zipfile.ZipInfo slots can raise unexpected AttributeError

[MatthewZipay]

BPO	26185
Nosy	@Yhg1s, @ned-deily, @DinoV, @takluyver, @serhiy-storchaka, @BoboTiG
PRs	bpo-26185: Fix repr() on empty ZipInfo object #13441
Files	zipfile.ZipInfo.patch: patch of Lib/zipfile.py and Lib/test/test_zipfile.py

^{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 2020-08-02.21:21:02.062>
created_at = <Date 2016-01-23.10:41:53.478>
labels = ['type-bug', 'library', '3.9']
title = 'zipfile.ZipInfo slots can raise unexpected AttributeError'
updated_at = <Date 2020-08-02.21:21:02.057>
user = 'https://bugs.python.org/MatthewZipay'

bugs.python.org fields:

activity = <Date 2020-08-02.21:21:02.057>
actor = 'ned.deily'
assignee = 'none'
closed = True
closed_date = <Date 2020-08-02.21:21:02.062>
closer = 'ned.deily'
components = ['Library (Lib)']
creation = <Date 2016-01-23.10:41:53.478>
creator = 'Matthew Zipay'
dependencies = []
files = ['41698']
hgrepos = []
issue_num = 26185
keywords = ['patch']
message_count = 4.0
messages = ['258859', '351452', '374694', '374697']
nosy_count = 8.0
nosy_names = ['twouters', 'alanmcintyre', 'ned.deily', 'dino.viehland', 'takluyver', 'serhiy.storchaka', 'Matthew Zipay', 'Tiger-222']
pr_nums = ['13441']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue26185'
versions = ['Python 3.9']

[MatthewZipay]

The zipfile.ZipInfo.__init__ method permits several of ZipInfo's slot attributes to go uninitialized unless the object is obtained from ZipFile.getinfo() or ZipFile.infolist().

As a result, accessing those attributes (header_offset, CRC, compress_size, or file_size) or attempting to repr() a ZipInfo object can fail unexpectedly with AttributeError. (I say "unexpectedly" because ZipInfo.__init__ and its attributes are public/documented, so the attributes ought to be properly initialized regardless of how the object gets created.)

A simple test to illustrate:

>>> import zipfile
>>> zinfo = zipfile.ZipInfo()
>>> repr(zinfo)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "********/cpython/Lib/zipfile.py", line 376, in __repr__
    result.append(' file_size=%r' % self.file_size)
AttributeError: file_size

(If you assign zinfo.file_size = None, it next fails on compress_size.)

This problem has been noted before - see issues 3039 and 22217 - but has not been resolved.

Patch including tests is attached.

[DinoV]

New changeset 992347d by Dino Viehland (Mickaël Schoentgen) in branch 'master':
bpo-26185: Fix repr() on empty ZipInfo object (bpo-13441)
992347d

[BoboTiG]

The ticket could be closed, right? The fix was merged quite some time ago.

[ned-deily]

Fixed in 3.9.0