comparison mercurial/debugcommands.py @ 44123:52f8b07ad2f9

debugcommands: move away from line buffered output on binary stream

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.

Differential Revision: https://phab.mercurial-scm.org/D7948

44122:bf5a73243cd5

    if opts[b'logiofd'] and opts[b'logiofile']:
        raise error.Abort(_(b'cannot use both --logiofd and --logiofile'))

    if opts[b'logiofd']:
        # Line buffered because output is line based.
        try:
            logfh = os.fdopen(int(opts[b'logiofd']), 'ab', 1)
        except OSError as e:
            if e.errno != errno.ESPIPE:
                raise
            # can't seek a pipe, so `ab` mode fails on py3
            logfh = os.fdopen(int(opts[b'logiofd']), 'wb', 1)
    elif opts[b'logiofile']:
        logfh = open(opts[b'logiofile'], b'ab', 1)

    s = wireprotoserver.sshserver(ui, repo, logfh=logfh)
    s.serve_forever()

44123:52f8b07ad2f9

    if opts[b'logiofd'] and opts[b'logiofile']:
        raise error.Abort(_(b'cannot use both --logiofd and --logiofile'))

    if opts[b'logiofd']:
        # 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:
            logfh = os.fdopen(int(opts[b'logiofd']), 'ab', 0)
        except OSError as e:
            if e.errno != errno.ESPIPE:
                raise
            # can't seek a pipe, so `ab` mode fails on py3
            logfh = os.fdopen(int(opts[b'logiofd']), 'wb', 0)
    elif opts[b'logiofile']:
        logfh = open(opts[b'logiofile'], b'ab', 0)

    s = wireprotoserver.sshserver(ui, repo, logfh=logfh)
    s.serve_forever()