This shows how the protobuf.js build tools and runtime library can be used to consume .proto files.
Note that the example requires some “userland” code to invoke the tools, since there is no “custom rule” to invoke them under Bazel. See defs.bzl for the sample code you will need.
Currently the example doesn't exercise the Service definitions in the proto, but we expect this is easily added. It would be a great community contribution.