prefer-mypy-performance-milestone

Detects mypy versions below known performance milestones in the 1.x series and suggests incremental upgrades.

What it detects

• pyproject.toml, requirements.txt, setup.cfg, setup.py, poetry.lock, or similar files pinning mypy to a 1.x version below a known speed milestone:
  • below 1.13 → suggest 1.13
  • below 1.15 → suggest 1.15
  • 1.18.0 or earlier → suggest 1.18.1

The major 2.x upgrade path is handled separately: consider-mypy-2-upgrade (1.x → 2.0, with a breaking-change note) and prefer-mypy-2-performance-milestone (2.x → 2.x), because mypy 2.0 is a breaking major release.

Why it matters

Each milestone release includes measurable type-checking speed improvements. Upgrading incrementally reduces risk while still delivering faster CI runs.

Suggested action

Bump mypy to the next milestone version, run the type-checker, and fix any new errors before targeting the next milestone.

Measurement

Compare mypy runtime before and after the upgrade.