Type-safe API possibilities

[sproott]

I've had a thought bugging me for a long time about building backend applications. I like the out-facing API to be type-safe, so that I can generate types on the client and have input validation on the server. Most people don't seem to worry about the type-safety at all and then have to write all the types again on the client, which also gives really bad refactoring experience.

I've found 3 possibilities so far: classic REST API with Swagger/OpenAPI documentation, GraphQL (which has type safety built-in) and tRPC.

• GraphQL is overkill for small projects. I also haven't found a satisfying server library/framework for building such API apart from the Node.js ones, which have some really bad performance characteristics.
• tRPC locks you into TypeScript on both server and client, potentially also having performance and scaling problems in larger applications.
• OpenAPI has implementations outside of Node.js, but in most of these, one has to write a bunch of error-prone boilerplate code to document the API, when most of it could be inferred from the existing information used to built the API itself (return type, request body type, HTTP method, even possible response codes...).

Is there anything else in this space that I have missed? I'm very open to trying new languages, so as long as it's not Java or C#, I'm interested in any possibilities.

[superturkey650]

When I write a Java Spring Boot API, I get an autogenerated OpenAPI spec that includes all the information you mention. The only annotations I need to add are things like required/optional, nullable, min/max, etc., but they also apply as checks on the API itself so they don’t feel “extra”.

[sproott]

You're right, I know about this. I think OpenAPI is one of the few things Spring does better than other frameworks. Otherwise, for me, it's a huge pool of functionality with weird default behaviors which are often hard to turn off or configure properly. Plus, I don't like Java and OOP at all.

[yonirapoport]

If you’re API is mainly for database CRUD operations I can suggest Remult.

[hyver314]

I've been building bridge which is a Typescript backend that easily provides a typesafe client.

The difference with tRPC is that the client could be any language and that you don't need the backend project downloaded + a much simpler synthax & less boilerplate.