[Python-Dev] os.path.exists() / os.path.isdir() inconsistency when dealing with gvfs directories

[Giampaolo Rodolà]

2012/6/27 Cameron Simpson <cs at zip.com.au>:
> On 27Jun2012 01:49, Giampaolo Rodolà <g.rodola at gmail.com> wrote:
> | I've just noticed a strange behavior when dealing with gvfs filesystems:
> |
> | giampaolo at ubuntu:~$ python -c "import os;
> | print(os.path.exists('/home/giampaolo/.gvfs'))"
> | True
> | giampaolo at ubuntu:~$ sudo su
> | root at ubuntu:~# python -c "import os;
> | print(os.path.exists('/home/giampaolo/.gvfs'))"
> | False
> |
> | This is due to os.stat() which internally fails with PermissionError (EACCES).
> | The same problem exists with os.path.isdir() which will return True as
> | limited user and False as root.
> | I'm not sure what's best to do here nor I know if there are other
> | cases other than when dealing with gvfs which can produce similar
> | behaviors but here's an idea:
> |
> | - make os.path.exists() return True in case of PermissionError because
> | that's supposed to mean there's an existing path to deny access to
>
> Definitely not.
>
> Firstly, if I ask about "a/b/c" and am denied access to "a/b", then it
> would be a lie to say "c" exists - it may not.

Right, I wasn't taking that into account.

> So I'd be +0.5 for making the docs more clear that True is reliable and
> False may merely mean "could not access".

+1.
I was about to propose a 'strict' parameter which lets the exception
propagate in case of errno != EACCES/EPERM but a doc fix is probably
just fine.
I'll file a bug report later today.

Regards,

--- Giampaolo
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