On Wed, 03 Jun 2020 05:46:05 +0200, Manuel Jacob wrote:
> On 2020-06-03 00:04, Augie Fackler wrote:
> >> On Jun 2, 2020, at 14:07, Manuel Jacob <m...@manueljacob.de> wrote:
> >>
> >> # HG changeset patch
> >> # User Manuel Jacob <m...@manueljacob.de>
> >> # Date 1591120869 -7200
> >> # Tue Jun 02 20:01:09 2020 +0200
> >> # Branch stable
> >> # Node ID ebbc45544673c33ea3beb887ed4d5230b015102a
> >> # Parent 91e509a12dbc4cd6cf2dcb9dae3ed383932132ac
> >> py3: always flush ui streams on Python 3
> >>
> >> On Python 2, we rely on that stdout and stderr are line buffered.
> >> Python 3’s
> >> io module doesn’t offer line buffered binary streams.
> >
> > We use the underlying non-buffer thing though for std{err, out}
> > though, or so I thought. Are you observing behavior that this
> > corrects?
>
> pycompat says:
>
> stdout = sys.stdout.buffer
> stderr = sys.stderr.buffer
>
> They are <_io.BufferedWriter name='<stdout>'> and <_io.BufferedWriter
> name='<stderr>'>, respectively.
>
> I observed the error in TortoiseHg, which is a long-running process.
>
> To trigger the problem with the hg command, you would need to do
> something slow that prints on `self._fout`, e.g. `hg pull
> https://www.mercurial-scm.org/repo/hg --debug`.
Denis, do you have any idea? My assumption was sys.stdout.buffer was magically
line-buffered, but it appears not at least with Python 3.8.3 on Linux.
https://www.mercurial-scm.org/repo/hg/rev/227ba1afcb65
> >> --- a/mercurial/ui.py
> >> +++ b/mercurial/ui.py
> >> @@ -1198,9 +1198,14 @@ class ui(object):
> >> label = opts.get('label', b'')
> >> msg = self.label(msg, label)
> >> dest.write(msg)
> >> + # On Python 2, stdout and stderr are usually line
> >> buffered, but
> >> # stderr may be buffered under win32 when redirected to
> >> files,
> >> # including stdout.
> >> - if dest is self._ferr and not getattr(self._ferr,
> >> 'closed', False):
> >> + # On Python 3, we use the underlying binary buffer, which
> >> does not
> >> + # support line buffering.
> >> + if (pycompat.ispy3 or dest is self._ferr) and not
> >> getattr(
> >> + self._ferr, 'closed', False
> >> + ):
> >> dest.flush()
Flushing stdout per write() sounds bad. If that's the only way to work
around Py3 io module, we'll probably need to check if the stdout is
a tty or not.
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