src/python/grpcio/_spawn_patch.py

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"""Patches the spawn() command for windows compilers.

Windows has an 8191 character command line limit, but some compilers
support an @command_file directive where command_file is a file
containing the full command line.
"""

from distutils import ccompiler
import os
import os.path
import shutil
import sys
import tempfile

MAX_COMMAND_LENGTH = 8191

_classic_spawn = ccompiler.CCompiler.spawn


def _commandfile_spawn(self, command):
    command_length = sum([len(arg) for arg in command])
    if os.name == 'nt' and command_length > MAX_COMMAND_LENGTH:
        # Even if this command doesn't support the @command_file, it will
        # fail as is so we try blindly
        print('Command line length exceeded, using command file')
        print(' '.join(command))
        temporary_directory = tempfile.mkdtemp()
        command_filename = os.path.abspath(
            os.path.join(temporary_directory, 'command'))
        with open(command_filename, 'w') as command_file:
            escaped_args = [
                '"' + arg.replace('\\', '\\\\') + '"' for arg in command[1:]
            ]
            command_file.write(' '.join(escaped_args))
        modified_command = command[:1] + ['@{}'.format(command_filename)]
        try:
            _classic_spawn(self, modified_command)
        finally:
            shutil.rmtree(temporary_directory)
    else:
        _classic_spawn(self, command)


def monkeypatch_spawn():
    """Monkeypatching is dumb, but it's either that or we become maintainers of
     something much, much bigger."""
    ccompiler.CCompiler.spawn = _commandfile_spawn