Metabox Actions Not Firing

[gin0115]

There is 2 parts to this issue.

• Race condition when checking if a metabox is active.
• Meta Box should be populated with the post type that registered it.

Race Condition solution

Meta_Box_Registrar::register( Meta_Box $meta_box )

$this->loader->action(
    'current_screen',
    function() use ( $meta_box ) {
        // If we have any hook calls, add them to the loader.
        if ( $this->is_active( $meta_box ) && ! empty( $meta_box->actions ) ) {
            foreach ( $meta_box->actions as $handle => $hook ) {
                add_action( (string) $handle, $hook['callback'], $hook['priority'], $hook['params'] );
            }
        }
    }
);

Auto populate the meta box with cpt used on.

Registerable_Middleware::process_post_type()

// Register meta boxes.
$meta_boxes = $post_type_registerable->meta_boxes( array() );

if ( ! empty( $meta_boxes ) ) {

    // Create the registrar
    $meta_box_registrar = $this->get_meta_box_registrar();

    // Register each meta box.
    foreach ( $meta_boxes as $meta_box ) {
        $meta_box->screen( $post_type_registerable->key );
        $meta_box_registrar->register( $meta_box );
    }
}