Recently, I’ve been doing a lot of work with Tonic, a Rust implementation of
the gRPC protocol. Like many implementations of gRPC, Tonic generates code from
the protocol buffers definitions at build time using the tonic-build crate in a Cargo
build script, and by default puts them in the path referred to by OUT_DIR. This has
the unfortunate side effect that tooling such as IntelliJ Rust does
not see the generated code for the purposes of analysis and completion - something very
useful for the verbose generated protocol buffers code - unless you take some additional
steps.