sample code that started failing:

 {{{
 add_action( 'wp_ajax_nopriv_sivel', 'sivel' );
 function sivel( $arg ) {
         if ( $arg )
                 // Do something if an arg was passed
         else
                 // Do something if an arg was not passed
 }
 }}}

 In the above example, only the code under {{{if ( $arg )}}} is executed
 since 3.4. Switching to something like {{{if ( $arg === true )}}} fixes
 the issue in the plugin.

 I also realize that passing the action as an arg gives us context for a
 single callback called from multiple ajax actions, but that could also be
 retrieved using {{{$_REQUEST['action']}}} from the callback anyway.

 In case we should remove it, I've attached the diff.

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Ticket URL: <http://core.trac.wordpress.org/ticket/20699>
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