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Differential D7948

debugcommands: move away from line buffered output on binary stream
ClosedPublic

Authored by indygreg on Jan 18 2020, 4:18 PM.

Details

Reviewers
pulkit
Group Reviewers
hg-reviewers
Commits
rHG52f8b07ad2f9: debugcommands: move away from line buffered output on binary stream
rHG2ae43bc51483: debugcommands: move away from line buffered output on binary stream
Summary

Line buffering on binary file objects is apparently undefined behavior
in Python and emits a RuntimeWarning on Python 3.8. See
https://bugs.python.org/issue32236.

This commit changes the I/O logging file descriptor from line
buffered to unbuffered to work around this. I'm no fan of
unbuffered I/O for performance reasons. But I don't think it
is an issue here given the nature of the code.

With this change, test-ssh-proto.t now passes on Python 3.8.

Diff Detail

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

Revision Contents
Changeset List

PathPackages
Mmercurial/debugcommands.py (11 lines)

Diff 19471

mercurial/debugcommands.py

raise error.Abort(_(b'only --sshstdio is currently supported')) raise error.Abort(_(b'only --sshstdio is currently supported'))
logfh = None logfh = None
if opts[b'logiofd'] and opts[b'logiofile']: if opts[b'logiofd'] and opts[b'logiofile']:
raise error.Abort(_(b'cannot use both --logiofd and --logiofile')) raise error.Abort(_(b'cannot use both --logiofd and --logiofile'))
if opts[b'logiofd']: if opts[b'logiofd']:
# Line buffered because output is line based. # Ideally we would be line buffered. But line buffering in binary
# mode isn't supported and emits a warning in Python 3.8+. Disabling
# buffering could have performance impacts. But since this isn't
# performance critical code, it should be fine.
try: try:
logfh = os.fdopen(int(opts[b'logiofd']), 'ab', 1) logfh = os.fdopen(int(opts[b'logiofd']), 'ab', 0)
except OSError as e: except OSError as e:
if e.errno != errno.ESPIPE: if e.errno != errno.ESPIPE:
raise raise
# can't seek a pipe, so `ab` mode fails on py3 # can't seek a pipe, so `ab` mode fails on py3
logfh = os.fdopen(int(opts[b'logiofd']), 'wb', 1) logfh = os.fdopen(int(opts[b'logiofd']), 'wb', 0)
elif opts[b'logiofile']: elif opts[b'logiofile']:
logfh = open(opts[b'logiofile'], b'ab', 1) logfh = open(opts[b'logiofile'], b'ab', 0)
s = wireprotoserver.sshserver(ui, repo, logfh=logfh) s = wireprotoserver.sshserver(ui, repo, logfh=logfh)
s.serve_forever() s.serve_forever()
@command(b'debugsetparents', [], _(b'REV1 [REV2]')) @command(b'debugsetparents', [], _(b'REV1 [REV2]'))
def debugsetparents(ui, repo, rev1, rev2=None): def debugsetparents(ui, repo, rev1, rev2=None):
"""manually set the parents of the current working directory """manually set the parents of the current working directory