Referencing external protos like google/rpc/status.proto

Question

I'm wondering how to properly reference external proto files. Say I've got a .proto file which references standard protobuf types such as Timestamp:

syntax = "proto3";
package api;

import "google/protobuf/timestamp.proto";

message ServerTimeResponse {
  google.protobuf.Timestamp ts = 1;
}

Easy. Timestamp is automatically available when compiling.

Now I add an external type, say google.rpc.Status:

syntax = "proto3";
package api;

import "google/protobuf/timestamp.proto";
import "google/rpc/status.proto";

message ServerTimeResponse {
  google.protobuf.Timestamp ts = 1;
  google.rpc.Status status = 2;
}

Of course we have to tell protoc how to find this file where it is via -I/--proto_path.

My question is this: What is the best practice for actually referencing this file, in particular to make version control happy? There appears not to be a go mod equivalent for protobufs. I've seen it copied verbatim into projects (such as in grpc-gateway) or just referenced from the local filesystem.

Answer 1

I think you sort of answered your own question here. I've done both successfully: manually copied the necessary files in verbatim (from https://github.com/googleapis/googleapis/tree/master/google and https://github.com/protocolbuffers/protobuf/tree/master/src/google/protobuf), and referenced local copies of the files.

If you want to do this and make version control happy, you could add these two repositories as git submodules inside your repository. Just make sure to pass the right locations to protoc using -I. E.g.:

cd $PROJECT_DIR
mkdir third_party && cd third_party
git submodule add https://github.com/googleapis/googleapis/tree/master/google
cd $PROJECT_DIR
<git commit the change>
protoc -I third_party/google <the rest of your protoc command>

As for referencing local copies of the files, and making sure they're present before attempting to build, you may find that adding something like the following to your Makefile will help (this is in a Go build environment):

go get -u github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway
go get -u github.com/golang/protobuf/protoc-gen-go
grpc_gateway_path=$(go list -m -f '{{.Dir}}' github.com/grpc-ecosystem/grpc-gateway)
googleapis_path="$grpc_gateway_path/third_party/googleapis"
protoc -I $googleapis_path --go_out=. <list of input files>