False Positive on has_post_thumbnail

Question

Within the loop, for a post (of custom post type) which does not have a featured image:

1. has_post_thumbnail() (with or without specified $post->ID) is returning true, while
2. get_the_post_thumbnail(), also with our without the $post->ID returns an empty string.

The loop:

$args = array(
'post_type' => 'customs', 
'post_status' => 'publish',
'fields' => 'id',
'posts_per_page' => -1
);
$query = new WP_Query($args);
while ( $query->have_posts() ) : $query->the_post(); 
  has_post_thumbnail();
  the_title(); // as expected
  the_excerpt(); // as expected
endwhile;

The CPT is defined as follows:

    $name          = 'Custom';
    $singular_name = 'Custom';
    $slug          = 'custom';
    $menu_icon     = 'universal-access';

    // Declare args and apply filters
    $args = array(
        'labels' => array(
            'name' => $name,
            'singular_name' => $singular_name,
            'add_new' => __( 'Add New', 'total' ),
            'add_new_item' => __( 'Add New Item', 'total' ),
            'edit_item' => __( 'Edit Item', 'total' ),
            'new_item' => __( 'Add New Custom Item', 'total' ),
            'view_item' => __( 'View Item', 'total' ),
            'search_items' => __( 'Search Items', 'total' ),
            'not_found' => __( 'No Items Found', 'total' ),
            'not_found_in_trash' => __( 'No Items Found In Trash', 'total' )
        ),
        'public' => true,
        'supports' => array(
            'title',
            'editor',
            'excerpt',
            'thumbnail',
            // 'comments',
            'custom-fields',
            'revisions',
            'author',
            'page-attributes',
        ),
        'capability_type' => 'post',
        'rewrite' => array( 'slug' => $slug, 'with_front' => false ),
        'has_archive' => true,
        'menu_icon' => 'dashicons-'. $menu_icon,
        'menu_position' => 20,
    );

    // Register the post type
    register_post_type( 'customs', $args );

}

While I can get desired outcome with:

if (get_the_post_thumbnail() !== ''):
  // display the thumbnail
else:
  // some other option
endif;

I'm confident that's not the solution. Where else can I poke around for what's causing this unexpected and undesired result?

Answer 1

I have tested on my test site the exact code you have shared above but it is working fine for me without any issue.

It seems you are facing the issue as described on this page WordPress has_post_thumbnail() not working – How to fix the phantom featured image issue that you might encounter, especially if you’re working with migrated content, or for some reason your database has weirdness.

So instead of has_post_thumbnail() you can use code like following to check existence of thumbnail attached to post.

$img_url = wp_get_attachment_url( get_post_thumbnail_id() );

if  ( ! empty( $img_url ) ) {

 // Do what you want to do if featured image is set to post
}