wp_query gets poisoned by new WP_Query objects

[Denis-de-Bernardy]

See #7080 and #9458 for reference material.

Code to duplicate the issue:

while ( have_post() ) {
  the_post();
  the_title();
  the_widget('WP_Widget_Recent_Posts');
  the_content();
}

In the Recent Posts widget, add the following after the_post() to see things happening:

var_dump($GLOBALS['wp_the_query']->post->ID);

You'll notice is changes for no obvious reason.

[jacobsantos]

Fix for Recent Posts widget.

[ryan]

Could we not use get_posts() here, do a regular foreach loop, and pass IDs/objects to the template functions?

[jacobsantos]

Ryan, thou be a genius.

[Denis-de-Bernardy]

we could, and it might fix it, but there would remain the underlying issue -- i.e. why is wp_the_query getting changed at all? ;-)

D.

[ryan]

(In [11382]) Break global post ref so we don't pollute queries. see #9854

[ryan]

WP::register_globals() does this:

$GLOBALS['post'] = & $wp_query->post;

Either removing that ref or breaking the ref in the_post() helps. Opted for ref break in [11382].

[Denis-de-Bernardy]

good catch. will give it a shot. say, isn't this more prudent?:

unset($GLOBALS['post']);
global $post;

[ryan]

Probably. Will redo.

[ryan]

(In [11386]) Unset from GLOBALS. see #9854

[jacobsantos]

I wonder, does this fix it?

[ryan]

I think it should. Just waiting confirmation.

[Denis-de-Bernardy]

Confirming it does, but I'd like to request an additional tweak in order to spare myself a few nightmares with a separate plugin. Patch coming up in a sec.

[Denis-de-Bernardy]

the suggested additional patch is to allow plugins to decide whether to do anything on loop_start/loop_end based on whether it's the main loop or not.

[Denis-de-Bernardy]

see also #9256

[ryan]

(In [11399]) Pass query object to loop_start and loop_end actions. Props Denis-de-Bernardy. fixes #9854

[ryan]

Reports of breakage for loops like this:

$recent = new WP_Query("blah=blah");
while($recent->have_posts()) {
  $recent->the_post();
  echo $post->ID;
}

Evidently, $post is not being set.

[Denis-de-Bernardy]

on to it right away

[Denis-de-Bernardy]

mm, anything more specific? because this essentially is exactly what the recent posts widget does. :-P

[ryan]

Sent examples your way. Working on boiling it down to a test case.

[ryan]

The problem loop is in sidebar.php, which is loaded through get_sidebar() -> load_template(). load_template() sets up a $post global for use by sidebar.php, but we're stomping that global.

[ryan]

global $post creates a ref. We unset GLOBALSpost? in the_post(). The global $post used by sidebar.php now points at nothing.

[ryan]

Stick a loop in sidebar.php of the default theme to see:

$recent = new WP_Query('showposts=10');
while ( $recent->have_posts() ) {
	$recent->the_post();
	var_dump($post);
}

$post never changes

[ryan]

Removing the ref from WP::register_globals() seems to fix everything. We can keep global $post as a ref for everyone to use without it messing with queries.

[Denis-de-Bernardy]

seems right. will give it a shot tomorrow.

[Denis-de-Bernardy]

first bit of the patch isn't necessarily useful though.

[Denis-de-Bernardy]

uploaded a diff for test cases and a slightly different patch (I moved the new the_post hook to a place where it's more useful on singular pages)

[Denis-de-Bernardy]

The other refs in WP::register_globals() might want the same kind of treatment at some point, too.

[ryan]

(In [11406]) Remove global regs that can poison query objects. fixes #9854