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[Python-ideas] os.path.cansymlink(path)

Oleg Broytman phd at phdru.name
Fri Jul 25 12:23:40 CEST 2014 
Hi!

On Thu, Jul 24, 2014 at 07:51:08PM +0300, anatoly techtonik <techtonik at gmail.com> wrote:
> This is a live code from current virtualenv.py:
> 
>     if hasattr(os, 'symlink'):
>         logger.info('Symlinking Python bootstrap modules')
> 
> This code is wrong, because OS support for
> symlinks doesn't guarantee that mounted filesystem
> can do this, resulting in OSError at runtime. So, the
> proper check would be to check if specific path
> supports symlinking.
> 
> The idea is:
> 
>     os.path.cansymlink(path)  - Return True if filesystem
>         of specified path can be symlinked.
> 
> Yes/No/Opinions?

   Such function (if it would be a function) should return one of three
answer, not two. Something like:

None - I don't know if the OS/fs support symlinks because another
       OSError occurred during test (perhaps not enough rights to write
       to the path);
False- the path clearly doesn't support symlinks;
True - the path positively supports symlinks.

   Implement the function in a module and publish the module at PyPI.
Warn users (in accompanying docs) that even if a path supports (or
doesn't support) symlinks this says nothing about any subpath of the
path because a subpath can be a mount of a different fs.

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            phd at phdru.name
           Programmers don't die, they just GOSUB without RETURN.
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