🔧 build(type): replace mypy with pyrefly

docs/changelog/1168.misc.rst

@@ -0,0 +1 @@
+Use ``pyrefly`` for project type checking and require 100% package type coverage - by :user:`gaborbernat`.

docs/development/contributing.rst

@@ -89,9 +89,8 @@ build follows modern Python code style conventions enforced by `ruff <https://do
 a pull request, run the linter to ensure your code meets the project's style guidelines. The ruff configuration is
 defined in the pyproject.toml file and includes both formatting and linting rules.
 
-The project also uses type annotations throughout the codebase. All new code should include appropriate type hints, and
-changes to existing code should preserve or improve type annotations. Use `pyright
-<https://microsoft.github.io/pyright/>`_ for type checking to verify your type annotations are correct.
+The project uses type annotations throughout the codebase. Add type hints to new code and preserve or improve existing
+annotations. The ``type`` tox environment runs `Pyrefly <https://pyrefly.org/>`_ and requires full package coverage.
 
 ***************
  Documentation

pyproject.toml

@@ -108,6 +108,7 @@ test = [
   { include-group = "extra" },
 ]
 typing = [
+  "colorama",
   "importlib-metadata >= 5.1",
   "tomli",
   "typing-extensions >= 4.0.0",
@@ -116,8 +117,8 @@ typing = [
   { include-group = "test-core" },
   { include-group = "extra" },
 ]
-mypy = [
-  "mypy ~= 2.3.0",
+pyrefly = [
+  "pyrefly >= 1.2",
   { include-group = "typing" },
 ]
 release = [
@@ -130,7 +131,7 @@ release = [
 dev = [
   "flit-core",
   { include-group = "test" },
-  { include-group = "mypy" },
+  { include-group = "pyrefly" },
 ]
 
 [tool.flit.sdist]
@@ -191,38 +192,19 @@ filterwarnings = [
   "ignore:os.path.commonprefix:DeprecationWarning" # https://github.com/pypa/pyproject-hooks/pull/222
 ]
 
-[tool.mypy]
-files = ["src", "tests", "tasks", "docs"]
-exclude = ["tests/packages"]
-python_version = "3.10"
-native_parser = true
-strict = true
-disallow_any_explicit = true
-disallow_any_decorated = true
-disallow_any_unimported = true
-disallow_untyped_globals = true
-disallow_redefinition = true
-warn_unused_configs = true
-warn_unreachable = true
-enable_error_code = [
-  "deprecated",
-  "exhaustive-match",
-  "ignore-without-code",
-  "mutable-override",
-  "possibly-undefined",
-  "redundant-expr",
-  "redundant-self",
-  "truthy-bool",
-  "truthy-iterable",
-  "unimported-reveal",
-  "unused-awaitable",
-]
-
-[[tool.mypy.overrides]]
-module = [
-  "virtualenv", # Optional dependency
-]
-ignore_missing_imports = true
+[tool.pyrefly]
+project-includes = ["src", "tests", "tasks", "docs"]
+project-excludes = ["**/tests/packages*"]
+search-path = ["src", "tests"]
+python-version = "3.10"
+preset = "all"
+
+[tool.pyrefly.errors]
+# `@override` needs typing_extensions before 3.12; build takes no runtime deps for typing
+missing-override-decorator = false
+# These style rules reject intentional truthiness checks and side-effect calls throughout the project.
+implicit-bool = false
+unused-call-result = false
 
 [tool.ruff]
 exclude = [

src/build/_builder.py

@@ -269,10 +269,15 @@ def get_requires_for_build(
         """
         _ctx.log(f'Getting build dependencies for {distribution}...', kind=('step',))
         hook_name = f'get_requires_for_build_{distribution}'
-        get_requires = getattr(self._hook, hook_name)
 
         with self._handle_backend(hook_name):
-            return set(get_requires(config_settings))
+            if distribution == 'editable':
+                requires = self._hook.get_requires_for_build_editable(config_settings)
+            elif distribution == 'sdist':
+                requires = self._hook.get_requires_for_build_sdist(config_settings)
+            else:
+                requires = self._hook.get_requires_for_build_wheel(config_settings)
+            return set(requires)
 
     def check_dependencies(
         self,

src/build/_ctx.py

@@ -21,17 +21,16 @@ class Logger(typing.Protocol):  # pragma: no cover
     def __call__(self, message: str, *, kind: tuple[str, ...] | None = None) -> None: ...
 
 
-_package_name = __spec__.parent
-_default_logger = logging.getLogger(_package_name)
+_default_logger = logging.getLogger(typing.cast('str', __spec__.parent))
 
 
 def _log_default(message: str, *, kind: tuple[str, ...] | None = None) -> None:  # noqa: ARG001
     # the log function that works in tests, real log function is set in __main__
     _default_logger.log(logging.INFO, message, stacklevel=2)
 
 
-LOGGER = contextvars.ContextVar('LOGGER', default=_log_default)
-VERBOSITY = contextvars.ContextVar('VERBOSITY', default=0)
+LOGGER = contextvars.ContextVar[Logger]('LOGGER', default=_log_default)
+VERBOSITY = contextvars.ContextVar[int]('VERBOSITY', default=0)
 
 
 def log_subprocess_error(error: subprocess.CalledProcessError) -> None:

src/build/_exceptions.py

@@ -24,7 +24,7 @@ def __init__(
         description: str | None = None,
     ) -> None:
         super().__init__()
-        self.exception = exception
+        self.exception: Exception = exception
         self._description = description
 
     def __str__(self) -> str:
@@ -49,7 +49,7 @@ class FailedProcessError(Exception):
 
     def __init__(self, exception: subprocess.CalledProcessError, description: str) -> None:
         super().__init__()
-        self.exception = exception
+        self.exception: subprocess.CalledProcessError = exception
         self._description = description
 
     def __str__(self) -> str:

src/build/_types.py

@@ -15,11 +15,13 @@
 
 # A decoded JSON value, as produced by ``json.load``. Uses the covariant ``Sequence``/``Mapping``
 # so concrete literals (e.g. ``str | list[str]``) are also assignable to it.
-JSONValue = str | int | float | bool | None | collections.abc.Sequence['JSONValue'] | collections.abc.Mapping[str, 'JSONValue']
+JSONValue: typing.TypeAlias = (
+    str | int | float | bool | collections.abc.Sequence['JSONValue'] | collections.abc.Mapping[str, 'JSONValue'] | None
+)
 
 # A value as produced by ``tomllib`` when parsing ``pyproject.toml``. Uses the covariant
 # ``Sequence``/``Mapping`` so concrete literals (e.g. ``dict[str, list[str]]``) are assignable.
-TOMLValue = (
+TOMLValue: typing.TypeAlias = (
     str
     | int
     | float

src/build/env.py

@@ -62,7 +62,7 @@ class _DistArgs(typing.TypedDict, total=False):
 
 Installer = typing.Literal['pip', 'uv']
 
-INSTALLERS = typing.get_args(Installer)
+INSTALLERS: tuple[Installer, ...] = typing.get_args(Installer)
 
 
 class IsolatedEnv(typing.Protocol):
@@ -107,6 +107,9 @@ class DefaultIsolatedEnv(IsolatedEnv):
     Isolated environment which supports several different underlying implementations.
     """
 
+    _env_backend: _EnvBackend
+    _path: str
+
     def __init__(
         self,
         *,
@@ -142,8 +145,6 @@ def __enter__(self) -> Self:
             path = os.path.realpath(path)
             self._path = path
 
-            self._env_backend: _EnvBackend
-
             # uv is opt-in only.
             if self.installer == 'uv':
                 self._env_backend = _UvBackend()
@@ -437,6 +438,9 @@ def display_name(self) -> str:
 
 
 class _UvBackend(_EnvBackend):
+    _env_path: str
+    _uv_bin: str
+
     def create(self, path: str) -> None:
         import venv
 

tasks/release.py

@@ -4,6 +4,7 @@
 
 from pathlib import Path
 from subprocess import call, check_call
+from typing import cast
 
 from git import Commit, Remote, Repo, TagReference
 from packaging.version import Version
@@ -39,7 +40,7 @@ def main(version_str: str, *, push: bool) -> None:
 def resolve_version(version_str: str, repo: Repo) -> Version:
     if version_str not in {'auto', 'major', 'minor', 'patch'}:
         return Version(version_str)
-    parts = [int(x) for x in repo.git.describe('--tags', '--abbrev=0').lstrip('v').split('.')[:3]]
+    parts = [int(part) for part in cast('str', repo.git.describe('--tags', '--abbrev=0')).lstrip('v').split('.')[:3]]
     match detect_bump() if version_str == 'auto' else version_str:
         case 'major':
             parts = [parts[0] + 1, 0, 0]

tests/conftest.py

@@ -15,7 +15,7 @@
 from collections.abc import Callable, Generator
 from functools import partial, update_wrapper
 from pathlib import Path
-from typing import Protocol
+from typing import Protocol, cast
 
 import pytest
 
@@ -53,7 +53,7 @@ def pytest_collection_modifyitems(config: pytest.Config, items: list[pytest.Item
         elif config.getoption('--only-integration'):  # pragma: no cover
             item.add_marker(skip_other)
     # run integration tests after unit tests
-    items.sort(key=lambda i: 1 if is_integration(i) else 0)
+    items.sort(key=is_integration)
 
 
 def _xfail_isolated_strict(item: pytest.Item, *, is_integration_file: bool) -> bool:
@@ -123,7 +123,7 @@ def is_setuptools(package_path: Path) -> bool:
     pyproject = package_path / 'pyproject.toml'
     try:
         with pyproject.open('rb') as f:
-            pp = tomllib.load(f)
+            pp = cast(dict[str, dict[str, str]], tomllib.load(f))
     except (FileNotFoundError, ValueError):
         return True
     return 'setuptools' in pp.get('build-system', {}).get('build-backend', 'setuptools')

tests/integration_sources.py

@@ -13,6 +13,7 @@
 import os
 import shutil
 import time
+import typing
 import urllib.request
 
 from pathlib import Path
@@ -44,7 +45,7 @@ def download_archive(name: str) -> tuple[Path, str]:
     for attempt in range(1, ATTEMPTS + 1):
         try:
             with urllib.request.urlopen(url) as request, partial.open('wb') as file_handler:
-                shutil.copyfileobj(request, file_handler)
+                shutil.copyfileobj(typing.cast(http.client.HTTPResponse, request), file_handler)
         except NETWORK_ERRORS as exception:  # noqa: PERF203
             partial.unlink(missing_ok=True)
             if attempt == ATTEMPTS:

tests/test_env.py

@@ -43,7 +43,7 @@ def test_make_extra_environ_overrides_pythonpath() -> None:
 
 def test_installed_versions(mocker: pytest_mock.MockerFixture) -> None:
     env = build.env.DefaultIsolatedEnv()
-    env._env_backend = SimpleNamespace(purelib='/purelib')
+    mocker.patch.object(env, '_env_backend', SimpleNamespace(purelib='/purelib'), create=True)
     distributions = mocker.patch(
         'build._compat.importlib.metadata.distributions',
         return_value=[
@@ -567,7 +567,7 @@ def test_virtualenv_no_wheel_flag(
     backend = build.env._PipBackend()
     backend.create('/some/path')
 
-    call_args = cli_run.call_args[0][0]
+    call_args = typing.cast(list[str], cli_run.call_args.args[0])
     assert ('--no-wheel' in call_args) is has_no_wheel
 
 
@@ -581,7 +581,7 @@ def test_install_dependencies_with_outer_pip(
     with build.env.DefaultIsolatedEnv() as env:
         env.install(['some-package'])
 
-    cmd = run_subprocess.call_args_list[-1][0][0]
+    cmd = typing.cast(list[str], run_subprocess.call_args_list[-1].args[0])
     assert cmd[:4] == [sys.executable, '-m', 'pip', '--python']
 
 

tests/test_main.py

@@ -17,7 +17,7 @@
 import zipfile
 
 from collections.abc import Callable, Generator
-from typing import TYPE_CHECKING, Protocol, TypedDict
+from typing import TYPE_CHECKING, Protocol, TypedDict, cast
 
 import pytest
 import pytest_mock
@@ -59,6 +59,19 @@ class BuildKwargs(TypedDict):
     env_dir: str | None
 
 
+class ArtifactReport(TypedDict):
+    name: str
+    path: str
+    kind: str
+    size: int
+    hashes: dict[str, str]
+
+
+class BuildReport(TypedDict):
+    version: str
+    artifacts: list[ArtifactReport]
+
+
 def make_kwargs(
     *,
     distributions: list[str] | None = None,
@@ -300,7 +313,7 @@ def test_build_package_via_sdist_passes_config_settings_to_build(mocker: pytest_
     )
 
     assert built == ['demo-1.0.0.tar.gz', 'demo-1.0.0-py3-none-any.whl']
-    extractall = tar_open.return_value.__enter__.return_value.extractall
+    extractall = cast(unittest.mock.MagicMock, tar_open.return_value.__enter__.return_value.extractall)
     extractall.assert_called_once()
     assert extractall.call_args.args[0] == 'temp-sdist-dir'
     build_cmd.assert_has_calls(
@@ -818,7 +831,7 @@ def test_metadata_json_output(
     build.__main__.main([package_test_setuptools, '--metadata', '-n'])
 
     stdout = capsys.readouterr().out
-    metadata = json.loads(stdout)
+    metadata = cast(dict[str, str], json.loads(stdout))
     # Name normalised in old versions of setuptools.
     assert metadata['name'] in {'test_setuptools', 'test-setuptools'}
     assert metadata['version'] == '1.0.0'
@@ -916,7 +929,8 @@ def test_log_dependency_versions(mocker: pytest_mock.MockerFixture) -> None:
 
 def test_log_dependency_versions_none(mocker: pytest_mock.MockerFixture) -> None:
     env = mocker.create_autospec(build.env.DefaultIsolatedEnv, instance=True)
-    env.installed_versions.return_value = {}
+    installed: dict[str, str] = {}
+    env.installed_versions.return_value = installed
     log = mocker.patch('build.__main__._ctx.log')
 
     build.__main__._log_dependency_versions(env, set())
@@ -1370,7 +1384,7 @@ def test_report_written(
 
     build.__main__.main([str(tmp_path), '-o', str(outdir), '--report', str(report)])
 
-    payload = json.loads(report.read_text(encoding='utf-8'))
+    payload = cast(BuildReport, json.loads(report.read_text(encoding='utf-8')))
     assert payload['version'] == '1.0'
     assert [artifact['name'] for artifact in payload['artifacts']] == names
     for artifact, name in zip(payload['artifacts'], names, strict=True):