Custom Post Type Draft Preview Goes to 404

Question

I have created a custom post type within a custom plugin.

Here is my post type definition:

function hrd_record_custom_post_type() {

    $args = array(
        'description'         => __( 'hrdrecord', 'hrd_record' ), 
        'public'              => true, 
        'publicly_queryable'  => true, 
        'exclude_from_search' => false, 
        'show_in_nav_menus'   => true, 
        'show_ui'             => true, 
        'show_in_menu'        => true, 
        'show_in_admin_bar'   => true, 
        'menu_position'       => null, 
        'menu_icon'           => null, 
        'can_export'          => true, 
        'delete_with_user'    => false, 
        'hierarchical'        => false, 
        'has_archive'         => true, 
        'query_var'           => true, 
        'capability_type'     => 'hrdrecord', 
        'map_meta_cap'        => true, 
        'capabilities' => array(

            'edit_post'              => 'edit_hrdrecord',
            'read_post'              => 'read_hrdrecord',
            'delete_post'            => 'delete_hrdrecord',
            'create_posts'           => 'create_hrdrecords',
            'edit_posts'             => 'edit_hrdrecords',
            'edit_others_posts'      => 'edit_others_hrdrecords',
            'publish_posts'          => 'publish_hrdrecords',
            'read_private_posts'     => 'read_private_hrdrecords',
            'read'                   => 'read',
            'delete_posts'           => 'delete_hrdrecords',
            'delete_private_posts'   => 'delete_private_hrdrecords',
            'delete_published_posts' => 'delete_published_hrdrecords',
            'delete_others_posts'    => 'delete_others_hrdrecords',
            'edit_private_posts'     => 'edit_private_hrdrecords',
            'edit_published_posts'   => 'edit_published_hrdrecords'
        ),

        'rewrite' => array(
            'slug'       => 'hrdrecord', 
            'with_front' => false, 
            'pages'      => true, 
            'feeds'      => true, 
            'ep_mask'    => EP_PERMALINK, 
        ),


        'taxonomies' => array( 'location','sex','type-of-work','type-of-killing','previous-threat', 'gender-component', 'status-of-investigation','sector','sector-detail'),
        'supports' => array(
            'author',
            'thumbnail',
        ),

        'labels' => array(
            'name'               => __( 'HRD Record',                   'hrd_record' ),
            'singular_name'      => __( 'HRD Record',                    'hrd_record' ),
            'menu_name'          => __( 'HRD Record',                   'hrd_record' ),
            'name_admin_bar'     => __( 'HRD Record',                   'hrd_record' ),
            'add_new'            => __( 'Add New',                    'hrd_record' ),
            'add_new_item'       => __( 'Add New HRD Record',            'hrd_record' ),
            'edit_item'          => __( 'Edit HRD Record',               'hrd_record' ),
            'new_item'           => __( 'New HRD Record',                'hrd_record' ),
            'view_item'          => __( 'View HRD Record',               'hrd_record' ),
            'search_items'       => __( 'Search HRD Records',            'hrd_record' ),
            'not_found'          => __( 'No HRD Record found',          'hrd_record' ),
            'not_found_in_trash' => __( 'No HRD Record in trash',       'hrd_record' ),
            'all_items'          => __( 'All HRD Records',               'hrd_record' ),

            'archive_title'      => __( 'hrdrecord',                   'hrd_record' ),
        )
    );

    register_post_type(
        'hrdrecord', 
        $args      
    );


}
add_action( 'init', 'hrd_record_custom_post_type' );

The problem I am having is that when I have one of these post types in Draft and I click the Preview button (either from the All HRD Records listing or from the individual HRD Record edit screen) I am brought to a 404 Not Found page. But if the post is published, I have no problems Previewing Changes before updating or otherwise viewing the post type.

One thing that is also odd is that when I try to Preview from the listing, the URL has query parameters in the link of ?post_type=hrdrecord&p=999&preview=true But once this appears in the browser the &preview=true query variable disappears and even if I try to manually retype it, once I hit return, it is removed from the URL (only the ?post_type=hrdrecord&p=999 remain).

When I try the Preview button on the individual screen this string of variables is rewritten as ?post_type=hrdrecord&p=999&preview_id=999&preview_nonce=some set of numbers and letters but it still goes to a 404 not found page.

I have tried a number of things that I've found here and in other forums about similar problems but nothing is sorting it.

1. I have tried changing themes
2. I have tried removing parameters in the post type definition that are being set to their default values
3. I have reset the Permalinks a number of times (also my plugin has a flush_rewrite_rules(); in both the activation and deactivation hooks and I have deactivated and re-activated the plugin a couple of times)
4. I have changed the 'with_front' parameter in the 'rewrite' to true
5. I have disabled all other plugins

So I am now at a loss. I am assuming it is related to rewrites and some parameter in the custom post type definition but I don't know which one or how to get Wordpress to associate the preview query variables with the post type.

Any suggestions would be most appreciated.

Answer 1

I had a colleague take a look at the entire plugin code and he found a function I had written which was forcing the query to only show 'Published' posts. This was interfering with the preview as it was being treated as a front-end query. I was able to bypass it by adding the parameter !$query->is_preview() to my conditions and it is now sorted.