prost-validate

A protobuf library extending prost with validation support.

This is a rust implementation of protoc-gen-validate.

It uses the prost crate to generate the derive based validation code.

For a reflection based implementation see the prost-reflect-validate crate.

Usage

It must be used with prost generated code.

All validation rules are documented in the proto file or in the protoc-gen-validate documentation.

cargo add prost-validate --features derive
cargo add prost-validate-build --build

Proto definition

proto/message.proto:

syntax = "proto3";

package validate.example;

import "validate/validate.proto";

message ExampleMessage {
  string content = 1 [(validate.rules).string = {const: "Hello, world!"}];
}

Build script

build.rs:

fn main() -> Result<(), Box<dyn std::error::Error>> {
    prost_validate_build::Builder::new()
        .compile_protos(&["message.proto"], &["proto", "../prost-validate-types/proto"])?:
    Ok(())
}

Validation

Include the generated code

include!(concat!(env!("OUT_DIR"), "/validate.example.rs"));

Using the generated code

fn main() {
    use example_proto::ExampleMessage;
    use prost_validate::Validator;

    match ExampleMessage::default().validate() {
        Ok(_) => println!("Validation passed"),
        Err(e) => eprintln!("Validation failed: {}", e),
    }
    let msg = ExampleMessage {
        content: "Hello, world!".to_string(),
    };
    match msg.validate() {
        Ok(_) => println!("Validation passed"),
        Err(e) => eprintln!("Validation failed: {}", e),
    }
}

Output:

Validation failed: "validate.example.ExampleMessage.content": must be equal to "Hello, world!"

Validation passed