pre-commit/pre_commit/xargs.py at map-manifest · pre-commit/pre-commit · GitHub

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from __future__ import annotations

import concurrent.futures

import contextlib

import math

import multiprocessing

import os

import subprocess

import sys

from collections.abc import Callable

from collections.abc import Generator

from collections.abc import Iterable

from collections.abc import MutableMapping

from collections.abc import Sequence

from typing import Any

from typing import TypeVar

from pre_commit import parse_shebang

from pre_commit.util import cmd_output_b

from pre_commit.util import cmd_output_p

TArg = TypeVar('TArg')

TRet = TypeVar('TRet')

def cpu_count() -> int:

try:

# On systems that support it, this will return a more accurate count of

# usable CPUs for the current process, which will take into account

# cgroup limits

return len(os.sched_getaffinity(0))

except AttributeError:

pass

try:

return multiprocessing.cpu_count()

except NotImplementedError:

return 1

def _environ_size(_env: MutableMapping[str, str] | None = None) -> int:

environ = _env if _env is not None else getattr(os, 'environb', os.environ)

size = 8 * len(environ) # number of pointers in `envp`

for k, v in environ.items():

size += len(k) + len(v) + 2 # c strings in `envp`

return size

def _get_platform_max_length() -> int: # pragma: no cover (platform specific)

if os.name == 'posix':

maximum = os.sysconf('SC_ARG_MAX') - 2048 - _environ_size()

maximum = max(min(maximum, 2 ** 17), 2 ** 12)

return maximum

elif os.name == 'nt':

return 2 ** 15 - 2048 # UNICODE_STRING max - headroom

else:

# posix minimum

return 2 ** 12

def _command_length(*cmd: str) -> int:

full_cmd = ' '.join(cmd)

# win32 uses the amount of characters, more details at:

# https://github.com/pre-commit/pre-commit/pull/839

if sys.platform == 'win32':

return len(full_cmd.encode('utf-16le')) // 2

else:

return len(full_cmd.encode(sys.getfilesystemencoding()))

class ArgumentTooLongError(RuntimeError):

pass

def partition(

cmd: Sequence[str],

varargs: Sequence[str],

target_concurrency: int,

_max_length: int | None = None,

) -> tuple[tuple[str, ...], ...]:

_max_length = _max_length or _get_platform_max_length()

# Generally, we try to partition evenly into at least `target_concurrency`

# partitions, but we don't want a bunch of tiny partitions.

max_args = max(4, math.ceil(len(varargs) / target_concurrency))

cmd = tuple(cmd)

ret = []

ret_cmd: list[str] = []

# Reversed so arguments are in order

varargs = list(reversed(varargs))

total_length = _command_length(*cmd) + 1

while varargs:

arg = varargs.pop()

arg_length = _command_length(arg) + 1

if (

total_length + arg_length <= _max_length and

len(ret_cmd) < max_args

ret_cmd.append(arg)

total_length += arg_length

elif not ret_cmd:

raise ArgumentTooLongError(arg)

else:

# We've exceeded the length, yield a command

ret.append(cmd + tuple(ret_cmd))

ret_cmd = []

total_length = _command_length(*cmd) + 1

varargs.append(arg)

ret.append(cmd + tuple(ret_cmd))

return tuple(ret)

@contextlib.contextmanager

def _thread_mapper(maxsize: int) -> Generator[

Callable[[Callable[[TArg], TRet], Iterable[TArg]], Iterable[TRet]],

if maxsize == 1:

yield map

else:

with concurrent.futures.ThreadPoolExecutor(maxsize) as ex:

yield ex.map

def xargs(

cmd: tuple[str, ...],

varargs: Sequence[str],

color: bool = False,

target_concurrency: int = 1,

_max_length: int = _get_platform_max_length(),

**kwargs: Any,

) -> tuple[int, bytes]:

"""A simplified implementation of xargs.

color: Make a pty if on a platform that supports it

target_concurrency: Target number of partitions to run concurrently

"""

cmd_fn = cmd_output_p if color else cmd_output_b

retcode = 0

stdout = b''

try:

cmd = parse_shebang.normalize_cmd(cmd)

except parse_shebang.ExecutableNotFoundError as e:

return e.to_output()[:2]

# on windows, batch files have a separate length limit than windows itself

if (

sys.platform == 'win32' and

cmd[0].lower().endswith(('.bat', '.cmd'))

): # pragma: win32 cover

# this is implementation details but the command gets translated into

# full/path/to/cmd.exe /c *cmd

cmd_exe = parse_shebang.find_executable('cmd.exe')

# 1024 is additionally subtracted to give headroom for further

# expansion inside the batch file

_max_length = 8192 - len(cmd_exe) - len(' /c ') - 1024

partitions = partition(cmd, varargs, target_concurrency, _max_length)

def run_cmd_partition(

run_cmd: tuple[str, ...],

) -> tuple[int, bytes, bytes | None]:

return cmd_fn(

*run_cmd, check=False, stderr=subprocess.STDOUT, **kwargs,

)

threads = min(len(partitions), target_concurrency)

with _thread_mapper(threads) as thread_map:

results = thread_map(run_cmd_partition, partitions)

for proc_retcode, proc_out, _ in results:

if abs(proc_retcode) > abs(retcode):

retcode = proc_retcode

stdout += proc_out

return retcode, stdout

pre-commit/pre_commit/xargs.py at map-manifest · pre-commit/pre-commit · GitHub

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