Improving Elixir Argument Validation with NimbleOptions

In dynamic languages like Elixir, argument validation often relies on idiomatic patterns like function guards and pattern matching. The NimbleOptions library, however, offers a robust solution by allowing developers to create detailed validation schemas for keyword arguments. Andrés Alejos uses NimbleOptions in his 'EXGBoost' library to handle a plethora of parameter validations that are known for being complex due to dependency on other parameters and require custom validations, overridable configuration defaults, and parameter transformations. By defining custom types and schemas, Alejos shows how NimbleOptions can streamline both validation logic and documentation. The library's composability is highlighted through its ability to keep definition schemas as keyword lists that can be easily combined or extended, giving developers powerful tools to manage configuration parameters in Elixir applications. Overall, the use of NimbleOptions not only aids in maintaining clear and maintainable code but also produces well-structured documentation that benefits both users and future contributors to the codebase.