prefer newer "tomllib" over "tomli" backport (#14486)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

lib/ts_utils/metadata.py

@@ -8,6 +8,7 @@ from __future__ import annotations
 import datetime
 import functools
 import re
+import sys
 import urllib.parse
 from collections.abc import Mapping
 from dataclasses import dataclass
@@ -15,7 +16,11 @@ from pathlib import Path
 from typing import Annotated, Any, Final, NamedTuple, final
 from typing_extensions import TypeGuard
 
-import tomli
+if sys.version_info >= (3, 11):
+    import tomllib
+else:
+    import tomli as tomllib
+
 import tomlkit
 from packaging.requirements import Requirement
 from packaging.specifiers import Specifier
@@ -52,7 +57,7 @@ def _is_nested_dict(obj: object) -> TypeGuard[dict[str, dict[str, Any]]]:
 @functools.cache
 def get_oldest_supported_python() -> str:
     with PYPROJECT_PATH.open("rb") as config:
-        val = tomli.load(config)["tool"]["typeshed"]["oldest_supported_python"]
+        val = tomllib.load(config)["tool"]["typeshed"]["oldest_supported_python"]
     assert type(val) is str
     return val
 
@@ -92,7 +97,7 @@ class StubtestSettings:
 def read_stubtest_settings(distribution: str) -> StubtestSettings:
     """Return an object describing the stubtest settings for a single stubs distribution."""
     with metadata_path(distribution).open("rb") as f:
-        data: dict[str, object] = tomli.load(f).get("tool", {}).get("stubtest", {})
+        data: dict[str, object] = tomllib.load(f).get("tool", {}).get("stubtest", {})
 
     skip: object = data.get("skip", False)
     apt_dependencies: object = data.get("apt_dependencies", [])

lib/ts_utils/mypy.py

@@ -1,10 +1,14 @@
 from __future__ import annotations
 
+import sys
 from collections.abc import Generator, Iterable
 from contextlib import contextmanager
 from typing import Any, NamedTuple
 
-import tomli
+if sys.version_info >= (3, 11):
+    import tomllib
+else:
+    import tomli as tomllib
 
 from ts_utils.metadata import StubtestSettings, metadata_path
 from ts_utils.utils import NamedTemporaryFile, TemporaryFileWrapper
@@ -26,7 +30,7 @@ class MypyDistConf(NamedTuple):
 
 def mypy_configuration_from_distribution(distribution: str) -> list[MypyDistConf]:
     with metadata_path(distribution).open("rb") as f:
-        data = tomli.load(f)
+        data = tomllib.load(f)
 
     # TODO: This could be added to ts_utils.metadata
     mypy_tests_conf: dict[str, dict[str, Any]] = data.get("mypy-tests", {})