Joining Errors

An order arrives with three problems: no customer name, an item with a quantity of 0, and an item with a negative price. A validator that returns at the first problem reports one of the three. The client fixes it, sends the order again, and receives the second problem. The client therefore needs three requests to learn what is wrong with one order.

A validator that checks every field needs one request, and the client learns all three problems at once. However, this validator has several errors to report, and a function has only one error result.