Crate prost_protovalidate 

Runtime validation for Protocol Buffer messages using buf.validate rules.

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

Quick start

For one-off validation, use the validate convenience function:

use prost_protovalidate::validate;
match validate(&msg) {
    Ok(()) => { /* message is valid */ }
    Err(e) => eprintln!("validation failed: {e}"),
}

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

use prost_protovalidate::Validator;
let validator = Validator::new();
validator.validate(&msg).expect("message should be valid");

Feature flags

Feature	Default	Description
cel	Yes	CEL expression evaluation and chrono time support. Disable for a lighter dependency footprint when only standard rules are used.
tonic	No	Adds tonic integration: a From<ValidationError> for tonic::Status impl and a ValidateRequest extension trait so gRPC handlers can call req.validate_inner()?.
tonic-types	No	Implies tonic. Attaches a google.rpc.BadRequest detail with one FieldViolation per Violation to validation-failure statuses.

Without the cel feature, any message or field annotated with CEL expressions (via both cel and legacy cel_expression, including buf.validate.predefined rules) will produce a CompilationError at validation time. Standard rules (range checks, string constraints, format validators, etc.) work without cel.

Error types

Type	When
ValidationError	One or more constraint violations detected
CompilationError	A CEL expression or constraint definition failed to parse
RuntimeError	An unexpected failure during evaluation

All three are unified under Error.

Re-exported types

The types module re-exports prost-protovalidate-types so consumers do not need to depend on it directly.

Re-exports

pub use prost_protovalidate_types as types;

pub use regex;

Modules

time

Time helpers shared between the runtime validator and code generated by prost-protovalidate-build.

tonic

Optional integration with tonic (gRPC).

validators

Format validators for well-known string constraints.

Structs

CompilationError

Returned when a validation rule cannot be compiled from its descriptor.

RuntimeError

Returned when runtime evaluation of dynamic rules fails.

ValidationError

Returned when one or more validation rules are violated.

Validator

Thread-safe validator for Protocol Buffer messages.

Violation

A single instance where a validation rule was not met.

Enums

Error

Top-level error type returned by validation.

ValidationOption

Options for configuring a single Validator::validate_with call.

ValidatorOption

Options for configuring the Validator at construction time.

Traits

Filter

Controls which fields/messages are validated.

Validate

Compile-time validation for Protocol Buffer messages with generated validators.

Functions

normalize_edition_descriptor_set

Normalize protobuf Edition 2023 descriptors to proto3 format for compatibility with prost-reflect 0.16 which does not support editions. Normalize a FileDescriptorSet so that any Edition 2023 files are rewritten as proto3. Returns the original bytes unchanged if no edition files are detected.

validate

Validate a message using a global Validator instance.