Re: [PATCH 4 of 5] py3: stop subscripting socket.error

Sat, 15 Dec 2018 21:02:57 -0800 

On Mon, 10 Dec 2018 07:12:41 -0500, Yuya Nishihara <y...@tcha.org> wrote:


On Sun, 09 Dec 2018 23:39:33 -0500, Matt Harbison wrote:

I ended up with similar stdio errors trying to track down the bad http
status failures:

Traceback (most recent call last):
   File "c:\Users\Matt\hg\mercurial\ui.py", line 1033, in _writenobuf
     dest.flush()
OSError: [WinError 1] Incorrect function

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "c:\Users\Matt\hg\mercurial\hgweb\server.py", line 192, in do_hgweb 
     for chunk in self.server.application(env, self._start_response):
   File "c:\Users\Matt\hg\mercurial\hgweb\hgweb_mod.py", line 310, in
run_wsgi
     for r in self._runwsgi(req, res, repo):
   File "c:\Users\Matt\hg\mercurial\hgweb\hgweb_mod.py", line 430, in
_runwsgi
     return getattr(webcommands, cmd)(rctx)
   File "c:\Users\Matt\hg\mercurial\hgweb\webcommands.py", line 861, in
comparison
     context = parsecontext(web.config('web', 'comparisoncontext', '5'))
File "c:\Users\Matt\hg\mercurial\hgweb\hgweb_mod.py", line 117, in config 
     untrusted=untrusted)
   File "c:\Users\Matt\hg\mercurial\ui.py", line 517, in config
     untrusted=untrusted)
   File "c:\Users\Matt\hg\mercurial\ui.py", line 536, in _config
     self.develwarn(msg, 2, 'warn-config-unknown')
   File "c:\Users\Matt\hg\mercurial\ui.py", line 1790, in develwarn
     % (msg, fname, lineno, fmsg))
   File "c:\Users\Matt\hg\mercurial\ui.py", line 996, in write_err
     self._write(self._ferr, *args, **opts)
   File "c:\Users\Matt\hg\mercurial\ui.py", line 1006, in _write
     self._writenobuf(dest, *args, **opts)
   File "c:\Users\Matt\hg\mercurial\ui.py", line 1039, in _writenobuf
     raise error.StdioError(err)
mercurial.error.StdioError: [Errno 22] Incorrect function

I see that there's a TODO for pycompat.{stdin,stdout,stderr} to use a
silly wrapper instead of .buffer. But this feeble attempt didn't seem to 
help:
That's unrelated issue. A pseudo file object might not have .buffer, but a 
real stdio object should have one.
Perhaps, the underlying file descriptor would be messed up in Windows way. If we can know that prior to calling write(), stdio fds can be reattached to 
NUL. But I don't know if that's possible.
I'm not sure what to do with this info yet, but I just noticed that pager is also messed up on py3- the debug message about spawning the pager prints, but no output for the diff. Use --pager=no, and it shows up. So maybe there's a general problem with stdio of spawned children.
I've been wondering why we aren't spawning the server child process with stdout and stderr handles set to NUL. I know on Unix, the child prints a bit of info before it starts listening. But that never worked on Windows, and we've been abusing the lock file to convey error messages back to the parent. 


Another Py3 issue is that sys.stdin/stdout/stderr is None on pythonw.exe.
IIRC, this can be worked around by attaching NUL to fd=0-2, and open them. 

  nullfd = os.open(os.devnull, O_RDWR | O_BINARY)
  os.dup2(nullfd, 0)
  os.dup2(nullfd, 1)
  os.dup2(nullfd, 2)
  os.close(nullfd)
  stdin = os.fdopen(0, 'rb')
  stdout = os.fdopen(1, 'wb')
  stderr = os.fdopen(2, 'wb')

But it might break ui.isatty() since NUL is reported as a tty on Windows.



About NUL being a tty, maybe this will help?

        https://stackoverflow.com/a/3660125
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