An error will occur if you name your protobuf service "Result"

[stevenhansel]

Bug Report

Version

tonic 0.8
tonic-build 0.8

Platform

Darwin june.local 21.6.0 Darwin Kernel Version 21.6.0: Wed Aug 10 14:28:35 PDT 2022; root:xnu-8020.141.5~2/RELEASE_ARM64_T8101 arm64

Description

I found out an unique bug, I happened to name my proto service as "Result" because it's supposed to stream the result of a service. Here is my proto definition:

result.proto

syntax = "proto3";

import "google/protobuf/any.proto";
import "google/protobuf/empty.proto";

option go_package = "github.com/stevenhansel/binus-logbook/scraper/internal/grpc/proto/result";

package result;

service Result {
  rpc Listen(google.protobuf.Empty) returns (stream Reply) {}
}

message Reply {
  int32 step = 1;
  string name = 2;
  google.protobuf.Any data = 3;
}

Then when I run cargo build where inside in the build.rs looks like:

build.rs

fn main() {
    let protos: &'static [&str] = &[
        "../proto/helloworld.proto",
        "../proto/scraper.proto",
        "../proto/result.proto",
    ];

    for proto in protos {
        tonic_build::compile_protos(proto)
            .unwrap_or_else(|e| panic!("Failed to compile protos {:?}", e));
    }
    tauri_build::build()
}

It will show this error:

error[E0782]: trait objects must include the `dyn` keyword
   --> /Users/june/binus-logbook/src-tauri/target/debug/build/binus-logbook-69ad9dfa394bbbc0/out/result.rs:110:24
    |
110 |                 Item = Result<super::Reply, tonic::Status>,
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
help: add `dyn` keyword before this trait
    |
110 -                 Item = Result<super::Reply, tonic::Status>,
110 +                 Item = dyn Result<super::Reply, tonic::Status>,
    |

error[E0107]: this trait takes 0 generic arguments but 2 generic arguments were supplied
   --> /Users/june/binus-logbook/src-tauri/target/debug/build/binus-logbook-69ad9dfa394bbbc0/out/result.rs:110:24
    |
110 |                 Item = Result<super::Reply, tonic::Status>,
    |                        ^^^^^^----------------------------- help: remove these generics
    |                        |
    |                        expected 0 generic arguments
    |
note: trait defined here, with 0 generic parameters
   --> /Users/june/binus-logbook/src-tauri/target/debug/build/binus-logbook-69ad9dfa394bbbc0/out/result.rs:107:15
    |
107 |     pub trait Result: Send + Sync + 'static {
    |               ^^^^^^

error[E0191]: the value of the associated type `ListenStream` (from trait `result_server::Result`) must be specified
   --> /Users/june/binus-logbook/src-tauri/target/debug/build/binus-logbook-69ad9dfa394bbbc0/out/result.rs:110:24
    |
109 | /         type ListenStream: futures_core::Stream<
110 | |                 Item = Result<super::Reply, tonic::Status>,
    | |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: specify the associ

For me the fix was to rename the protobuf service in result.proto to another name.

result.proto

syntax = "proto3";

import "google/protobuf/any.proto";
import "google/protobuf/empty.proto";

option go_package = "github.com/stevenhansel/binus-logbook/scraper/internal/grpc/proto/result";

package result;

service ResultListener {
  rpc Listen(google.protobuf.Empty) returns (stream Reply) {}
}

message Reply {
  int32 step = 1;
  string name = 2;
  google.protobuf.Any data = 3;
}

I'm reporting this bug because it works just fine when I compile the protobuf with protoc for the Golang side.

[LucioFranco]

Yeah, i think this is something that is hard to fix due to Result being imported in the prelude. I would consider changing the name as it may just be incompatible with Rust.

[davidpdrsn]

I think if the generated code used a fully qualified path like ::std::result::Result then it should work.

[stevenhansel]

I think if the generated code used a fully qualified path like ::std::result::Result then it should work.

Great idea, I think I can open up a PR in the weekend if we're going with this way