plugin-templates.php

<?php

// Template Logic
function twt_trailer_archive_template($original_template)
{
    // Set our post type
    $post_type = 'trailer';

    // Set the expected path for a override template within the site theme
    $file = trailingslashit(get_template_directory()) . "archive-$post_type.php";

    $plugin_directory = WP_PLUGIN_DIR . '/' . str_replace(basename(__FILE__), "", plugin_basename(__FILE__));

    // Check if we are on the archive page for our template
    if (is_post_type_archive($post_type)) {

        // Check if there is an override template within our theme
        if (file_exists($file)) {

            // if override file is found in activate theme then render our archive page using that theme
            return trailingslashit(get_template_directory()) . "archive-$post_type.php";
        } else {

            // if override file is not found then use the template from within our plugin
            return $plugin_directory . "templates/archive-$post_type.php";
        }
        // Check if we on a single page within our post type
    } elseif (is_singular($post_type)) {

        // Check if there is an override template within our theme
        if (file_exists(get_template_directory_uri() . "/single-$post_type.php")) {

            // if override file is found in activate theme then render our archive page using that theme
            return get_template_directory_uri() . "/single-$post_type.php";
        } else {
            // if override file is not found then use the template from within our plugin
            return plugin_dir_path(__DIR__) . "templates/single-$post_type.php";
        }
    }

    return $original_template;
}
add_action('template_include', 'twt_trailer_archive_template');