This library seems to be providing a framework and doesn’t include any interesting parsers. (There is no email address parser, despite the example.) It seems to allow for some composition of parsers, but the basic idea is a design pattern that’s simple enough that it doesn’t obviously require a framework.
So it seems like most of the value comes from standardizing on domain types like Username, Email, and so on. Using a framework doesn’t get you there, and it adds a dependency on the framework.
So it seems like most of the value comes from standardizing on domain types like Username, Email, and so on. Using a framework doesn’t get you there, and it adds a dependency on the framework.