seraphic

A synchronous, lightweight crate for creating your own JSON RPC 2.0 protocol.

WARNING: This is very early in development and is subject to significant change.

What is seraphic?

seraphic provides a straightforward way of defining your very own JSON RPC 2.0 based protocol messages using Rust macros.

A quick refresher on JSON RPC

Json rpc messages are structured as follows:

#[derive(Debug, Clone, Deserialize, Serialize, PartialEq)]
pub struct Request {
    pub jsonrpc: String,
    pub method: String,
    pub params: serde_json::Value,
    pub id: String,
}

#[derive(Debug, Clone, Deserialize, Serialize, PartialEq)]
pub struct Response {
    pub jsonrpc: String,
    pub result: Option<serde_json::Value>,
    pub error: Option<Error>,
    pub id: String,
}

#[derive(Debug, Clone, Deserialize, Serialize, PartialEq)]
pub struct Error {
    pub code: ErrorCode,
    pub message: String,
    pub data: Option<serde_json::Value>,
}

Manually creating these structs as JSON is easy enough, but organizing all the methods, requests and responses can quickly get hectic. seraphic offers a quick an easy way to define all of these!

Getting started

RpcNamespace

A trait for defining how the methods of your RPC protocol are separated

#[derive(RpcNamespace, Clone, Copy, PartialEq, Eq)]
#[namespace(separator=":")]
enum MyNamespace {
    Foo,
    Bar,
    Baz
}

The variants of the namespace enum define the method namespaces of your protocol. They are simply the variants' names in lowercase; so the above code will define your methods to have the namespaces "foo", "bar" and "baz", with methods appearing after a ':'.

If the separator argument isn't passed it defaults to '_'.

RpcRequest & RpcResponse

traits for defining the requests/responses that are used by your protocol

#[derive(RpcRequest, Clone, Deserialize, Serialize, Debug)]
#[rpc_request(namespace = "MyNamespace:foo")]
struct SomeFooRequest {
    field1: String,
    field2: u32,
    field3: serde_json::Value,
}

Each method in your namespace maps to a single request you've defined. Method names are defined by the whatever the name of your request is before the word "Request". So, the above struct's corresponding method would be "foo:someFoo". The syntax for mapping a request to a namespace is: <Namespace struct name>:<namespace variant>

NOTE:

Any struct you want to derive RpcRequest on MUST have a name ending with the word "Request" and all of it's fields MUST be types that implement serde::Serialize and serde::Deserialize

Each RpcRequest should have a corresponding RpcResponse struct. This can be done in two ways:

• Make sure another struct with the same prefix but with the word "Response" instead of "Request" is in scope

  #[derive(Debug, Clone, Serialize, Deserialize)]
  struct SomeFooResponse {}

• pass a response argument in the rpc_request proc macro attribute

  #[derive(RpcRequest, Clone, Deserialize, Serialize, Debug)]
  #[rpc_request(namespace = "MyNamespace:foo", response="SomeResponse")]
  struct SomeFooRequest {
      ...
  }
  #[derive(Debug, Clone, Serialize, Deserialize)]
  struct SomeResponse {}
  
  // If some response isn't the response to some other `RpcRequest` already
  impl RpcResponse for SomeResponse {
      // you could make this whatever you want, but the RpcRequest macro simply makes the IDENTITY the name of the struct in lowercase
      const IDENTITY: &str = "someresponse";
  }

Keep in mind:

• Both RpcRequest and RpcResponse structs MUST implement serde::Serialize, serde::Deserialize, Clone and Debug
• NEITHER RpcRequest or RpcResponse structs can be unit structs, they must have a body, even if they have no fields (which is unlikely)
• multiple RpcRequests can have the same corresponding RpcResponse
• If a response argument is passed in the rpc_request macros, the macro assumes the struct already implements RpcResponse, if not, the proc macros assumes the corresponding Response struct does not implement RpcResponse and will implement it for you.

RequestWrapper and ResponseWrapper

simply enums that include all of the RpcRequest and RpcResponse structs included in your protocol.

#[derive(Debug, Clone, ResponseWrapper, PartialEq)]
enum MyResponse {
  Some(SomeFooResponse)
}
#[derive(Debug, Clone, RequestWrapper, PartialEq)]
enum MyRequest {
  Some(SomeFooRequest)
}

These structs need only to implement Debug

Message<Rq,Rs>

The main type you will interact with for passing your messages.Rq is a RequestWrapper type and Rs is a ResponseWrapper type.

Referring to the tests might be helpful