Remove Slug from Custom Post Type results in 404

Question

I am working on a plugin that creates lists. After creating a list, I wanted to remove the slug from the url

Post type:

$rewrite = [
        'slug'       => 'single-link',
        'with_front' => false,
        'pages'      => false,
        'feeds'      => false,
    ];
    $args    = [
        'label'               => esc_html__( 'Single Link', 'single-link' ),
        'labels'              => $labels,
        'supports'            => [ 'title' ],
        'hierarchical'        => false,
        'public'              => true,
        'show_ui'             => true,
        'show_in_menu'        => true,
        'menu_position'       => 15,
        'menu_icon'           => 'dashicons-admin-links',
        'show_in_admin_bar'   => false,
        'show_in_nav_menus'   => true,
        'can_export'          => true,
        'has_archive'         => false,
        'exclude_from_search' => true,
        'publicly_queryable'  => true,
        'rewrite'             => $rewrite,
        'capability_type'     => 'page',
        'show_in_rest'        => true,
    ];

    $args = apply_filters( 'single-link/post_type/args', $args );
    register_post_type( 'single-link', $args );

Remove the slug from the URL:

function remove_cpt_slug( $post_link, $post, $leavename ) {

if ( 'single-link' != $post->post_type || 'publish' != $post->post_status ) {
    return $post_link;
}

$post_link = str_replace( '/' . $post->post_type . '/', '/', $post_link );

return $post_link;
 }
add_filter( 'post_type_link', 'remove_cpt_slug', 10, 3 );


function change_slug_struct( $query ) {

if ( ! $query->is_main_query() || 2 != count( $query->query ) || ! isset( $query->query['page'] ) ) {
    return;
}

if ( ! empty( $query->query['name'] ) ) {
    $query->set( 'post_type', array( 'post', 'single-link', 'page' ) );
}
}
add_action( 'pre_get_posts', 'change_slug_struct' );

(this code is from here)

Now after hitting publish, the slug /single-link/ gets deleted, but we always get a 404 when visiting the page. Changing/re-Saving the permalinks did not help. What am I doing wrong?

Answer 1

The registering of the custom post type and the permalink modification is OK. The problem is with the WordPress rewrite rules that more than likely will match the "cleaned up" URL of your simple links to pages and it will set the pagename query var not name as your change_slug_struct() function assumed.

So change the function to this to account for all cases:

function change_slug_struct( $query ) {

    if ( ! $query->is_main_query() || 2 != count( $query->query ) || ! isset( $query->query['page'] ) ) {
        return;
    }

    if ( ! empty( $query->query['name'] ) ) {
        $query->set( 'post_type', array( 'post', 'single-link', 'page' ) );
    } elseif ( ! empty( $query->query['pagename'] ) && false === strpos( $query->query['pagename'], '/' ) ) {
        $query->set( 'post_type', array( 'post', 'single-link', 'page' ) );

        // We also need to set the name query var since redirect_guess_404_permalink() relies on it.
        $query->set( 'name', $query->query['pagename'] );
    }
}
add_action( 'pre_get_posts', 'change_slug_struct' );

Answer 2

You have to alter the perma structure. By default your custom post type's post will only be found wenether the url starts with the slug prefix. When changing the prefix you will have similar issues as when deleting it, have a look at this post.

To achieve removal of the post type slug prefix you should hook into single-link_rewrite_rules and iterate through those rules and remove the prefix there as well.

Note: changes in the perma structure may cause url conflicts.

Answer 3

For multiple Custom Post Types adjust like this

     $query->set( 'post_type', array( 'post', 'custom1', 'page' ) && array( 'post', 'custom2', 'page' ) );