[Distutils] A possible refactor/streamlining of PEP 517

[Paul Moore]

On 7 July 2017 at 11:30, Nathaniel Smith <njs at pobox.com> wrote:
> Is it absolutely necessary to get this into the first PEP?

As far as I'm concerned, it's no more than a restating (and
simplification?) of all the discussions around building out of tree
via creating an sdist and unpacking it, or having the various prepare
files hooks. It's always been there and always been a requirement.

> This proposal creates substantial complications for build systems that default to doing in-place builds

Well, we're focused on build systems that will get a PEP 517
interface, so far the only concrete examples we have are flit (which
has no problem with this), enscons (which has no problem with it) and
probably setuptools, in some form (which needs out-of-tree builds
based on our experience with it in pip, although I concede that you
would argue that point).

Also, out of tree builds are something that pip is planning on
implementing, and for us it's therefore necessary to have hooks that
let us do that. The current version of the PEP provides those hooks,
and we're planning on using them to do out of tree builds. This new
suggestion is basically backend authors saying "you don't need to do
the out of place builds, we're willing to take responsibility for
that". If you're saying that you're not happy with that, then all that
will end up happening is we revert to the previous approach, and pip
implements out of tree builds based on that (and I guess you have the
same argument all over again on the PR for the pip change...)

Paul