compat.py

"""Stuff that differs in different Python versions and platform
distributions."""

import logging
import os
import sys

__all__ = ["get_path_uid", "stdlib_pkgs", "WINDOWS"]


logger = logging.getLogger(__name__)


def has_tls():
    # type: () -> bool
    try:
        import _ssl  # noqa: F401  # ignore unused

        return True
    except ImportError:
        pass

    from pip._vendor.urllib3.util import IS_PYOPENSSL

    return IS_PYOPENSSL


def get_path_uid(path):
    # type: (str) -> int
    """
    Return path's uid.

    Does not follow symlinks:
        https://github.com/pypa/pip/pull/935#discussion_r5307003

    Placed this function in compat due to differences on AIX and
    Jython, that should eventually go away.

    :raises OSError: When path is a symlink or can't be read.
    """
    if hasattr(os, "O_NOFOLLOW"):
        fd = os.open(path, os.O_RDONLY | os.O_NOFOLLOW)
        file_uid = os.fstat(fd).st_uid
        os.close(fd)
    else:  # AIX and Jython
        # WARNING: time of check vulnerability, but best we can do w/o NOFOLLOW
        if not os.path.islink(path):
            # older versions of Jython don't have `os.fstat`
            file_uid = os.stat(path).st_uid
        else:
            # raise OSError for parity with os.O_NOFOLLOW above
            raise OSError(f"{path} is a symlink; Will not return uid for symlinks")
    return file_uid


# packages in the stdlib that may have installation metadata, but should not be
# considered 'installed'.  this theoretically could be determined based on
# dist.location (py27:`sysconfig.get_paths()['stdlib']`,
# py26:sysconfig.get_config_vars('LIBDEST')), but fear platform variation may
# make this ineffective, so hard-coding
stdlib_pkgs = {"python", "wsgiref", "argparse"}


# windows detection, covers cpython and ironpython
WINDOWS = sys.platform.startswith("win") or (sys.platform == "cli" and os.name == "nt")