OneOf, AllOf, AnyOf Oh my! How to define union types in OpenAPI

The blog post provides a comprehensive guide to using the keywords oneOf, allOf, and anyOf in OpenAPI 3.X documents, which are based on JSON Schema and crucial for defining complex and flexible data structures within APIs. It explains that oneOf is used to specify scenarios where a property can have multiple possible data structures but only one is valid at a time, functioning similarly to union types in programming. allOf is used for combining multiple schemas into one, akin to intersection types, but can lead to illogical schemas if not handled carefully. anyOf is discussed as the most problematic due to its potential to create a combinatorial explosion of types, leading to unintended behavior in code generation; thus, it is recommended to be avoided unless absolutely necessary. The post also addresses common pitfalls and best practices, such as not using oneOf to denote nullable objects, and highlights the importance of understanding these distinctions to prevent downstream issues in SDK generation.