Proc macro example broken: Expecting something like Result<Foo, Err>

[SuperFluffy]

Compiling (a reduced version of) the jsonrpsee_proc_macros example is currently broken:

❯ cargo check
    Checking jsonrpeesee_derive_example v0.1.0 (/home/janis/dev/scratchpad/jsonrpeesee_derive_example)
error: Expecting something like 'Result<Foo, Err>' here, but got no generic args (eg no '<Foo,Err>').
 --> src/lib.rs:6:67
  |
6 |     async fn async_method(&self, param_a: u8, param_b: String) -> u16;
  |                                                                   ^^^

error: Expecting something like 'Result<Foo, Err>' here, but got no generic args (eg no '<Foo,Err>').
 --> src/lib.rs:8:30
  |
8 |     fn sync_method(&self) -> String;
  |                              ^^^^^^

error: could not compile `jsonrpeesee_derive_example` due to 2 previous errors

The reduced example (with cargo add jsonrpsee --features client,macros):

use jsonrpsee::proc_macros::rpc;

#[rpc(client, namespace = "foo")]
pub trait Rpc {
    #[method(name = "foo")]
    async fn async_method(&self, param_a: u8, param_b: String) -> u16;
    #[method(name = "bar")]
    fn sync_method(&self) -> String;
}

From a quick look at git-blame this PR introduced the change enforcing Result: #977

[niklasad1]

Hey @SuperFluffy

Which jsonrpsee version are you using? This example does only work on v0.18

[SuperFluffy]

@niklasad1 0.18.2. I ran cargo add jsonrpsee 5 minutes ago.

[package]
name = "jsonrpeesee_derive_example"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
jsonrpsee = { version = "0.18.2", features = ["client", "macros"] }

[niklasad1]

Ah, yeah you are running into #1067

For now you have to change the API to:

#[rpc(client, namespace = "foo")]
pub trait Rpc {
    #[method(name = "foo")]
    async fn async_method(&self, param_a: u8, param_b: String) -> Result<u16, Error>;
    #[method(name = "bar")]
    fn sync_method(&self) -> Result<String, Error>;
}

[niklasad1]

Closing this duplicate to #1067