[Python-Dev] Emit SyntaxWarning on unrecognized backslash escapes?

[Nick Coghlan]

On 24 February 2015 at 08:40, Nick Coghlan <ncoghlan at gmail.com> wrote:
> On 24 February 2015 at 07:39, Mark Lawrence <breamoreboy at yahoo.co.uk> wrote:
>> On 23/02/2015 21:27, Serhiy Storchaka wrote:
>>>
>>> On 23.02.15 21:58, Joao S. O. Bueno wrote:
>>>>
>>>> That happens all the time, and is this use case that should possibly
>>>> be addressed here - maybe
>>>> something as simple as adding a couple of paragraphs to different places
>>>> in the documentation could mitigate the issue. (in contrast to make a
>>>> tons of otherwise valid code
>>>> to become deprecated in a couple releases).
>>>
>>>
>>> The problem is that the user don't know that he should read the
>>> documentation. It just find that his script works with "C:\sample.txt",
>>> but doesn't work with "D:\test.txt". He has no ideas what happen.
>>
>> Isn't this why users have help desks?
>
> Most don't, and cases like "\n" or "\t" in a Windows path name being
> converted to whitespace are utterly impossible to look up in an
> internet search when they fail, so a user learning on their own gets
> left with a broken program and no particularly effective ways to ask
> for help figuring it out.
>
> Like Unicode encoding errors they may appear a long way from the
> source of the offending data value (in this case, likely to be a file
> name copy and pasted from elsewhere on their system), and they don't
> give a particularly helpful error message (especially when the escape
> sequences are for whitespace).
>
> While I originally disliked the idea, I think this is a genuine
> usability issue on Windows that would be worth addressing. However,
> it's a significant enough change that I believe it needs a PEP and a
> reasonably long transition period before anything actually breaks. For
> example:
>
> - pep8 and pylint warnings as soon as a patch can be accepted
> - Py3kWarning in Python 2.7.x
> - DeprecationWarning in Python 3.5
> - SyntaxWarning in Python 3.6
> - SyntaxError in Python 3.7

Another suggestion: we may want to turn this particular deprecation
warning on by default in the interactive interpreter, and recommend
that other interactive interpreter developers (such as the IPython
folks) consider doing the same.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia