protoc-fetcher

protoc-fetcher downloads an official release of the protobuf compiler (protoc) and returns the path to it.

Usage

use std::env;
use std::path::Path;

// From within build.rs...
let protoc_version = "31.1";
let out_dir = env::var("OUT_DIR").unwrap();
let protoc_path = protoc_fetcher::protoc(protoc_version, Path::new(&out_dir));

The release archive matching the given version will be downloaded, and the protoc binary will be extracted into a subdirectory of out_dir. You can choose a version from the release page, for example "31.1". Don't prefix it with a "v".

out_dir can be anywhere you want, but if calling this function from a build script, you should probably use the OUT_DIR env var (which is set by Cargo automatically for build scripts).

A previously downloaded protoc binary of the correct version will be reused if already present in out_dir.

Tonic/Prost

If you are using tonic-build (or prost-build), you can instruct it to use the fetched protoc binary by setting the PROTOC env var.

use std::env;
use std::path::Path;

let out_dir = env::var("OUT_DIR").unwrap();
let path_to_my_protos = Path::new("a/b/c");
let protoc_path = protoc_fetcher::protoc("31.1", Path::new(&out_dir)).unwrap();
env::set_var("PROTOC", &protoc_path);
tonic_build::compile_protos(path_to_my_protos);