protoc-rs is a simple standalone command line tool for generating a usable Rust crate from Protobuf .proto files. It is not a Rust implementation of protoc but rather a supplement to it when a set of Protobuf definitions need to be compiled into multiple languages and Rust being one of them.

Requirements

The Cargo manifest file, Cargo.toml must exist (it will not be generated). It must depend on tonic and prost, e.g.

[dependencies]
tonic = "0"
prost = "0"

If the repository contains protobuf generated files for multiple languages, it is recommended to put the generated Rust files into a subdirectory called rust/ instead of the usual source path src/. That makes it clear that this directory contains the generated Rust code, while other subdirectories contain other language code (e.g. go/, cpp/, ...). To make this work and make the crate importable, the custom source code location must also be set in the Cargo.toml. For example:

[lib]
path = "rust/lib.rs"

The root library file is always the default name lib.rs.

Usage by example

1. Navigate to the crates root directory (e.g. where Cargo.toml is located).
2. Compile the .proto files. The command works similar to protoc. If they are located under proto/, the command would look like this:

   protoc-rs -I proto/ --out=rust/ proto/*.proto
   

   All compiled proto files must be passed to a single call of the command so the lib.rs file can be generated accordingly. Also, all source files must be put under one of the specified include paths.

Now, the rust/ directory contains a valid Rust module structure and the crate can be imported by other crates. You can validate the crate by running cargo check.