Refactor Macros to Apply to Impl Blocks for Ergonomics (#43)

[BigFish2086]

This PR addresses Issue #43 by refactoring the restate-sdk-rust macros to apply directly to impl blocks instead of requiring separate trait definitions. The change improves ergonomics, eliminates the need for FooBar/FooBarImpl naming conventions, and aligns the SDK with more idiomatic Rust patterns.

Current Macros:

• #[service], #[object], and #[workflow] with support for optional attributes like
  vis = "pub" which is needed to control the visibility of the generated Serve and Client structs and
  name = "my_service" for overriding the service name.

• #[handler] to mark which of the methods are service handlers. It also supports optional attributes like
  name = "my_handler" to override the handler name and shared in case of having an Object or a Workflow to support concurrent use of the handler.

Example:

use restate_sdk::prelude::*;

pub struct Counter;

#[restate_sdk::object(vis = "pub")]
impl Counter {
    #[handler(name = "add_value")]
    async fn add(&self, _ctx: ObjectContext<'_>, val: u64) -> Result<u64, TerminalError> {
        unimplemented!()
    }
    #[handler(shared, name = "get_counter")]
    async fn get(&self, _ctx: SharedObjectContext<'_>,) -> Result<u64, TerminalError> {
        unimplemented!()
    }
}

[github-actions]

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[BigFish2086]

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[slinkydeveloper]

Do I understand correctly that the changes to the macro won't support both the impl block and the trait? Because I think we should support both impl block and trait.

The trait variant is perfect when you need to strongly separate in different modules of your project the "API" of the service (containing, among the others, the macro generated client) and the "IMPL" of the service (which perhaps you want it to live in a separate module).

[BigFish2086]

Hello, @slinkydeveloper,

I think I misunderstood the intent of this issue and removed trait support—will add it back.

Questions:

1. Is this proposed impl macro syntax (e.g., #[restate_sdk::service(name = "my_service")],
   #[handler(shared)], etc.) good as-is?
2. Should the trait variant use similar syntax?

Let me know.

[musjj]

Any progress here? The new macro looks so much more ergonomic.

[BigFish2086]

Hi @musjj,

Haven't progressed since due to questions on new/old syntax. Like the #[restate_sdk::object(vis = "pub")] visibility trick feels clunky—any better ideas?

[slinkydeveloper]

Any progress here? The new macro looks so much more ergonomic.

Hi, sorry but TBH I won't have much time for this PR any time soon, we've other priorities atm and before this PR I would like to complete #33 first.