[alpine] shutil.copytree fail to copy a direcotry with broken symlinks

[fruch]

BPO	28627
Nosy	@vadmium, @sroracle
Superseder	bpo-31940: copystat on symlinks fails for alpine -- faulty lchmod implementation?
Files	musl-eopnotsupp.patch

^{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 = <Date 2019-02-11.01:53:13.584>
created_at = <Date 2016-11-06.22:34:31.619>
labels = ['type-bug', 'library']
title = '[alpine] shutil.copytree fail to copy a direcotry with broken symlinks'
updated_at = <Date 2019-02-11.01:53:13.580>
user = 'https://bugs.python.org/fruch'

bugs.python.org fields:

activity = <Date 2019-02-11.01:53:13.580>
actor = 'benjamin.peterson'
assignee = 'none'
closed = True
closed_date = <Date 2019-02-11.01:53:13.584>
closer = 'benjamin.peterson'
components = ['Library (Lib)']
creation = <Date 2016-11-06.22:34:31.619>
creator = 'fruch'
dependencies = []
files = ['47540']
hgrepos = []
issue_num = 28627
keywords = ['patch']
message_count = 4.0
messages = ['280178', '280179', '315472', '315540']
nosy_count = 3.0
nosy_names = ['martin.panter', 'fruch', 'sroracle']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '31940'
type = 'behavior'
url = 'https://bugs.python.org/issue28627'
versions = ['Python 3.5', 'Python 3.6']

[fruch]

this fails on python3.5-alpine and python3.6-alpine
(works as fine in python2.7-alpine)

cd /bug && ln -s /broken_path/to_nowhere broken
python -c "import shutil; shutil.copytree('/bug', '/temp', symlinks=True)"

Dockerfile example here:
docker-library/python#155

cpython/Lib/shutil.py

Line 198 in c30098c

except NotImplementedError:

seem like its suppressing NotImplementedError, and in our case OsError with ENOSUP was raised

[fruch]

the failure looks like that:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python3.5/shutil.py", line 359, in copytree
    raise Error(errors)
shutil.Error: [('/bug/broken', '/temp/broken', "[Errno 95] Not supported: '/temp/broken'")]

[sroracle]

Actually the symlinks don't need to be broken. It fails for any kind of symlink
on musl.

$ ls -l /tmp/symtest
lrwxrwxrwx 1 mcrees mcrees 10 Apr 18 21:16 empty -> /var/empty
-rw-r--r-- 1 mcrees mcrees  0 Apr 18 21:16 regular
lrwxrwxrwx 1 mcrees mcrees 16 Apr 18 21:16 resolv.conf -> /etc/resolv.conf

$ python3
>>> import shutil; shutil.copytree('/tmp/symtest', '/tmp/symtest2', symlinks=True)
shutil.Error: [('/tmp/symtest/resolv.conf', '/tmp/symtest2/resolv.conf', "[Errno
95] Not supported: '/tmp/symtest2/resolv.conf'"), ('/tmp/symtest/empty',
'/tmp/symtest2/empty', "[Errno 95] Not supported: '/tmp/symtest2/empty'")]

$ ls -l /tmp/symtest2
total 0
lrwxrwxrwx 1 mcrees mcrees 10 Apr 18 21:16 empty -> /var/empty
-rw-r--r-- 1 mcrees mcrees  0 Apr 18 21:16 regular
lrwxrwxrwx 1 mcrees mcrees 16 Apr 18 21:16 resolv.conf -> /etc/resolv.conf

The implication of these bugs mean that things like pip may fail if it calls
shutil.copytree(..., symlinks=True) on a directory that contains symlinks(!)

Attached is a patch that works around the issue but does not address why chmod
is returning OSError instead of NotImplementedError.

[vadmium]

This looks like it may be covered by bpo-31940, about the “shutil.copystat” API. See Anthony’s initial proposal at <https://bugs.python.org/issue31940#msg305528\>.

Max: I think you need the “else” branch to reraise the exception if “errno” doesn’t match. Perhaps a test case would have picked this up.