Check if index in $args isset / ! empty before using it in Walker_Comment methods or create default $args in case if it is empty

[oglekler]

Taking into account the comments in #53449, I suggest local fix for the comments walker (wp-includes/class-walker-comment.php).

Class Walker_Comment uses some $args indexes without checking if they exist. And in my case, they don't exist, $args are empty array and I am getting notices. I will consider adding $args into the call, but they are commented as optional and don't suppose to be used in such way.

Examples:

public function start_el uses:

$args['short_ping']
$args['format']

And

$args['style']

is used without checking that it exists in several methods - end_el, end_lvl, ping, comment, html5_comment, start_lvl.

[SergeyBiryukov]

Hi there, thanks for the ticket!

It looks like the Walker_Comment class assumes that all the default arguments of wp_list_comments() would always be available, which may not necessarily be a correct assumption, so checking if they exist seems like a good idea.

To help move the ticket forward, could you share the steps to reproduce the issue on a clean install?

I added default values to each methods from Walker_Comment using $args to prevent using values without being sure they were initialized.

Trac ticket: https://core.trac.wordpress.org/ticket/56539