Multiple required fields in WooCommerce - Enhance last year's code to make multiple WooCommerce product fields required. https://www.damiencarbery.com/2019/09/multiple-required-fields-in-woocommerce/

multiple-required-product-fields.php

<?php
/*
Plugin Name: Multiple Required fields (WooCommerce)
Plugin URI: https://www.damiencarbery.com/2019/09/multiple-required-fields-in-woocommerce/
Description: Enhance last year's code to make multiple WooCommerce product fields required.
Author: Damien Carbery
Author URI: http://www.damiencarbery.com
Version: 0.2
WC tested up to: 5.2.2
*/


add_action( 'admin_head', 'dcwd_require_weight_field' );
function dcwd_require_weight_field() {
	$screen         = get_current_screen();
	$screen_id      = $screen ? $screen->id : ''; 
	if ( $screen_id == 'product' ) {
?>
<script>
jQuery(document).ready(function($){
	required_fields_data = [
		[ 'Weight', '#_weight',        'Shipping', '.shipping_tab > a' ],
		[ 'Length', '#product_length', 'Shipping', '.shipping_tab > a' ],
		[ 'Width',  '#product_width',  'Shipping', '.shipping_tab > a' ],
		[ 'Height', '#product_height', 'Shipping', '.shipping_tab > a' ],
	];
	num_required_fields = required_fields_data.length;
	
	// Set the fields as required.
	for ( i = 0; i < num_required_fields; i++ ) {
		$( required_fields_data[ i ][ 1 ] ).prop('required',true);
	}

	// Verify that each required field has a non-zero value before allowing save.
	$( '#publish' ).on( 'click', function() {
		error_message = '';
		target_field = null;
		target_tab = null;
		for ( i = 0; i < num_required_fields; i++ ) {
			value = $.trim($( required_fields_data[ i ][ 1 ] ).val());
			if ( value == '' || value == 0  ) {
			error_message += required_fields_data[ i ][ 0 ] + " must be set in the "+ required_fields_data[ i ][ 2 ] +" tab.\n";
			target_field = required_fields_data[ i ][ 1 ];
			target_tab = required_fields_data[ i ][ 3 ];
			}
		}

		if ( error_message != '' ) {
			alert( error_message );
			
			$( target_tab ).click();  // Click on appropriate tab.
			$( target_field ).focus();  // Focus on the appropriate field.
			return false;
		}
	});
});
</script>
<?php
	}
}