Re: [gentoo-catalyst] Python 3 support

[Matthew Ruffalo]

On 05/21/2013 10:33 AM, Brian Dolbec wrote:
> On Tue, 2013-05-21 at 12:33 +0200, Dmitry Selyutin wrote:
>> Hello everyone!
>>
>> Since I'm going to reimplement catalyst in GSoC, I'd like to tell my
>> opinion if it has some weight. :-)
>> Some years have passed since Python 3 was created, and nowadays I
>> think it is stable enough to select it. I'd rather thought about
>> Python 2 compatibility than Python 3, since it seems to become a
>> standart soon. To cut a long story short, I'd rather oriented to
>> Python 3 than Python 2, though I prefer to use Python 2 nowadays. Of
>> course compatibility will be one of main aims, but I see some benefit
>> if we will choose Python 3 rather than Python 2, though users may
>> successfully use catalyst with Python 2 in the future. It's just a
>> proposal, so I'd like to hear your opinions. If you don't agree, we
>> may rather think about Python 2.
> Dmitry, It's not that I don't want it to be python3 compatible as an
> afterthought.  For the same reason as i told you already.  Catalyst is a
> python2 application and is working code.  It is better to fix all the
> poor areas of the code first before migrating to python3.  Also, that
> will fix some of the compatibility issues on it's own.  That way the
> changes can be properly tested.  Changing the code to py3 will bring
> enough bugs into the system on it's own.  It is far better to fix the
> poor code first.
>
>> Even more, I'd like to avoid some generators and provide this support
>> manually: I've always hated generators, especially code generators
>> (and GUI ones).
>>
>> What do you think about it?
> Catalyst should not need to have 2to3 run on it's codebase in the ebuild
> to be py3 compatible.  python2.6 and up are mostly py3 compatible
> already.  Catalyst does not do anything wild that should need porting
> between versions.  There are also a few tricks that can be done to
> simplify compatibility without the need for conversion runs.
Thank you all for the advice and feedback. Things like "don't base any 
real work on the master branch at 
git://git.overlays.gentoo.org/proj/catalyst.git" are exactly what I was 
hoping to hear.

Some other thoughts:

I wouldn't call what I'm proposing to do "refactoring". I've _used_ 
catalyst for quite a while but only looked at its code a few days ago. 
The extent of my changes would be "make it run on Python 3 and update 
some parts of the code to use newer/cleaner Python idioms".

Almost all of the bugs introduced in 2to3 conversion will be bytes/str 
related, and it's easy enough to decode() text that is read from a 
subprocess. Everything should be valid UTF-8, so there won't be any 
unpleasant character encoding issues.

It's likely that I'm wrong about this, but I don't think that there is 
much (any?) benefit to supporting Python 2 and Python 3 with the same 
code base. I have added 2to3 conversion to a few setup.py files, but 
these were in Python packages that still had to support Python 2 on 
multiple distributions. Catalyst is fundamentally a Gentoo 
_application_, and the implementation details don't really matter as 
long as it runs on current Gentoo systems. From my own experience as a 
user, I run the catalyst executable and I don't particularly care 
whether it's implemented in C, Java, Haskell, Python, INTERCAL, etc. I 
only care that I can 'emerge catalyst', make some tweaks to its files in 
/etc, and run 'catalyst'.

Since Python 3.2+ is available on all current Gentoo systems and will be 
from now on, I don't think there's anything to lose by doing a one-shot 
conversion and changing relevant hashbang lines to "#!/usr/bin/env python3".

(Brian: you may want to change 
http://dev.gentoo.org/~dolsen/catalyst/HEAD to contain "ref: 
refs/heads/rewrite" :) )

Thanks,
MMR...