[Distutils] Updated drafts of metadata 2.0 (PEP 426 and PEP 440)

[Nick Coghlan]

On 23 Jun 2013 21:09, "Paul Moore" <p.f.moore at gmail.com> wrote:
>
> On 23 June 2013 08:05, Nick Coghlan <ncoghlan at gmail.com> wrote:
>>
>> PEP 426 has now been updated based on the feedback on this thread (and
>> to handle some "todo" items that were pending anyway):
>> http://hg.python.org/peps/rev/3f733fe7c06c
>
>
> Sorry I didn't think of this sooner, but I don't see in the PEP a brief
summary of precisely what metadata is required. From the "Core Metadata"
section I infer that a project with *only* Name and Version (and
Metadata-Version, which will be supplied by the build tool) is valid.
That's fine, but notably more permissive than earlier versions of the spec.

That's deliberate - the mandatory fields are just those where dependency
analysis can't work if they're missing.

> One thing I see is "Index servers MAY require that this field be
provided" for some metadata (e.g., Summary") which is fine, I guess, but
implies that somewhere, the rules for PyPI should be documented.

I think I'll just move the summary back up into the core metadata. You
can't make a sane index server without it, and it used to be mandatory, so
"maybe mandatory, maybe not" just makes things more complicated than they
need to be rather than simplifying anything.

> Also, is it true that build tools MAY require certain fields to be
provided? I'm pretty sure setup.py sdist does at present.
>
> My logic here is that previously I would go to the metadata PEP to check
precisely what fields I need when building my project. Now, I'm not sure
where I'd go. (Note that most of my projects are internal only, so it's
actually the extra distutils/setuptools requirements that interest me more
than those of PyPI...) I can imagine the answer would be "the documentation
of the individual tool" - but in reality said documentation often isn't
present (possibly because earlier metadata PEPs documented this information
centrally)

I expect tools to come into line with PEP 426 on that front over time.
Those that still generate legacy metadata will likely follow the legacy
requirements, and for tools with stronger opinions about what should be
provided, it will be up to the authors to document that properly.

Contributions to the Python packaging user guide (a shared introduction to
setuptools and pip) are also more than welcome (see
http://python-packaging-user-guide.readthedocs.org). Marcus has made a good
start based on the distribute guide (with less opinionated hyperbole), and
I expect it to settle down to something quite usable once pip 1.4 is
released and it can simply direct people towards setuptools 0.7+ as the
default build tool (plus "wheel" for bdist_wheel support) and pip 1.4+ as
the default installer (including support for installation from wheels, and
automatic use of cached local builds for installation from source).

We really don't want end users needing to read PEPs just to get started.

Cheers,
Nick.

>
> Paul
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