rust-protobuf: protoc-gen-rust does not follow common file placement conventions

Instead of outputting *.rs files to the “conventional” (per cpp, go, and python) directories – relative to the source proto files – the generated files are placed relative to the command invocation site.

When I run the following example command:

protoc --rust_out . ./first/second/example.proto

Instead of

./first/second/example.rs

We see

./example.rs

A more complete example with several generators:

> protoc --rust_out . ./first/second/example.proto
> protoc --cpp_out . ./first/second/example.proto
> protoc --go_out . ./first/second/example.proto
> protoc --python_out . ./first/second/example.proto
> protoc --java_out . ./first/second/example.proto
> tree
├── example.rs                             # Rust
├── first
│   └── second
│       ├── example_pb2.py                 # Python
│       ├── example.pb.cc                  # Cpp
│       ├── example.pb.go                  # Go
│       ├── example.pb.h                   # Cpp
│       └── example.proto                  # Proto
└── org
    └── pubref
        └── rules_protobuf
            └── examples
                └── CommonProto.java       # Java

It appears that only we and the Java rules break from “convention”.

I understand this change would likely break many existing users, so I’d understand if this change was rejected for that reason. Example short change diff

EDIT:

To clarify, the primary reason this is an issue for me (and hasn’t been for anyone else yet presumably) is because I’m using this protoc extension with bazel instead of cargo+build.rs file, specifically the rules_protobuf “library”. That library has an expectation built in that generated source files are placed in a directory structure adjacent to the underlying proto files. It seems that assumption holds for all protoc-gen-* except us and java.