Must-use Local Plugin WooCommerce

mu-plugin.php

<?php
/**
 * Must-use plugin
 *
 * @package taw
 */

add_action(
	'admin_head',
	function() {
		// force show the product type dropdown.
		?>
		<style>.product_data .type_box.hidden { display: block; }</style>
		<?php
	}
);

/**
 * Add "Empty Cart" button to cart page
 */
function mu_woocommerce_empty_cart_button() {
	echo '<a href="' . esc_url( add_query_arg( 'empty_cart', 'yes' ) ) . '" class="button btn btn-primary ml-2" title="' . esc_attr__( 'Empty Cart', 'woocommerce' ) . '">' . esc_html__( 'Empty Cart', 'woocommerce' ) . '</a>';
}
add_action( 'woocommerce_cart_actions', 'mu_woocommerce_empty_cart_button' );

/**
 * Empty WC cart
 */
function mu_woocommerce_empty_cart_action() {
	if ( isset( $_GET['empty_cart'] ) ) {
		WC()->cart->empty_cart();
		$referer = remove_query_arg( 'empty_cart' );
		wp_safe_redirect( $referer );
	}
}
add_action( 'wp_loaded', 'mu_woocommerce_empty_cart_action', 20 );


/**
 * Dump var wrapped in pre tags for pretty print in HTML
 *
 * @param  mixed $var Any variable.
 */
function pre_dump( $var ) {
	echo '<pre>';
	var_dump( $var );
	echo '</pre>';
}

/**
 * Replace local images with remote.
 *
 * @param  array $image Image.
 * @return array $image Replaced image.
 */
function mu_use_remote_images( $image ) {
	if ( ! empty( $image[0] ) && defined( 'REMOTE_IMAGE_URL' ) ) {

		// only replace the url if the image doesn't exist locally.
		$relative_path = str_replace( site_url() . '/', '', $image[0] );
		if ( ! file_exists( ABSPATH . $relative_path ) ) {
			$image[0] = str_replace( site_url(), rtrim( REMOTE_IMAGE_URL, '/' ), $image[0] );
		}
	}

	return $image;
}

if ( defined( 'REMOTE_IMAGE_URL' ) ) {
	add_filter( 'wp_get_attachment_image_src', 'mu_use_remote_images' );

	// disable srcsets since they're not being replaced with remote.
	add_filter( 'wp_calculate_image_srcset', '__return_false' );
}

/**
 * Add a button to the nav menu that adds the first simple product found to the cart.
 *
 * @usage add_filter( 'nav_menu_item_args', 'mu_add_first_product_to_cart' );
 *
 * @see wp_nav_menu() For default args.
 * @param object $args Nav menu args.
 * @return object $args Updated args.
 */
function mu_add_first_product_to_cart( $args ) {
	if ( isset( $_GET['mu-add-to-cart'] ) ) {
		wp_safe_redirect( wc_get_checkout_url() );
	}
	$cart_is_empty = 0 >= WC()->cart->get_cart_contents_count();
	$query_args = array(
		'post_type'      => 'product',
		'posts_per_page' => 1,
		'tax_query'      => array(
			array(
				'taxonomy' => 'product_type',
				'field'    => 'slug',
				'terms'    => 'simple',
			),
		),
	);

	$loop = new WP_Query( $query_args );
	$link = '';
	while ( $loop->have_posts() ) :
		$loop->the_post();
		$params = $cart_is_empty ? site_url( '?mu-add-to-cart=true&add-to-cart=' . get_the_ID() ) : '?empty_cart=yes';
		$label  = $cart_is_empty ? 'Checkout' : 'Empty';
		$link  .= '<li class="menu-item nav-item"><a class="nav-link" href="' . $params . '">' . $label . '</li></a>';
	endwhile;
	wp_reset_postdata();
	$args->items_wrap = '<ul id="%1$s" class="%2$s">' . $link . '%3$s</ul>';
	return $args;
}