zio-blocks-rpc: RPC type class for service trait introspection (derives RPC)

[987Nabil]

Summary

Add a zio-blocks-rpc module providing a derives RPC type class that captures service trait structure as a "pure data" representation — analogous to how derives Schema works for data types.

Design Direction (per @jdegoes)

trait MyService { ... } derives RPC

Then derive gRPC, JSON RPC, etc. from the "pure data" representation. ZIO Schema is used for input/output types.

Key Design Decisions

• Module: zio-blocks-rpc / package zio.blocks.rpc
• Type class: RPC[T] — runtime data structure capturing service operations (names, schemas, annotations, errors)
• Schema integration: Macro auto-summons Schema for all I/O types during derivation
• ZIO effect unwrapping: Methods must return ZIO[R, E, A] — macro extracts output type A and error type E
• Protocol derivation: RpcDeriver[Protocol[_]] trait (analogous to Schema's Deriver[TC[_]])
• Reference protocol: JSON-RPC 2.0 included as proof-of-concept
• Annotations: MetaAnnotation and ErrorAnnotation[E] for service/method-level metadata
• Scala version: Scala 3 only
• Platforms: JVM + JS (crossProject)

Inspiration

• bishabosha/ops-mirror (Apache-2.0) — compile-time trait method introspection
• ZIO Blocks Schema codec derivation pattern (Format/Deriver/Schema)

[jdegoes]

I really want to call this ZIO RPC, if this is what I think it is.

[987Nabil]

@jdegoes I think this is more a dependency for zio rpc. It is the analysis of the structure of a service, that can be used to impl the rpc or the annotation based endpoints we discussed for http

[ghostdogpr]

Isn't it this already? https://github.com/bishabosha/ops-mirror

[987Nabil]

@ghostdogpr yes, looks like it
@jdegoes what is your opinion on how to proceed with this?

[jdegoes]

@987Nabil I want this to be more ZIO Schema-ish:

trait MyService { ... } derives RPC

Then you can derive gRPC, JSON RPC, etc. from the "pure data" representation.

Obviously, Schema would be used for input / output types.