[Python-Dev] Emit a BytesWarning on bytes filenames on Windows (original) (raw)

Mark Hammond skippy.hammond at gmail.com
Sat Oct 29 07:47:01 CEST 2011

On 29/10/2011 9:52 AM, Victor Stinner wrote:

Hi,

I am not more conviced that raising a UnicodeEncodeError on unencodable characters is the right fix for the issue #13247. The problem with this solution is that you have to wait until an user get a UnicodeEncodeError. I have yet another proposition: emit a warning when a bytes filename is used. So it doesn't affect the default behaviour, but you can use -Werror to test if your program is fully Unicode compliant on Windows (without having to test invalid filenames). I don't know if a BytesWarning or a DeprecationWarning is more apropriate. It depends if we plan to drop support of bytes filenames on Windows later (in Python 3.5 or later).

When previously discussing this issue, I was under the impression that the problem was unencodable bytes passed from the Python code to Windows

This changes my opinion significantly :) I don't think raising an error is the right choice - there are almost certainly use-cases where the current behaviour works OK and we would break them (eg, not all files in a directory are likely to be unencodable). 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.

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. 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.)

Cheers,

Mark

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