How to build a Rust API with the builder pattern

Rust, unlike Python, lacks native support for optional and named arguments, but developers can effectively work around this using the builder pattern, which allows objects to be created with selected attributes while maintaining defaults for others. The builder pattern in Rust involves creating a builder object that holds the values and constructs the desired object once all necessary fields are set. This approach is particularly useful for complex types with multiple dependencies. Rust distinguishes between owned and mutably referenced builders, with the former requiring chaining and the latter allowing reuse without consuming the builder. Builders can also utilize traits like Into and AsRef for flexible input handling and support default values to streamline object construction. Additionally, Rust allows tracking of set fields using type states, although the complexity of implementation may outweigh benefits unless order control or optimization is needed. Various crates are available to automate the generation of builders, providing options for different use cases and preferences. While builders add extra code and maintenance, they are invaluable for complex Rust types, offering compile-time and runtime validation, and are widely recognized in the developer community, making them a familiar and efficient solution.