Introduce preflight filter to wp_delete_attachment().

[peterwilsoncc]

Introducing pre_delete_attachment to be friends with pre_delete_post would be helpful for large sites.

The signature would be identical:

apply_filters( 'pre_delete_attachment', bool|null $delete, WP_Post $post, bool $force_delete )

[joemcgill]

@peterwilsoncc is the goal here just to avoid having to check the post type of the post getting passed to the already included filter, or is there some other benefit? Alternatively, should we consider a more robust pre_delete_post_{$post_type} filter rather than special casing attachments?

If you could shed more light on the use case you see here, that would be helpful.

[peterwilsoncc]

@joemcgill

The intent is to make preflighting available for deleting attachments, at the moment it is unavailable due to the order of operation in wp_delete_post().

wp_delete_post() checks the post type and calls wp_delete_attachment() prior to calling the preflight hook:

<?php
// From wp_delete_post():

if ( 'attachment' === $post->post_type ) {
        return wp_delete_attachment( $postid, $force_delete );
}

/**
 * Filters whether a post deletion should take place.
 *
 * @since 4.4.0
 *
 * @param bool|null $delete       Whether to go forward with deletion.
 * @param WP_Post   $post         Post object.
 * @param bool      $force_delete Whether to bypass the Trash.
 */
$check = apply_filters( 'pre_delete_post', null, $post, $force_delete );
if ( null !== $check ) {
        return $check;
}

In 49597.diff​:

• introduce preflight hook
• For consistency with pre_delete_post and pre_trash_post, I've added the function below any relevant post type and status checking.

I've left the milestone as awaiting review to allow the media component team to consider.

[joemcgill]

@peterwilsoncc Ah, I missed that special treatment of attachments came before the preflight filter. Yes, this change makes perfect sense to me, given the state of things and also extends the preflight to any code calling wp_delete_attachment() directly. +1 from me.

[peterwilsoncc]

In 47448:

Media: Introduce preflight filter to wp_delete_attachment().

Introduces the filter pre_delete_attachment to allow developers to prevent or modify the deletion of attachments. This improves consistency with wp_delete_post() and wp_trash_post().

Props joemcgill, peterwilsoncc.
Fixes #49597.