[Python-Dev] os.path.commonprefix breakage

[Tim Peters]

I agree this is Bad Damage, and should be fixed before 2.0b1 goes out.  Can
you enter a bug report?

> -----Original Message-----
> From: python-dev-admin@python.org [mailto:python-dev-admin@python.org]On
> Behalf Of Mark Hammond
> Sent: Wednesday, August 16, 2000 11:32 PM
> To: python-dev@python.org
> Subject: [Python-Dev] os.path.commonprefix breakage
>
>
> Hi,
> 	I believe that Skip recently made a patch to
> os.path.commonprefix to only
> return the portion of the common prefix that corresponds to a directory.
>
> I have just dicovered some code breakage from this change.  On 1.5.2, the
> behaviour was:
>
> >>> os.path.commonprefix(["../foo/bar", "../foo/spam"])
> '../foo/'
>
> While since the change we have:
> '../foo'
>
> Note that the trailing slash has been dropped.
>
> The code this broke did similar to:
>
> prefix = os.path.commonprefix(files)
> for file in files:
>   tail_portion = file[len(prefix):]
>
> In 1.6, the "tail_portion" result looks like an absolute path "/bar" and
> "/spam", respectively.  The intent was obviously to get absolute
> path names
> back ("bar" and "spam")
>
> The code that broke is not mine, so you can safely be horrified at how
> broken it is :-)  The point, however, is that code like this does
> exist out
> there.
>
> I'm obviously going to change the code that broke, and don't have time to
> look into the posixpath.py code - but is this level of possible breakage
> acceptable?
>
> Thanks,
>
> Mark.