modernize-attrs

A codemod to modernize your attrs usage by:

• Converting @attr.s and @attrs.s decorators to @define
• Moving type hints from attr.ib(type=...) to Python type annotations
• Converting attr.ib() to attrs.field()
• Removing empty field() calls when no other arguments are present

Usage

You can run the codemod without installing by using uvx or pipx run:

uvx git+https://github.com/jonathanberthias/modernize-attrs src_dir_or_file

Behavior

The codemod will convert code like this:

import attr

@attr.s
class MyClass:
    x = attr.ib(type=int, converter=int)
    y = attr.ib(type=str, default="hello")

Into:

from attrs import define, field

@define
class MyClass:
    x: int = field(converter=int)
    y: str = "hello"

Why?

The old way of using attr.s and attr.ib is now considered outdated. The attrs library has introduced @define and field() to provide a more Pythonic way of defining classes with attributes, leveraging type hints for better clarity and tooling support.

In particular, only Mypy can understand the type= argument in attr.ib(), making it harder to use other type checkers or get pleasant IDE support.

Safety Features

• The codemod will skip any class that contains attr.ib() calls without type hints and print a warning
• Existing type annotations are preserved
• Other attr.ib() arguments (like default, validator, etc.) are preserved in the field() call

Requirements

• Python >= 3.11
• libcst >= 1.5.1

Development

To set up for development:

# Clone the repository
git clone https://github.com/jonathanberthias/modernize-attrs
cd modernize-attrs

# Create a virtual environment and install dependencies
uv sync

# Run tests
uv run pytest