[Python-Dev] test_sys failures

[Guido van Rossum]

On Dec 21, 2007 12:05 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> Guido van Rossum wrote:
> > When I build from scratch and run most tests (regrtest.py -uall) I get
> > some strange failures with test_sys.py:
> >
> > test test_sys failed -- Traceback (most recent call last):
> >   File "/usr/local/google/home/guido/python/py3kd/Lib/test/test_sys.py",
> > line 302, in test_43581
> >     self.assertEqual(sys.__stdout__.encoding, sys.__stderr__.encoding)
> > AssertionError: 'ascii' != 'ISO-8859-1'
> >
> > The same test doesn't fail when run in isolation.
> >
> > Interestingly, I saw this with 2.5 as well as 3.0, but not with 2.6!
> >
> > Any ideas?
>
> It looks like the chunk of code in TextIOWrapper might be getting
> different answers when trying to work out the encoding for stdin and
> stderr (not that I can see how that would happen...). Or maybe there is
> some way that test_sys could be seeing the temporary '__stderr__' entry
> that is put in place until the io module is available?
>
> What do you get for stdin/stdout/stderr.encoding at the interactive
> prompt? On Ubuntu, I get UTF-8 for all of them in both 3.0a2 and 2.5.1,
> but I'm not seeing the problem, either.
>
> Other values of possible interest:
>    os.device_encoding(1)
>    os.device_encoding(2)
>    locale.getpreferredencoding()
>
> Another possibility would be to throw some debugging code into io.py to
> print out the encoding name to stderr when file is 1 or 2.

No answers yet, but a clue, and anyone on OSX should now be able to
reproduce this (with 2.5, 2.6 or 3.0) as follows:

  ./python ./Lib/test/test_sys.py | cat

That is, the problem happens when stdout is redirected to a pipe (or a file).

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)