typsht

type checker agnostic parallel type checking tool. run multiple python type checkers (mypy, pyright, ty, pyre) in parallel on the same code.

inspired by tox, but specifically for type checkers. get comprehensive type checking coverage by running multiple type checkers simultaneously.

installation

quick start (no installation)

use uvx to run typsht without installing it:

# check inline code
uvx typsht 'def foo(x: int) -> str: return x'

# check a file
uvx typsht --file my_module.py

install to your project

uv add typsht

usage

check inline code:

# this will catch the type error across all checkers
typsht 'def foo(x: int) -> str: return x'

check a file:

typsht --file my_module.py

run specific type checkers:

typsht --file my_module.py --checkers mypy --checkers ty

show detailed output from each checker:

typsht --file my_module.py --verbose

project support

typsht automatically detects when checking files in a uv project (containing pyproject.toml or uv.lock) and runs type checkers using uv run --project, giving them access to your local development packages.

this is useful for library developers who want to verify type annotations work across multiple checkers:

# in a project with local packages installed in editable mode
uvx typsht --file repros/test_case.py --verbose

# type checkers will have access to your local package imports

inline code always runs in an isolated environment.

pytest plugin

typsht includes a pytest plugin for running type safety tests across multiple type checkers. the key feature is inline assertions that work identically across mypy, pyright, and ty.

inline assertions (checker-agnostic)

use # R: type for reveal_type assertions and # E: pattern for error assertions:

- case: reveal_type_works_across_checkers
  checkers: [mypy, pyright, ty]
  main: |
    x: list[str] = ["a", "b"]
    reveal_type(x)  # R: list[str]

- case: error_detected_across_checkers
  checkers: [mypy, pyright, ty]
  main: |
    def foo(x: int) -> str:
        return x  # E: return

the plugin normalizes type representations (builtins.int -> int, List -> list, Literal[42] -> int) so the same assertion works across all checkers.

legacy format (pytest-mypy-plugins compatible)

also supports the pytest-mypy-plugins format for migrating existing tests:

- case: mypy_specific_output
  main: |
    x: int = 42
    reveal_type(x)
  out: 'Revealed type is "builtins.int"'

- case: should_pass_check
  main: |
    def add(a: int, b: int) -> int:
        return a + b
  should_pass: true

run the tests:

pytest tests/typesafety/

programmatic assertions

for python tests, use the assertion helpers directly:

from typsht import assert_type_equals, assert_type_error, assert_no_errors, CheckerType

def test_reveal_type():
    assert_type_equals('''
        x: int = 1
        reveal_type(x)
    ''', line=2, expected_type="int", checkers=[CheckerType.MYPY, CheckerType.PYRIGHT, CheckerType.TY])

def test_catches_error():
    assert_type_error('''
        def foo(x: int) -> str:
            return x
    ''', error_pattern="return", checkers=[CheckerType.MYPY, CheckerType.PYRIGHT, CheckerType.TY])

def test_valid_code():
    assert_no_errors('''
        def add(a: int, b: int) -> int:
            return a + b
    ''', checkers=[CheckerType.MYPY, CheckerType.PYRIGHT, CheckerType.TY])

supported type checkers

by default, typsht runs:

• mypy - widely adopted static type checker
• pyright - fast static type checker from microsoft
• ty - experimental blazing-fast type checker

also available (requires project configuration):

• pyre - facebook's type checker (requires .pyre_configuration)

development

install dependencies:

uv sync

run tests:

uv run pytest

install pre-commit hooks:

uv run pre-commit install