Protovalidate is the semantic validation library for Protobuf. It provides standard annotations to validate common rules on messages and fields, as well as the ability to use CEL to write custom rules. It's the next generation of protoc-gen-validate.

With Protovalidate, you can annotate your Protobuf messages with both standard and custom validation rules:

syntax = "proto3";
package acme.user.v1;
import "buf/validate/validate.proto";
message User {
  string id = 1 [(buf.validate.field).string.uuid = true];
  uint32 age = 2 [(buf.validate.field).uint32.lte = 150]; // We can only hope.
  string email = 3 [(buf.validate.field).string.email = true];
  string first_name = 4 [(buf.validate.field).string.max_len = 64];
  string last_name = 5 [(buf.validate.field).string.max_len = 64];
  option (buf.validate.message).cel = {
    id: "first_name_requires_last_name"
    message: "last_name must be present if first_name is present"
    expression: "!has(this.first_name) || has(this.last_name)"
  };
}

Once you've added protovalidate-python to your project, validation is idiomatic Python:

try:
    protovalidate.validate(message)
except protovalidate.ValidationError as e:
    # Handle failure.

To install the package, use pip:

pip install protovalidate

Comprehensive documentation for Protovalidate is available in Buf's documentation library.

Highlights for Python developers include:

• The developer quickstart
• A comprehensive RPC quickstart for Python and gRPC
• A migration guide for protoc-gen-validate users

Protovalidate isn't just for Python! You might be interested in sibling repositories for other languages:

• protovalidate-go (Go)
• protovalidate-java (Java)
• protovalidate-cc (C++)
• protovalidate-es (TypeScript and JavaScript)

Additionally, protovalidate's core repository provides:

• Protovalidate's Protobuf API
• Conformance testing utilities for acceptance testing of protovalidate implementations

We genuinely appreciate any help! If you'd like to contribute, check out these resources:

• Contributing Guidelines: Guidelines to make your contribution process straightforward and meaningful
• Conformance testing utilities: Utilities providing acceptance testing of protovalidate implementations

Offered under the Apache 2 license.