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sys.exitfunc should raise a Py3K warning when set/used.

A fixer to use the atexit module is needed.

Actually, a fixer probably won't work since that would require the
atexit module to be imported.

This is going to be very hard to implement without module descriptors.
It might be better to make a 2to3 fixer which inserts an import too.

On Thu, Aug 21, 2008 at 6:43 AM, Benjamin Peterson
<report@bugs.python.org> wrote:
>
> Benjamin Peterson <musiccomposition@gmail.com> added the comment:
>
> This is going to be very hard to implement without module descriptors.
> It might be better to make a 2to3 fixer which inserts an import too.
>
So for every sys import you are going to add an "import atexit"? That
doesn't seem reasonable. And if the call is in an expression context
you definitely cannot add the import.

On Thu, Aug 21, 2008 at 1:21 PM, Brett Cannon <report@bugs.python.org> wrote:
>
> So for every sys import you are going to add an "import atexit"? That
> doesn't seem reasonable. And if the call is in an expression context
> you definitely cannot add the import.
You're right; it's not going to be perfect, but 2to3 could warn when
it couldn't insert the import statement.
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue2356>
> _______________________________________
>

On Thu, Aug 21, 2008 at 11:45 AM, Benjamin Peterson
<report@bugs.python.org> wrote:
>
> Benjamin Peterson <musiccomposition@gmail.com> added the comment:
>
> On Thu, Aug 21, 2008 at 1:21 PM, Brett Cannon <report@bugs.python.org> wrote:
>>
>> So for every sys import you are going to add an "import atexit"? That
>> doesn't seem reasonable. And if the call is in an expression context
>> you definitely cannot add the import.
>
> You're right; it's not going to be perfect, but 2to3 could warn when
> it couldn't insert the import statement.
>>
OK, I can live with that.

Here's my 2to3 fixer for the cause. It always changes assignment to
sys.exitfunc to atexit.register. It then inserts a "import atexit" after
the module's sys import. If it can't find a sys import (that should be
rare obviously :) ), it emits a warning.

Since yesterday there is a handy little helper that adds imports to
files which is already used for the reduce() / intern() fixers. This
makes this fix a lot easier.
I attached a version that does that.
However the import adder is not yet as sophisticated as the one in the
previous patch, but the utility method could be improved to better adapt
to existing styleguides.

Here is an attempt to add a Py3K warning when sys.exitfunc is modified.

I've posted to python-dev asking for a reviewer for this, the thread is at http://mail.python.org/pipermail/python-dev/2010-March/098597.html 

Sean, are you referring to the warning or the 2to3 fixer?

Committed the 2to3 fixer in r79137.