We have been migrating from the legacy gRPC generator to the newer one. You can tell which is which by looking at the BUILD.bazel file - any API using the legacy generator has a go_proto_library rule with compilers = ["@io_bazel_rules_go//proto:go_grpc"]; any API using the new generator has a go_grpc_library.

Sample migration commit

The support in the Go container is somewhat hacky (see the Dockerfile and look for protoc-gen-go-v1). We would like to remove this.

This depends on completing the migration to the new plugin for all google-cloud-go libraries, and the plan for go-genproto.