[rbtying]

another former contributor to pb-jelly, though no longer at Dropbox.

protoc plugins have an interesting bootstrapping problem as well: the protoc-gen-$LANG interface requires the ability to ser/de protobuf messages that describe the proto file's AST. If your build system builds almost everything from scratch, including the protoc plugin, this means that you need to have a variant of your protoc plugin linked to a working proto implementation...

That's not to say this is impossible or even difficult, but at the time that I last looked at it (more than a year ago at this point), it made it fairly unpalatable to move the codegen from Python to Rust.