prost-protovalidate

Runtime validation for Protocol Buffer messages using buf.validate rules, built for prost and prost-reflect.

Dynamically inspects prost-reflect message descriptors, compiles buf.validate constraint annotations (including CEL expressions), and evaluates them against concrete message instances.

Quick Start

[dependencies]
prost = "0.14"
prost-protovalidate = "0.1"

Annotate your .proto files with buf.validate rules:

syntax = "proto3";

import "buf/validate/validate.proto";

message CreateUserRequest {
  string name = 1 [(buf.validate.field).string.min_len = 1];
  int32 age = 2 [(buf.validate.field).int32.gte = 18];
}

Validate in Rust:

use prost_protovalidate::validate;

let request = CreateUserRequest {
    name: "Alice".to_string(),
    age: 25,
};

match validate(&request) {
    Ok(()) => println!("Validation passed!"),
    Err(e) => println!("Validation failed: {e}"),
}

For repeated validations, construct a Validator once to cache compiled rules:

use prost_protovalidate::Validator;

let validator = Validator::new();
validator.validate(&request)?;

Features

• Dynamic field inspection via prost-reflect descriptors — no static code generation needed for validators.
• CEL evaluation — compiles and evaluates Common Expression Language expressions for cross-field and complex constraints.
• Aggregated violations — collects all constraint failures instead of short-circuiting on the first error.
• Evaluation caching — Validator caches compiled AST/CEL rules, avoiding re-parsing on every call.

Compatibility

License

MIT OR Apache-2.0