feat(rpc-types-trace): always serialize result if no error

[jsvisa]

Motivation

I'm checking with reth's trace results with erigon's, seems erigon will always return result:null if no error occurred:

And found the OG OpenEthereum's serialized logic as below:

https://github.com/openethereum/openethereum/blob/main/crates/rpc/src/v1/types/trace.rs#L532

  match self.result {
        Res::Call(ref call) => struc.serialize_field("result", call)?,
        Res::Create(ref create) => struc.serialize_field("result", create)?,
        Res::FailedCall(ref error) => struc.serialize_field("error", &error.to_string())?,
        Res::FailedCreate(ref error) => struc.serialize_field("error", &error.to_string())?,
        Res::None => struc.serialize_field("result", &None as &Option<u8>)?,
    }

Solution

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mattsse]

is this causing issues?

do you know when this can be null?

[jsvisa]

is this causing issues?

Not really, I'm comparing the trace results between reth and erigon, and then found this issue(see the diff image)

do you know when this can be null?

suicide's results were null

after thinking twice, I think we can keep the same format as erigon's, result always present, error omitted if none https://github.com/erigontech/erigon/blob/13b4b7768485736e54ff5ca3270ebeec5c023ba8/turbo/jsonrpc/trace_types.go#L62-L63

type ParityTrace struct {
...
	Error               string       `json:"error,omitempty"`
	Result              interface{}  `json:"result"`
...
}

@mattsse WDYT

[mattsse]

I see, then this makes sense