This talk is an introduction to Cadl, a new, next-generation programming language for defining APIs. Developers use its simple core semantics and rich templating and extension mechanisms to represent APIs in any protocol and encapsulate common API shapes and patterns into reusable components. This description can be compiled to a variety of assets including standard OpenAPI3 or gRPC service descriptions, client or service code, documentation, database migrations, and other assets.
This talk will walk through building a web service which demonstrates many of these capabilities. Using the Cadl language combined with modern IDE features like code completions and refactorings, and leveraging the OpenAPI emitter from Cadl's standard library, we will develop a service description that can plug in to any OpenAPI3 code generation pipeline while requiring an order of magnitude less code. We will show how we to abstract out common parts of the service description to make subsequent API development and review faster and ensure consistency among all endpoints. We will demonstrate how to extend the API description to represent the same service in gRPC and represent other aspects of the service's implementation like the database ORM layer. Finally, we will cover Cadl's TypeScript-based extensibility model and library story which developers can use to build and share API patterns, custom language extensions, linters, emitters, and more.
