[Python-Dev] [Python-checkins] cpython (3.2): Issue #12400: runtest() truncates the StringIO stream before a new test

[Victor Stinner]

Le mercredi 29 juin 2011 à 13:05 -0400, Terry Reedy a écrit :
> On 6/29/2011 11:30 AM, victor.stinner wrote:
> 
> > summary:
> >    Issue #12400: runtest() truncates the StringIO stream before a new test
> >
> > files:
> >    Lib/test/regrtest.py |  1 +
> >    1 files changed, 1 insertions(+), 0 deletions(-)
> >
> >
> > diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
> > --- a/Lib/test/regrtest.py
> > +++ b/Lib/test/regrtest.py
> > @@ -793,6 +793,7 @@
> >               if runtest.stringio is None:
> >                   runtest.stringio = io.StringIO()
> >               stream = runtest.stringio
> > +            stream.truncate(0)
> 
> You *MUST* seek to 0 to reset the file position, which I presume is your 
> intention. 'Resize' does not mean what you probably think is does (and 
> what I thought once either ;-).
> 
> "truncate(size=None)
> Resize the stream to the given size in bytes (or the current position if 
> size is not specified). The current stream position isn’t changed."
> 
>  >>> s=io.StringIO()
>  >>> s.write('abc')
> 3
>  >>> s.truncate(0)
> 0
>  >>> s.tell()
> 3
>  >>> s.write('abc')
> 3
>  >>> s.getvalue()
> '\x00\x00\x00abc'

Oh crap. I read _pyio source code and .truncate(0) was looking for the
right method to "reset" a StringIO. I tried .truncate(0) in a terminal,
but the zeros ('\x00') are "hidden". sys.stdout.write("\0") doesn't
print anything in my Linux terminal.

Fixed by commit 450209efe272, thank you.

Victor