[Distutils] Provisionally accepting PEP 517's declarative build system interface

[Jeremy Stanley]

On 2017-06-02 15:12:19 +0100 (+0100), Paul Moore wrote:
[...]
> I'm struggling to understand why building a sdist in flit should need
> a VCS. It bothers me that I'm missing something important about how
> backends will work, that explains why (for example) you can't create a
> sdist from an export of a VCS branch (i.e., without the VCS metadata).
[...]

Unrelated to flit, but I have similar needs to be able to make sure
my sdist version has a 1:1 correspondence to the name of a release
tag in my VCS. Making a commit to embed a version number in a file
in the VCS and then tagging that commit with the same version number
is 1. racy and 2. duplication of information which can (and
frequently has) led to confusing mistakes. As a result, I either
need the VCS metadata present to be able to construct the version
number which will get included in PKG-INFO _or_ I need a complex
build wrapper which extracts the metadata prior to the filtered tree
copy happening and plumbs it through (with an envvar or maybe
spontaneously generating a file on disk) so that the sdist builder
will know what version to embed.

Present day, this works fine as a setuptools entrypoint which can
inspect the VCS metadata at sdist creation time. It would be
unfortunate to lose such flexibility in whatever hook implementation
we end up with.
-- 
Jeremy Stanley
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