[New-bugs-announce] [issue26185] zipfile.ZipInfo slots can raise unexpected AttributeError

[Matthew Zipay]

New submission from Matthew Zipay:

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.

----------
components: Library (Lib)
files: zipfile.ZipInfo.patch
keywords: patch
messages: 258859
nosy: Matthew Zipay
priority: normal
severity: normal
status: open
title: zipfile.ZipInfo slots can raise unexpected AttributeError
type: behavior
versions: Python 3.5, Python 3.6
Added file: http://bugs.python.org/file41698/zipfile.ZipInfo.patch

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue26185>
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