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Clean up type hints for subprocess #3557

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Merged
A5rocks merged 2 commits into from
Oct 23, 2026
+25 −7
Merged

Clean up type hints for subprocess #3557

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22c8927
Clean up type hints for subprocess
A5rocks Oct 23, 2026
b851385
Fix pyright verify-types
A5rocks Oct 23, 2026
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14 changes: 7 additions & 7 deletions src/trio/_subprocess.py
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Original file line number Diff line number Diff line change
Expand Up @@ -50,8 +50,6 @@

def pidfd_open(fd: int, flags: int) -> int: ...

from ._subprocess_platform import ClosableReceiveStream, ClosableSendStream

else:
can_try_pidfd_open = True
try:
Expand Down Expand Up @@ -171,9 +169,9 @@ def __init__(
if self.stdin is not None and self.stdout is not None:
self.stdio = StapledStream(self.stdin, self.stdout)

self._wait_lock: Lock = Lock()
self._wait_lock = Lock()

self._pidfd: FileIO | None = None
self._pidfd = None
if can_try_pidfd_open:
try:
fd: int = pidfd_open(self._proc.pid, 0)
Expand All @@ -188,6 +186,8 @@ def __init__(
# make sure it'll get closed.
self._pidfd = FileIO(fd)

# TODO: remove the following two type hints, required only due to
# https://github.com/microsoft/pyright/issues/11917
self.args: StrOrBytesPath | Sequence[StrOrBytesPath] = self._proc.args
self.pid: int = self._proc.pid

Expand Down Expand Up @@ -381,9 +381,9 @@ async def _open_process(
"shell=True on UNIX systems",
)

trio_stdin: ClosableSendStream | None = None
trio_stdout: ClosableReceiveStream | None = None
trio_stderr: ClosableReceiveStream | None = None
trio_stdin = None

@CoolCat467 CoolCat467 Oct 23, 2026

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I am surprised mypy strict mode is alright with this (then again I don't think we have that turned on be default)

Seeing this here and knowing this is likely a mypy strict mode thing, I wouldn't be surprised if this is one of my contributions for a future where we do enable strict mode

@A5rocks A5rocks Oct 23, 2026 •
edited
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mypy has a ton of special behavior around None where it will look around at context to figure out the right type hint.

See https://mypy-play.net/?mypy=latest&python=3.12&flags=strict&gist=2c203611ecce92bee7a12ef01ab7d524 for an example. (Also at some point I might switch us to using allow-redefinition, mypy's done a new version of it since I last tried that and probably it's less buggy!)

@CoolCat467 CoolCat467 Oct 23, 2026

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Gotcha. Looks like things have changed from what I remember we had to do previously.

trio_stdout = None
trio_stderr = None
# Close the parent's handle for each child side of a pipe; we want the child to
# have the only copy, so that when it exits we can read EOF on our side. The
# trio ends of pipes will be transferred to the Process object, which will be
Expand Down
18 changes: 18 additions & 0 deletions src/trio/_tests/type_tests/subprocesses.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,12 @@
import os
import sys
from collections.abc import Sequence
from typing import TypeAlias

import trio
from typing_extensions import assert_type

StrOrBytesPath: TypeAlias = str | bytes | os.PathLike[str] | os.PathLike[bytes]


async def test() -> None:
Expand All @@ -21,3 +27,15 @@ async def test() -> None:
# 3.11+:
await trio.run_process("python", process_group=5) # type: ignore
await trio.lowlevel.open_process("python", process_group=5) # type: ignore


def check_processes(proc: trio.Process) -> None:
assert_type(proc.stdin, trio.abc.SendStream | None)
assert_type(proc.stdout, trio.abc.ReceiveStream | None)
assert_type(proc.stderr, trio.abc.ReceiveStream | None)
assert_type(
proc.stdio,
trio.StapledStream[trio.abc.SendStream, trio.abc.ReceiveStream] | None,
)
assert_type(proc.args, StrOrBytesPath | Sequence[StrOrBytesPath])
assert_type(proc.pid, int)
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