[Python-Dev] Proposing PEP 345 : Metadata for Python Software Packages 1.2

["Martin v. Löwis"]

> So that will happen in the code of course, but we need the PEP to state clearly
> wether metadata 1.0 and 1.1 should be dropped by implementations or not.

Ok. We should recommend that implementations support these versions
indefinitely. I see no point in dropping them.

But then, this is really up to the implementations.

>>> PEP 314 (PEP 345 predecessor) was implemented in a very particular manner:
>> PEP 314 was implemented multiple times - not only in distutils, but also
>> in PyPI (for example).
> 
> PyPI doesn't produce PKG-INFO files AFAIK, it just consumes them, no ?

Correct - but that's also an implementation of the PEP.

> I am referring to the implementation in Distutils that produces 1.0
> *or* 1.1 PKG-INFO files.

But it works both ways. Applications that consume then need to decide
what versions they want to consume.

>> Please do keep distutils out of PEP 345. The remaining occurrences
>> (such as what the "interpret_marker" function does) should be removed.
> 
> That's the reference implementation of a PEP 345 reader/writer that
> happens to be in the stdlin. For what reason should we remove it from
> the PEP ?

Because there shouldn't be a reference implementation. If we have
both a spec and an a reference implementation, then we need to define
what happens in case they conflict. If the reference implementation
is right, implementers of the PEP would *also* need to study the
reference implementation to find out what conforming behaviour is.

This is bad; the PEP should be the only definition of the metadata
format.

>>> This will be clearer I think.
>> It would be also incompatible with existing consumers that expect
>> a Python package to have an earlier version of the metadata.
>> Dropping 1.0 may be fine though - but again, this is out of scope
>> here.
> 
> I don't understand why you are saying this is out of scope. Shouldn't we
> state clearly in the PEP that 1.0 and 1.1 should not be used in the future ?

In terms of conformance, what would that mean? If I implement 1.0 (in
addition to also implementing 1.2), would I then be non-conforming
(because the PEP says I should not support 1.0)? For PyPI, that would
be fairly bad, as it will need to support earlier versions for many
years to come (at a minimum, 10 years).

Regards,
Martin