tonic-build

Provides code generation for service stubs to use with tonic. For protobuf compilation via prost, use the tonic-prost-build crate.

Feature flags

cleanup-markdown: Enables cleaning up documentation from the generated code. Useful when documentation of the generated code fails cargo test --doc for example. The prost feature must be enabled to use this feature.
prost: Enables usage of prost generator (enabled by default).
transport: Enables generation of connect method using tonic::transport::Channel (enabled by default).

Features

Required dependencies

[dependencies]
tonic = "<tonic-version>"
prost = "<prost-version>"

[build-dependencies]
tonic-prost-build = "<tonic-version>"

Getting Started

For protobuf compilation, use tonic-prost-build in your build.rs file at the root of the binary/library.

You can rely on the defaults via

fn main() -> Result<(), Box<dyn std::error::Error>> {
    tonic_prost_build::compile_protos("proto/service.proto")?;
    Ok(())
}

Or configure the generated code deeper via

fn main() -> Result<(), Box<dyn std::error::Error>> {
   tonic_prost_build::configure()
        .build_server(false)
        .compile_protos(
            &["proto/helloworld/helloworld.proto"],
            &["proto/helloworld"],
        )?;
   Ok(())
}

For further details how to use the generated client/server, see the examples here or the Google APIs example below.

NixOS related hints

On NixOS, it is better to specify the location of PROTOC and PROTOC_INCLUDE explicitly.

$ export PROTOBUF_LOCATION=$(nix-env -q protobuf --out-path --no-name)
$ export PROTOC=$PROTOBUF_LOCATION/bin/protoc
$ export PROTOC_INCLUDE=$PROTOBUF_LOCATION/include
$ cargo build

The reason being that if prost_build::compile_protos fails to generate the resultant package, the failure is not obvious until the include!(concat!(env!("OUT_DIR"), "/resultant.rs")); fails with No such file or directory error.

Google APIs example

A good way to use Google API is probably using git submodules.

So suppose in our proto folder we do:

git submodule add https://github.com/googleapis/googleapis

git submodule update --remote

And a bunch of Google proto files in structure will be like this:

├── googleapis
│   └── google
│       ├── api
│       │   ├── annotations.proto
│       │   ├── client.proto
│       │   ├── field_behavior.proto
│       │   ├── http.proto
│       │   └── resource.proto
│       └── pubsub
│           └── v1
│               ├── pubsub.proto
│               └── schema.proto

Then we can generate Rust code via this setup in our build.rs:

fn main() -> Result<(), Box<dyn std::error::Error>> {
    tonic_prost_build::configure()
        .build_server(false)
        //.out_dir("src/google")  // you can change the generated code's location
        .compile_protos(
            &["proto/googleapis/google/pubsub/v1/pubsub.proto"],
            &["proto/googleapis"], // specify the root location to search proto dependencies
        )?;
    Ok(())
}

Then you can reference the generated Rust like this this in your code:

pub mod api {
    tonic::include_proto!("google.pubsub.v1");
}
use api::{publisher_client::PublisherClient, ListTopicsRequest};

Or if you want to save the generated code in your own code base, you can uncomment the line .out_dir(...) above, and in your lib file config a mod like this:

pub mod google {
    #[path = ""]
    pub mod pubsub {
        #[path = "google.pubsub.v1.rs"]
        pub mod v1;
    }
}