protoc-gen-pydantic

protoc-gen-pydantic is a protoc plugin that automatically generates Pydantic model definitions from .proto files. This tool is designed to help developers seamlessly integrate protobuf-defined models with Pydantic, a powerful data validation and settings management library for Python.

Features

• Supports all standard proto3 field types.
• Handles nested messages and enums.
• Generates Pydantic models with type annotations and field descriptions.
• Supports oneof, optional, repeated, and map fields.
• Retains comments from .proto files as docstrings in the generated models.

Installation

You can download the binaries from GitHub Releases.

Build from Source

You first need to have Go installed. If you don't have Go installed, you can download it from the Go downloads page.

Clone the repository and build the plugin:

git clone https://github.com/ornew/protoc-gen-pydantic
cd protoc-gen-pydantic
go build -o protoc-gen-pydantic main.go

Usage

To generate Pydantic model definitions, use protoc with your .proto files specifying --pydantic_out:

protoc --plugin=protoc-gen-pydantic=./protoc-gen-pydantic \
       --pydantic_out=./gen \
       --proto_path=./proto_files \
       ./api/example.proto

If you use buf:

# buf.gen.yaml
version: v2
plugins:
  - local: protoc-gen-pydantic
    opt:
      - paths=source_relative
    out: gen
inputs:
  - directory: api

buf config init
buf generate

Example

Given a simple .proto file:

syntax = "proto3";

package example;

// User model representing the example.User message.
message User {
  string name = 1;
  int32 age = 2;
  repeated string emails = 3;
  bool is_active = 4;
}

Running protoc will generate a Pydantic model like this:

from enum import Enum as _Enum
from typing import Optional as _Optional

from pydantic import BaseModel as _BaseModel, Field as _Field

class User(_BaseModel):
    """
    User model representing the example.User message.
    """
    name: str = _Field(...)
    age: int = _Field(...)
    emails: list[str] = _Field(...)
    is_active: bool = _Field(...)

Options

option	description
preserving_proto_field_name	Use the proto field naming for the output field name. If false, it will be in caml-case according to protojson rules. Defaults to false.
auto_trim_enum_prefix	Automatically remove prefixes from enum fields. Defaults to true
use_integers_for_enums	Use integers for enum values instead of enum names. Defaults to false.
disable_field_description	Disable generating the field description. Defaults to false.
use_none_union_syntax_instead_of_optional	Use `T

auto_trim_enum_prefix

enum Status {
  STATUS_UNSPECIFIED = 0;
  STATUS_OK = 1;
  STATUS_ERROR = 2;
}

If auto_trim_enum_prefix is false:

class Status(str, _Enum):
    STATUS_UNSPECIFIED = "UNSPECIFIED"
    STATUS_OK = "OK"
    STATUS_ERROR = "ERROR"

If auto_trim_enum_prefix is true (default):

class Status(str, _Enum):
    UNSPECIFIED = "UNSPECIFIED"
    OK = "OK"
    ERROR = "ERROR"

use_integers_for_enums

If use_integers_for_enums is false:

class Status(str, _Enum):
    UNSPECIFIED = "UNSPECIFIED"
    OK = "OK"
    ERROR = "ERROR"

If use_integers_for_enums is true:

class Status(int, _Enum):
    UNSPECIFIED = 0
    OK = 1
    ERROR = 2

disable_field_description

If disable_field_description is true:

message User {
    // User name
    string name = 1;
}

class User(_BaseModel):
    # User name
    name: str = _Field(..., description="User name")

If disable_field_description is false:

class User(_BaseModel):
    # User name
    name: str = _Field(...)

use_none_union_syntax_instead_of_optional

If use_none_union_syntax_instead_of_optional is true: Optional[T] If use_none_union_syntax_instead_of_optional is false: T | None

Contributing

Contributions are welcome! Please open an issue or submit a pull request with your changes.

License

This project is licensed under the Apache License 2.0. See LICENSE for more details.

Contact

If you have any questions, feel free to reach out to the author:

• Name: Arata Furukawa
• Email: old.river.new@gmail.com