[Python-Dev] About raising NotPortableWarning for CPython specific code

[Terry Reedy]

On 3/12/2011 3:04 PM, Thomas Wouters wrote:

> It should be fixed, yes, but breaking existing code is going to piss off
> a lot of people (like me) who already have enough worries when upgrading
> Python. It is apparent that there *is* code out there that relies on
> this behaviour, we shouldn't break it wlily-nilly. A warning when
> CPython encounters the case that will change behaviour in the next
> CPython release and in other implementations is almost as good as
> changing the behaviour.

Every bug fix breaks code that depends on the bug. That said, we do not 
backport every bug fix. I think in the long run it would be good to fix 
at least 2.7 and 3.2, but that could be debated.

Greg Price, who started the thread wanting PyPy to replicate the 
somewhat undefined and crazy behavior of CPython, admits
"I think a strict reading of the language reference would clearly 
identify this as wrong behavior by CPython."
http://codespeak.net/pipermail/pypy-dev/2011q1/006966.html
So he can hardly complain if we fix the 'wrong behavior'.

He is not a newbie: he is the one who diagnosed why CPython behaves as 
it does. He also knows how to fix their code: simply add to each 
appended class an __iter__ method just like I did, except yield the same 
thing as the __radd__ method appends rather than something different. 
With such a fix, his software would work with buggy and fixed CPython as 
well PyPy. He should just do that.

He apparently is not the original author. Too bad *that* programmer did 
not recognize and report that he had discovered a bug. I doubt that too 
many other people have encountered it because I expect someone would 
have posted something.

-- 
Terry Jan Reedy