[AstroPy] External packages in astropy

[Olе Streicher]

Perry Greenfield <perry at stsci.edu> writes:
> Yes. But I'm not sure what your point is. There are many projects that  
> use SIP so doing without it isn't feasible. Yes, we could release  
> patched version under a different name, but we aren't in the business  
> of making a "better" version of wcslib available, nor do we want to  
> incur the possible political headaches of appearing to compete with  
> the original.

I don't just see the python world separately, and I want to provide the
optimal experience on Debian for everyone :-) 

To give a current example: I just finished the (re-)packaging of the DS9
program which was a real nightmare because it included dozens of
external packages, some of them more than once, sometimes patched and so
on. Files from wcstools occurred 2-3 times, in different versions, one
of them with bugfixes, the other left without -- just because it was
used as sub-package of another package. This is not what I would call
good software quality, this is a complete mess. DS9 was thrown out of
almost all Linux distributions because of that.

Astropy will have the potential to build applications with a similar
complexity and lifetime as DS9. From the development experience with
DS9, it would probably at some point start to include astropy, some
older packages that are based on pywcs, and some C code that uses wcslib
(and, to complete that, probably also some code from wcstools). This is,
ofcourse, just a view into my private crystal ball :-)

So, the final version would incorporate three versions of wcslib, with
differences due to "political reasons" -- this sounds like a horror
scenario to me. I think, we should not start with this, but instead try
hard to get an agreement on a common philosophy here. In the moment, we
have the realistic chance to establish wcslib as the standard library
for that purpose, we should avoid any defragmentation here. 

For Debian, I don't want to make a difference between the plain wcslib
and pywcs: either SIP should be included into wcslib and is then in
pywcs and astropy (in the moment, it is not), or it is dangerous, and
then I see no reason to keep it for pywcs/astropy users.

The other distributions have a quite similar problem -- the
"wcslib-unbundle" patch I use comes in fact from Fedora Linux.

Best regards

Ole