[Python-Dev] Emit a BytesWarning on bytes filenames on Windows

[Victor Stinner]

Le 29/10/2011 07:47, Mark Hammond a écrit :
> When previously discussing this issue, I was under the impression that
> the problem was unencodable bytes passed from the Python code to Windows
> - but the reverse is true - only the data coming back from Windows isn't
> encodable.

The undecodable filenames issue occurs mostly on os.listdir(bytes) and 
os.getcwdb().

Unencodable filenames issue occurs on the rest of my function list.

> As the data came externally, the only solution the programmer
> has is to change to the unicode version of the api
> - so we recommend the bytes version not be used by anyone,
> anytime - which means it is conceptually deprecated already.

I proposed to raise a Unicode error on undecodable filenames, instead of 
returning invalid filenames (with question marks), to force the 
developer to move to the Unicode API. But as I explained in my previous 
message, you have to wait for an user having the problem to be noticied 
of the problem.

Terry J. Reedy is also concerned about backward compatibility (3.2 -> 
3.3). Emiting a warning, disabled by default, is a softer solution :-)

> Therefore, as you imply, I think the solution to this issue is to start
> the process of deprecating the bytes version of the api in py3k with a
> view to removing it completely - possibly with a less aggressive
> timeline than normal.

If there is a warning, I don't really care of removing the bytes API 
before Python 4.

PendingDeprecationgWarning can be used, or maybe a DeprecationWarning 
mentioning that the code will stay for long time.

> In Python 2.7, I think documenting the issue and a
> recommendation to always use unicode is sufficient (ie, we can't
> deprecate it and a new BytesWarning seems gratuitous.)

Sorry, I don't understand "gratuitous" here: do you mean that a new 
warning would annoying, and that it is cheap and useful to add it to 
Python 2.7.x?

Victor