shutil.copyfile does not raise SpecialFileError for socket files

[chrahunt]

BPO	37700
Nosy	@cjerdonek, @chrahunt, @potomak
PRs	gh-81881: Raise a shutil.SpecialFileError when copying a Unix socket #16575

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-07-29.04:22:16.840>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'shutil.copyfile does not raise SpecialFileError for socket files'
updated_at = <Date 2021-12-11.18:41:20.112>
user = 'https://github.com/chrahunt'

bugs.python.org fields:

activity = <Date 2021-12-11.18:41:20.112>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-07-29.04:22:16.840>
creator = 'chrahunt'
dependencies = []
files = []
hgrepos = []
issue_num = 37700
keywords = ['patch']
message_count = 3.0
messages = ['348595', '348596', '348602']
nosy_count = 3.0
nosy_names = ['chris.jerdonek', 'chrahunt', 'potomak']
pr_nums = ['16575']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37700'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Linked PRs

• GH-81881: Raise SpecialFileError for sockets and devices in shutil.copyfile #142693

[chrahunt]

Currently shutil.copyfile only raises SpecialFileError for named pipes. When trying to use the function to copy a socket file, the exception raised depends on the platform, for example:

macOS: "[Errno 102] Operation not supported on socket: '/Users/guido/src/mypy/dmypy.sock'"
HP-UX: "[Errno 223] Operation not supported: 'example/foo'"
Solaris: "[Errno 122] Operation not supported on transport endpoint: 'example/foo'"
AIX: "[Errno 64] Operation not supported on socket: '../../example/foo'"
Linux: "[Errno 6] No such device or address: 'example/foo'"

This can be reproduced like:

    import os
    import shutil
    import socket
    import tempfile

    d = tempfile.mkdtemp()
    src = os.path.join(d, "src")
    dest = os.path.join(d, "dest")
    sock = socket.socket(socket.AF_UNIX)
    sock.bind(src)

    shutil.copyfile(src, dest)

Making shutil.copyfile raise SpecialFileError for socket files would improve the interface of this function since the same class of error could be ignored. This is mostly useful with shutil.copytree, which defaults to copyfile for its copy function.

[chrahunt]

See also: the comment from

cpython/Lib/shutil.py

Line 245 in e1b9002

# XXX What about other special files? (sockets, devices...)

:

XXX What about other special files? (sockets, devices...)

[cjerdonek]

This issue is being filed after coming up in pip's tracker here (in a comment by Guido): pypa/pip#5306 (comment)