Enable flake8-type-checking rule

docs/source/conf.py

@@ -24,6 +24,9 @@
 # For trio itself
 sys.path.insert(0, os.path.abspath("../.."))
 
+# Enable reloading with `typing.TYPE_CHECKING` being True
+os.environ["SPHINX_AUTODOC_RELOAD_MODULES"] = "1"
+
 # https://docs.readthedocs.io/en/stable/builds.html#build-environment
 if "READTHEDOCS" in os.environ:
     import glob
@@ -88,6 +91,8 @@ def autodoc_process_signature(
             # Strip the type from the union, make it look like = ...
             signature = signature.replace(" | type[trio._core._local._NoValue]", "")
             signature = signature.replace("<class 'trio._core._local._NoValue'>", "...")
+        # Don't specify PathLike[str] | PathLike[bytes], this is just for humans.
+        signature = signature.replace("StrOrBytesPath", "str | bytes | os.PathLike")
 
     return signature, return_annotation
 

docs/source/reference-io.rst

@@ -728,6 +728,8 @@ task and interact with it while it's running:
 
    .. automethod:: fileno
 
+.. autoclass:: trio._subprocess.StrOrBytesPath
+
 .. autoclass:: trio.Process()
 
    .. autoattribute:: returncode

docs/source/typevars.py

@@ -6,13 +6,16 @@
 
 import re
 from pathlib import Path
+from typing import TYPE_CHECKING
 
 import trio
-from sphinx.addnodes import Element, pending_xref
-from sphinx.application import Sphinx
-from sphinx.environment import BuildEnvironment
 from sphinx.errors import NoUri
 
+if TYPE_CHECKING:
+    from sphinx.addnodes import Element, pending_xref
+    from sphinx.application import Sphinx
+    from sphinx.environment import BuildEnvironment
+
 
 def identify_typevars(trio_folder: Path) -> None:
     """Record all typevars in trio."""

pyproject.toml

@@ -106,6 +106,7 @@ select = [
   "ASYNC",  # flake8-async
   "PYI",  # flake8-pyi
   "SIM",  # flake8-simplify
+  "TCH",  # flake8-type-checking
 ]
 extend-ignore = [
     'F403',  # undefined-local-with-import-star

trio/_channel.py

@@ -2,7 +2,6 @@
 
 from collections import OrderedDict, deque
 from math import inf
-from types import TracebackType
 from typing import (
     TYPE_CHECKING,
     Generic,
@@ -19,6 +18,8 @@
 from ._util import NoPublicConstructor, final, generic_function
 
 if TYPE_CHECKING:
+    from types import TracebackType
+
     from typing_extensions import Self
 
 

trio/_core/_asyncgens.py

@@ -4,7 +4,6 @@
 import sys
 import warnings
 import weakref
-from types import AsyncGeneratorType
 from typing import TYPE_CHECKING, NoReturn
 
 import attr
@@ -17,6 +16,7 @@
 ASYNCGEN_LOGGER = logging.getLogger("trio.async_generator_errors")
 
 if TYPE_CHECKING:
+    from types import AsyncGeneratorType
     from typing import Set
 
     _WEAK_ASYNC_GEN_SET = weakref.WeakSet[AsyncGeneratorType[object, NoReturn]]

trio/_core/_ki.py

@@ -3,8 +3,6 @@
 import inspect
 import signal
 import sys
-import types
-from collections.abc import Callable
 from functools import wraps
 from typing import TYPE_CHECKING, Final, Protocol, TypeVar
 
@@ -16,6 +14,9 @@
 RetT = TypeVar("RetT")
 
 if TYPE_CHECKING:
+    import types
+    from collections.abc import Callable
+
     from typing_extensions import ParamSpec, TypeGuard
 
     ArgsT = ParamSpec("ArgsT")

trio/_core/_multierror.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 import sys
-from collections.abc import Callable, Sequence
 from types import TracebackType
 from typing import TYPE_CHECKING, Any, ClassVar, cast, overload
 
@@ -13,6 +12,8 @@
     from exceptiongroup import BaseExceptionGroup, ExceptionGroup
 
 if TYPE_CHECKING:
+    from collections.abc import Callable, Sequence
+
     from typing_extensions import Self
 ################################################################
 # MultiError

trio/_core/_parking_lot.py

@@ -73,7 +73,6 @@
 
 import math
 from collections import OrderedDict
-from collections.abc import Iterator
 from typing import TYPE_CHECKING
 
 import attr
@@ -82,6 +81,8 @@
 from .._util import final
 
 if TYPE_CHECKING:
+    from collections.abc import Iterator
+
     from ._run import Task
 
 

trio/_core/_run.py

@@ -10,20 +10,11 @@
 import threading
 import warnings
 from collections import deque
-from collections.abc import (
-    Awaitable,
-    Callable,
-    Coroutine,
-    Generator,
-    Iterator,
-    Sequence,
-)
 from contextlib import AbstractAsyncContextManager, contextmanager, suppress
 from contextvars import copy_context
 from heapq import heapify, heappop, heappush
 from math import inf
 from time import perf_counter
-from types import TracebackType
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -62,11 +53,23 @@
 if sys.version_info < (3, 11):
     from exceptiongroup import BaseExceptionGroup
 
-from types import FrameType
 
 if TYPE_CHECKING:
     import contextvars
+    import types
+    from collections.abc import (
+        Awaitable,
+        Callable,
+        Coroutine,
+        Generator,
+        Iterator,
+        Sequence,
+    )
+    from types import TracebackType
 
+    # for some strange reason Sphinx works with outcome.Outcome, but not Outcome, in
+    # start_guest_run. Same with types.FrameType in iter_await_frames
+    import outcome
     from typing_extensions import Self
 
 DEADLINE_HEAP_MIN_PRUNE_THRESHOLD: Final = 1000
@@ -1314,7 +1317,7 @@ def child_nurseries(self) -> list[Nursery]:
         """
         return list(self._child_nurseries)
 
-    def iter_await_frames(self) -> Iterator[tuple[FrameType, int]]:
+    def iter_await_frames(self) -> Iterator[tuple[types.FrameType, int]]:
         """Iterates recursively over the coroutine-like objects this
         task is waiting on, yielding the frame and line number at each
         frame.
@@ -2257,7 +2260,7 @@ def start_guest_run(
     async_fn: Callable[..., Awaitable[RetT]],
     *args: object,
     run_sync_soon_threadsafe: Callable[[Callable[[], object]], object],
-    done_callback: Callable[[Outcome[RetT]], object],
+    done_callback: Callable[[outcome.Outcome[RetT]], object],
     run_sync_soon_not_threadsafe: Callable[[Callable[[], object]], object]
     | None = None,
     host_uses_signal_set_wakeup_fd: bool = False,

trio/_core/_tests/test_asyncgen.py

@@ -3,15 +3,17 @@
 import contextlib
 import sys
 import weakref
-from collections.abc import AsyncGenerator
 from math import inf
-from typing import NoReturn
+from typing import TYPE_CHECKING, NoReturn
 
 import pytest
 
 from ... import _core
 from .tutil import buggy_pypy_asyncgens, gc_collect_harder, restore_unraisablehook
 
+if TYPE_CHECKING:
+    from collections.abc import AsyncGenerator
+
 
 def test_asyncgen_basics() -> None:
     collected = []

trio/_core/_tests/test_guest_mode.py

@@ -29,7 +29,6 @@
 
 import trio
 import trio.testing
-from trio._channel import MemorySendChannel
 from trio.abc import Instrument
 
 from ..._util import signal_raise
@@ -38,6 +37,8 @@
 if TYPE_CHECKING:
     from typing_extensions import TypeAlias
 
+    from trio._channel import MemorySendChannel
+
 T = TypeVar("T")
 InHost: TypeAlias = Callable[[object], None]
 

trio/_core/_tests/test_instrumentation.py

@@ -1,14 +1,16 @@
 from __future__ import annotations
 
-from typing import Container, Iterable, NoReturn
+from typing import TYPE_CHECKING, Container, Iterable, NoReturn
 
 import attr
 import pytest
 
 from ... import _abc, _core
-from ...lowlevel import Task
 from .tutil import check_sequence_matches
 
+if TYPE_CHECKING:
+    from ...lowlevel import Task
+
 
 @attr.s(eq=False, hash=False)
 class TaskRecorder(_abc.Instrument):

trio/_core/_tests/test_io.py

@@ -2,7 +2,6 @@
 
 import random
 import socket as stdlib_socket
-from collections.abc import Generator
 from contextlib import suppress
 from typing import TYPE_CHECKING, Awaitable, Callable, Tuple, TypeVar
 
@@ -16,6 +15,8 @@
 # Cross-platform tests for IO handling
 
 if TYPE_CHECKING:
+    from collections.abc import Generator
+
     from typing_extensions import ParamSpec
 
     ArgsT = ParamSpec("ArgsT")

trio/_core/_tests/test_multierror.py

@@ -9,8 +9,7 @@
 import warnings
 from pathlib import Path
 from traceback import extract_tb, print_exception
-from types import TracebackType
-from typing import Callable, NoReturn
+from typing import TYPE_CHECKING, Callable, NoReturn
 
 import pytest
 
@@ -19,6 +18,9 @@
 from .._multierror import MultiError, NonBaseMultiError, concat_tb
 from .tutil import slow
 
+if TYPE_CHECKING:
+    from types import TracebackType
+
 if sys.version_info < (3, 11):
     from exceptiongroup import ExceptionGroup
 

trio/_core/_tests/test_run.py

@@ -8,16 +8,9 @@
 import time
 import types
 import weakref
-from collections.abc import (
-    AsyncGenerator,
-    AsyncIterator,
-    Awaitable,
-    Callable,
-    Generator,
-)
 from contextlib import ExitStack, contextmanager, suppress
 from math import inf
-from typing import Any, NoReturn, TypeVar, cast
+from typing import TYPE_CHECKING, Any, NoReturn, TypeVar, cast
 
 import outcome
 import pytest
@@ -39,6 +32,15 @@
     slow,
 )
 
+if TYPE_CHECKING:
+    from collections.abc import (
+        AsyncGenerator,
+        AsyncIterator,
+        Awaitable,
+        Callable,
+        Generator,
+    )
+
 if sys.version_info < (3, 11):
     from exceptiongroup import BaseExceptionGroup, ExceptionGroup
 

trio/_core/_tests/test_thread_cache.py

@@ -4,16 +4,18 @@
 import time
 from contextlib import contextmanager
 from queue import Queue
-from typing import Iterator, NoReturn
+from typing import TYPE_CHECKING, Iterator, NoReturn
 
 import pytest
-from outcome import Outcome
 from pytest import MonkeyPatch
 
 from .. import _thread_cache
 from .._thread_cache import ThreadCache, start_thread_soon
 from .tutil import gc_collect_harder, slow
 
+if TYPE_CHECKING:
+    from outcome import Outcome
+
 
 def test_thread_cache_basics() -> None:
     q: Queue[Outcome[object]] = Queue()