Re: [PATCH] IPython: Use 'python2-variant'.

[Leo Famulari <leo@famulari.name>]

On Sun, Apr 17, 2016 at 10:54:03AM +1000, Ben Woodcroft wrote:
> Hi,
> 
> This hopefully should be a pretty straightforward patch, but I just wanted
> to check that I was doing the correct thing this first time. Seems to make
> the code much cleaner.
> 
> Does it make sense to go through all the python packages and convert them
> all to the python2-variant style? As I understand the idea is to do this one
> package per commit, which means traversing python dependency graph? Is
> anyone on this?

What do you mean by "all the python packages"? I think that if a plain
and unadorned package-with-python2 works for a package, then we should
not change the package to use the python2-variant system.

The python2-variant system is really for packages that require different
inputs or build arguments for the python-2 and python-3 versions. Some
of these packages were causing problems throughout the dependency graph
before introducing this system. For example, see how Ludo untangled some
knotty code beginning with 00f2bf34. And again in 519e2f4fd.

My plan was to switch remaining "difficult" packages to python2-variant
when they started causing problems, or when we were going to be changing
a package anyways.

But, if you want to make the changes and check that all the affected
packages still work, then I don't see a reason not to do it :)

By the way, here is the bug report on this topic:
http://bugs.gnu.org/22437

>  (define-public python2-ipython
> -  (let ((ipython (package-with-python2 python-ipython)))
> +  (let ((parent (package-with-python2
> +                 (strip-python2-variant python-ipython))))

I prefer to the upstream name (ipython) rather than "parent". Some
people use "base". I'd rather not introduce a 3rd option ;)

Otherwise it looks okay, assuming you've tested that the referring
packages still work as expected.