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
--- a/mercurial/debugcommands.py Sat Jan 18 10:43:52 2020 -0800
+++ b/mercurial/debugcommands.py Sat Jan 18 10:37:14 2020 -0800
@@ -3218,16 +3218,19 @@
raise error.Abort(_(b'cannot use both --logiofd and --logiofile'))
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:
- logfh = os.fdopen(int(opts[b'logiofd']), 'ab', 1)
+ 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', 1)
+ logfh = os.fdopen(int(opts[b'logiofd']), 'wb', 0)
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.serve_forever()