oapi-codegen is a suite of generators that converts OpenAPI 3 specifications into type-safe Go client libraries, server boilerplate, and data models. It provides tools for producing production-ready HTTP clients and server-side interfaces to ensure that Go implementations remain compliant with defined API contracts.
The tool supports server generation across various web frameworks and allows for extensive customization via template overrides, specification overlays, and custom type definition mappings. It handles complex API requirements through external reference resolution to organize code across multiple packages and specification overlay merging to modify definitions without altering the original source.
The project covers data modeling with specialized handling for nullable types to distinguish between missing fields and explicit null values. It also includes middleware for request validation to verify that incoming HTTP requests match the specification schemas.