tonic: Client/Server /can be/ duplicated into their include files

There are a few different issues that I’ve found so far. First, take this set of proto files:

syntax = "proto3";

import "types.proto";

package helloworld;

service Greeting {
  rpc Hello (Message) returns (Response) {}
}

syntax = "proto3";

import "types.proto";

package helloworld;

service Farewell {
  rpc Goodbye (Message) returns (Response) {}
}

syntax = "proto3";

package helloworld;

message Message {
  string say = 1;
}

message Response {
  string say = 1;
}

And the following build.rs:

fn main() {
    tonic_build::compile_protos("proto/hello.proto").unwrap();
    tonic_build::compile_protos("proto/goodbye.proto").unwrap();
    println!("cargo:rerun-if-changed=proto/hello.proto");
    println!("cargo:rerun-if-changed=proto/goodbye.proto");
    println!("cargo:rerun-if-changed=proto/types.proto");

This fails to work because building goodbye.proto completely overwrites the output file generated for hello.proto.

Ok, maybe the Builder type is smarter, since you can provide a list of paths to multiple proto files? Let’s update build.rs:

fn main() {
    tonic_build::configure()
        .compile(&["proto/hello.proto", "proto/goodbye.proto"], &["proto"])
        .unwrap();
    println!("cargo:rerun-if-changed=proto/hello.proto");
    println!("cargo:rerun-if-changed=proto/goodbye.proto");
    println!("cargo:rerun-if-changed=proto/types.proto");
}

And this also fails because now the generated output has duplicate client and server modules for the two different services defined in the helloworld package.

I’m curious why it worked fine on tower-grpc as well though. It seems like it’s possible and this is just a regression in the rewrite.

Using tower-grpc with the same build file (gathers all proto files with services in to the array) doesn’t have the same issue

I hit this problem with a different repro case. Compiling two proto files with the same package name defining unique services will output Rust source code like:

// services for first proto file in package "foo"
pub mod client {}
pub mod server {}

// services for second proto file in package "foo"
pub mod client {}
pub mod server {}

Which then leads to errors:

error[E0428]: the name `client` is defined multiple times
error[E0428]: the name `server` is defined multiple times

I have to merge all proto files for the single package into one file to workaround this issue.