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Differential D4475

setup: don't support py 3.5.0, 3.5.1, 3.5.2 because of bug in codecs
ClosedPublic

Authored by pulkit on Sep 4 2018, 4:12 PM.

Details

Reviewers
indygreg
Group Reviewers
hg-reviewers
Commits
rHGb6b9488aae4c: setup: don't support py 3.5.0, 3.5.1, 3.5.2 because of bug in codecs
Summary

codecs.escape_encode() raises SystemError if an empty bytestring is passed. We
do that at some places in our code and because of this bug, things break.
Therefore we can't support the mentioned version. The bug was fixed in 3.5.3,
3.6.0 beta 2. We can't support 3.6.0 anyway because of bug in formatting
bytestrings.

Link to the python bug: https://bugs.python.org/issue25270

Diff Detail

Repository
rHG Mercurial
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Automatic diff as part of commit; lint not applicable.
Unit
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

pulkit created this revision.Sep 4 2018, 4:12 PM
indygreg accepted this revision.Sep 4 2018, 5:11 PM
indygreg added a subscriber: indygreg.

I'm a bit wary of version sniffing for the same reason that User-Agent sniffing is bad in web design: it assumes that version number strings map to behavior. The best way to test for compatibility is to actually test for the feature/behavior and then act appropriately. For example, setup.py would try running codecs.escape_encode(b'') and then bail if the buggy behavior is encountered.

I'm not 100% sure it applies in this case, but it is common for distros to backport Python fixes from future versions. For example, RHEL/CentOS 7 have a Python 2.7.5 with the modern ssl module (which was introduced in 2.7.9). And I know the Debian Python packages also commonly backport fixes.

That being said, we don't yet support Python 3 and we may not even support Python 3.5 by the time we do officially support Python 3. So I'm OK with this patch as a stop-gap. We can always improve detection later if version sniffing is problematic in the wild.

This revision is now accepted and ready to land.Sep 4 2018, 5:11 PM
durin42 added a comment.Sep 12 2018, 10:52 AM
In D4475#68453, @indygreg wrote:

I'm a bit wary of version sniffing for the same reason that User-Agent sniffing is bad in web design: it assumes that version number strings map to behavior. The best way to test for compatibility is to actually test for the feature/behavior and then act appropriately. For example, setup.py would try running codecs.escape_encode(b'') and then bail if the buggy behavior is encountered.

The version-sniffing here is actually done by pip when considering what wheels etc to download, so it will actually help the user out considerably as I understand it.

Closed by commit rHGb6b9488aae4c: setup: don't support py 3.5.0, 3.5.1, 3.5.2 because of bug in codecs (authored by pulkit). · Explain WhySep 12 2018, 10:54 AM
This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

PathPackages
Msetup.py (6 lines)

Diff 10946

setup.py

# #
# This is the mercurial setup script. # This is the mercurial setup script.
# #
# 'python setup.py install', or # 'python setup.py install', or
# 'python setup.py --help' for more options # 'python setup.py --help' for more options
import os import os
supportedpy = '~= 2.7' supportedpy = '~= 2.7'
if os.environ.get('HGALLOWPYTHON3', ''): if os.environ.get('HGALLOWPYTHON3', ''):
# Mercurial will never work on Python 3 before 3.5 due to a lack # Mercurial will never work on Python 3 before 3.5 due to a lack
# of % formatting on bytestrings, and can't work on 3.6.0 or 3.6.1 # of % formatting on bytestrings, and can't work on 3.6.0 or 3.6.1
# due to a bug in % formatting in bytestrings. # due to a bug in % formatting in bytestrings.
# We cannot support Python 3.5.0, 3.5.1, 3.5.2 because of bug in
# codecs.escape_encode() where it raises SystemError on empty bytestring
# bug link: https://bugs.python.org/issue25270
# #
# TODO: when we actually work on Python 3, use this string as the # TODO: when we actually work on Python 3, use this string as the
# actual supportedpy string. # actual supportedpy string.
supportedpy = ','.join([ supportedpy = ','.join([
'>=2.7', '>=2.7',
'!=3.0.*', '!=3.0.*',
'!=3.1.*', '!=3.1.*',
'!=3.2.*', '!=3.2.*',
'!=3.3.*', '!=3.3.*',
'!=3.4.*', '!=3.4.*',
'!=3.5.0',
'!=3.5.1',
'!=3.5.2',
'!=3.6.0', '!=3.6.0',
'!=3.6.1', '!=3.6.1',
]) ])
import sys, platform import sys, platform
if sys.version_info[0] >= 3: if sys.version_info[0] >= 3:
printf = eval('print') printf = eval('print')
libdir_escape = 'unicode_escape' libdir_escape = 'unicode_escape'