ADR-040: Ruff for formatting and linting

Category: development Provenance: human

Decision

Use Ruff for both code formatting and linting. Ruff replaces multiple tools (Black, isort, Flake8, etc.) with a single fast tool.

Rationale

Ruff is 10-100x faster than legacy Python linters. Single tool replaces Black (formatting), isort (imports), Flake8 (linting), pyupgrade, etc. Reduces dependencies and configuration complexity. Written in Rust for speed. Same team makes ty type checker - good ecosystem integration. Pre-commit hooks run faster with Ruff.

Agent Instructions

Run 'ruff format' for code formatting. Run 'ruff check --fix' for linting. Configure Ruff in pyproject.toml. Use 'make format' and 'make lint' targets. Never introduce Black, isort, Flake8, or other legacy linters. Ruff handles all Python code quality checks.

Rejected Alternatives

Black + isort + Flake8

Slow, multiple tools to configure and maintain. Ruff is drop-in replacement that's much faster.

Pylint

Very slow, overly verbose. Ruff covers same checks with better performance.