[gentoo-python] distutils-r1 -- support for out-of-source builds?

[Michał Górny]

Hello,

The original distutils.eclass uses out-of-source builds by default.
distutils-r1 (following the scheme of p-d-ng) just copies the sources
and does in-source builds unconditionally. I'm wondering about changing
that.

The change would mean that:

1) out-of-source (build-dir) builds are used by default,

2) in-source builds (and copying sources) is enabled through setting
DISTUTILS_IN_SOURCE_BUILD *or* whenever python_prepare() is declared
(since that function supposedly is used to modify sources),

3) a wrapper function for setup.py is introduced (esetuppy? edistsetup?)
which calls setup.py with correct build-dir,

4) ebuilds defining python_test() (and no python_prepare()) would need
to be updated to use the above-mentioned wrapper.

I'm wondering whether it's a good idea to change that. The main benefit
is that:

a) we avoid unnecessary copy in most cases,

b) we increase compatibility with distutils.eclass; e.g. the following
would start working:

  src_prepare() {
    distutils-r1_src_prepare
    sed ...
  }

which currently fails silently since sed is performed after copying
sources.

On the other hand, we would introduce a tiny bit of additional code.

-- 
Best regards,
Michał Górny