pants-ty 0.1.3

A Pants check backend for the Astral ty Python type checker.

pants-ty-plugin

pants-ty-plugin adds a Pants check backend for Astral ty.

It is designed for Pants 2.31.x and currently supports Linux and macOS. The backend installs ty as an external binary, then runs it with:

• a resolve-backed Python environment for third-party dependencies
• Pants source roots as --extra-search-path entries for first-party imports

That means ty can resolve imports that Pants already knows about.

Features

• pants check --only=ty ...
• skip_ty = true on Python targets
• ty.toml discovery
• [tool.ty] discovery from pyproject.toml
• resolve-aware --python
• source-root-aware --extra-search-path

Install

Option 1: install from PyPI through Pants

The recommended installation path is to use the published package from PyPI:

• PyPI: https://pypi.org/project/pants-ty/

Add the plugin to your repo's Pants config:

[GLOBAL]
plugins = ["pants-ty==0.1.3"]
backend_packages = [
  "pants.backend.python",
  "pants_ty",
]

Pants installs published plugins separately from your code resolves. Do not add pants-ty to a resolve, lockfile, or python_requirement.

Then add your ty.toml or [tool.ty] config and run:

pants help ty
pants check --only=ty ::

Option 2: vendor the plugin into a private repo

Copy only the Python package files from pants-plugins/pants_ty/ into your repo's pants-plugins/pants_ty/ directory:

• __init__.py
• register.py
• rules.py
• skip_field.py
• subsystem.py

Do not copy this plugin repo's development-only files:

• pants-plugins/BUILD
• pants-plugins/pants_ty/BUILD
• pants-plugins/lock.txt
• tests/
• this repo's pants.toml, pyproject.toml, or GitHub workflow files

Those files are only for developing and releasing pants-ty-plugin itself. A consuming repo should use its own resolves, lockfiles, and test setup.

Then configure:

[GLOBAL]
pants_version = "2.31.0"
backend_packages = [
  "pants.backend.python",
  "pants_ty",
]
pythonpath = ["%(buildroot)s/pants-plugins"]

If you accidentally copy the dev BUILD files too, you may see an error like:

UnrecognizedResolveNamesError: ... resolve ... pants-plugins

That means your consuming repo picked up this repo's internal development resolve. Remove the copied BUILD files and keep only the plugin Python modules.

Configure

Ty's own configuration must live in either:

• ty.toml
• pyproject.toml under [tool.ty]

Do not put [tool.ty] in pants.toml. Pants options go under [ty].

Example:

[tool.ty]
exclude = [".pants.d", "dist"]

Or in a dedicated ty.toml:

exclude = [".pants.d", "dist"]

Pants exposes the plugin options under [ty]:

[ty]
args = ["--output-format=concise"]
config_discovery = true

If your ty.toml lives somewhere else in the repo, point Pants at it explicitly:

[ty]
config = "config/python/ty.toml"

Overriding the Ty binary version

You do not need a new pants-ty release for every new ty release.

From a checkout of this repo, generate a ready-to-paste config block using the repo helper script:

./scripts/generate_known_versions.py 0.0.28

The script is the source of truth for known_versions values. Do not hand-edit hashes/sizes or pull them via other endpoints when preparing an update.

That prints:

[ty]
version = "0.0.28"
known_versions = [
  "0.0.28|linux_arm64|<sha256>|<size>",
  "0.0.28|linux_x86_64|<sha256>|<size>",
  "0.0.28|macos_arm64|<sha256>|<size>",
  "0.0.28|macos_x86_64|<sha256>|<size>",
]

Paste that block into the consuming repo's pants.toml.

Useful options:

./scripts/generate_known_versions.py 0.0.28 --platform macos_arm64 --platform linux_x86_64
./scripts/generate_known_versions.py 0.0.28 --entries-only

Release checklist shortcut:

./scripts/generate_known_versions.py <ty_version> > /tmp/ty-version.toml
cat /tmp/ty-version.toml

Each known_versions entry is version|platform|sha256|length. By default the script uses Astral's official GitHub release archives.

You only need to do this when you want to upgrade the downloaded ty binary without changing the plugin code. If a new ty release requires backend changes, then release a new pants-ty version.

Run pants help-advanced ty to see the full option shape, including url_template and url_platform_mapping.

Useful commands:

pants help ty
pants check --only=ty ::
pants check --only=ty path/to/pkg::

To skip a target:

python_sources(
  name="lib",
  skip_ty=True,
)

Setup

This repo expects mise and pants to already be installed:

• mise: https://mise.jdx.dev/installing-mise.html
• pants: https://www.pantsbuild.org/dev/docs/getting-started/installing-pants

The mise tasks use the installed Pants launcher directly, while mise manages the repo-local Python version used for packaging and helper scripts.

Development

This repo uses mise to install local development tools and provide task entrypoints for linting, testing, and releases.

mise install
mise run lint
mise run test
mise run check
mise run verify

The repository-managed tools currently include:

• python 3.11.14

mise run test passes PANTS_LAUNCHER=$(command -v pants) into the Pants-managed test process so the integration tests can invoke the same installed Pants launcher inside the test sandbox.

If you prefer to run the underlying commands directly, the task mapping is:

pants lint ::
pants "--test-extra-env-vars=['PANTS_LAUNCHER=$(command -v pants)']" test ::
pants check ::

To build a distributable wheel and sdist:

python -m build

Automated releases

After you configure PyPI trusted publishing for this repository, you can cut a release with:

mise install
mise run release 0.1.3

The release task wraps scripts/release.sh and uses the repo-managed python tooling from mise plus your installed pants launcher. The script will:

• require a clean main branch
• run pants lint ::, pants test ::, and pants check ::
• update the version in pyproject.toml
• update pants-plugins/pants_ty/__init__.py
• create a release commit
• create an annotated tag like v0.1.3
• push main
• push the tag

Useful flags:

mise run release-dry-run 0.1.3
mise run release -- --skip-checks 0.1.3

Repository layout

• pants-plugins/pants_ty: plugin source
• .mise/tasks: local development and release task wrappers
• mise.toml: repo-managed tool versions
• scripts/generate_known_versions.py: helper to generate [ty].known_versions overrides
• tests/pants_ty: unit and integration tests
• pants.toml: local development config
• pants.ci.toml: CI-specific Pants settings

Notes

• The Pants plugin API is not stable across minor versions. This repo currently targets Pants 2.31.x.
• The backend only resolves imports that Pants already knows through source roots and target resolves.