[Distutils] A smaller step towards de-specializing setuptools/distutils

[Robert Collins]

On 30 October 2015 at 11:50, Robert Collins <robertc at robertcollins.net> wrote:
...
> However, the big step you're proposing that I think is fundamentally
> unsound is that of requiring a wheel be built before dependencies can
> be queried. Wheels are *expensive* to build in enough cases that I
> really believe we have a choice between being able to fix issue 988 or
> utilising wheels as the interface to get at install metadata. Remember
> too that the numpy ABI discussion is going to cause install
> dependencies to depend on the version of numpy present at build-time,
> so the resolver is going to have to re-evaluate the dependencies for
> those distributions when it selects a new numpy version: so its not
> even a one-time-per-package cost, its a
> one-time-per-arc-of-the-N!-graph-paths cost.

On further thought there is one mitigating factor here - we'd have to
be building numpy fully anyway for the cases where numpy is a
build-dependency for things further up the stack, so even in my most
paranoid world we will *anyway* have to pay that cost - but we can
avoid the cost of multiple full rebuilds of C extensions built on top
of numpy. I think avoiding that cost is still worth it, its just a
little more into the grey area rather than being absolutely obviously
worth it.

-Rob


-- 
Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud