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Comment by usrusr | Hacker News Reader

Feels like cheating, next to the yaml of openapi anything will look good. And that's all while I'm still considering openapi one of the best things that have happened.

But I've also been kind of holding my breath for typescript making it's breakthrough as a schema language. More specifically its surprisingly big non-imperative, non-functional subset, obviously. And at first glance this seems to be exactly this, "what if we removed javascript from typescript so that only typing for JSON remains and added some endpoint metadata description to make it a viable successor to openapi and wsdl.

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> next to the yaml of openapi anything will look good.

Challenge accepted!

https://github.com/bufbuild/protovalidate/blob/main/examples...

it doesn't look worse than OpenAPI's yaml to me

it's fairly concise, the method and the request/response types are well separated and readable

the only thing I could argue with is mixing validation and type defs, as it looks like one of these things that quickly evolve over time and you end up duplicating both in the schema and the business logic

TypeScript type system is very advanced. It won't be possible to generate corresponding bindings for all popular languages, while keeping them idiomatic. I'd prefer API language to be very simple and straightforward.

Many things that can't be expressed in a given type system can still be expressed quite nicely in code generated for the domain data. You might experience some name elements getting forcibly moved from the types universe into accessor method names. This is state representation (hopefully!), not the CORBA-era's pipe dream of magically remoting arbitrary objects across space and languages.

If for some reason your problem does involve tapping the depth of typescript type expressivity (the elaborate rule systems expressed in maplibre style JSON come to mind?), you'd better have the closest approximation you can get on the other end of the line.

OpenAPI's 'type system' is surprisingly advanced also, supporting explicitly discriminated unions and other things like that, which doesn't model well into all other languages.

Yep and that comes from JSON Schema: https://json-schema.org/

I believe recent versions of OpenAPI are "compatible" with JSON Schema (at least they "wanted to be" last I checked as I was implementing some schema converters).

Even TypeScript is not enough to represent all of JSON Schema! But it gets close (perhaps if you remove validation rules and stuff like that it's a full match).

But even something like Java can represent most of it pretty well, specially since sealed interfaces were added. I know because I've done it :).

So what happens if a server in another language uses that feature? You don't want to be able to represent that?

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