[Distutils] RFC PEP 386 : Version comparisons

[Tarek Ziadé]

On Sun, Jul 5, 2009 at 6:26 PM, Tres Seaver<tseaver at palladion.com> wrote:
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> Tarek Ziadé wrote:
>> On Sat, Jul 4, 2009 at 8:12 PM, Tres Seaver<tseaver at palladion.com> wrote:
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>>> Tarek Ziadé wrote:
>>>
>>>> back to that discussion, after re-reading all the threads I have a proposal :
>>>>
>>>> 1- let's add as we said "install_requires" in PEP 345 and describe in
>>>> it that people can define requirements,
>>>>   but without giving them rules for the version schemes.
>>>>
>>>>   We will just write in that PEP that it's up to the *dependency
>>>> manager* (pip, setuptools, zc.buildout, etc)
>>>>   to provide a cmp() for the version.
>>>>
>>>>   The only rule will be that each dependency is described like this :
>>>>
>>>>      dist_name [<|>|==|!=|>=|<=] version
>>>>
>>>>   where version is free and dist_name in [a-zA-Z0-9]
>>>>
>>>> 2- let's drop PEP 386 completely
>>> - -1.  I would rather exclude some use cases (post releases), than drop
>>> standardization altogether.
>>
>> Would you be OK to say in PEP 345 that a suggested tool to compare
>> versions could be
>> verlib (released as a third-party software), but that any system could
>> also be used to compare versions ?
>
> The purpose of defining the 'Requires-Dist' field in PEP 345 is to allow
> for a standardized way of spelling dependences.  If we don't standardize
> on the versioning, then we won't have gained any ground:  we might as
> well punt and keep using setuptools, and *forbid* putting versions into
> 'Requires-Dist' at all.

The purpose of 'Requires-Dist' is to allow spelling dependencies so that
a package manager can use these declaration to work. Distutils is not
that package
manager. I don't see what is wrong in not forcing a version comparison
function, but just specifying the "dist_name [<|>|==|!=|>=|<=] version" field
where the "version" part sorting order is decided by a package manager.

>
>> So we can move on and propose the PEP 345 change unindependantly from
>> a version comparison tool.
>
> I don't understand why we can't just settle on the reduced set:  the
> exotic cases aren't supported today (in distutils), and are mappable
> onto the verlib case with some effort.
>

To allow a developer that has created his own package manager on the
top of Distutils, to work with
his own way with versions numbers, without being forced by Distutils
to follow any particular
version scheme if he wants to use 'Requires-Dist'.

If we force the rule at distutils level, that means we are are saying
that distutils *is* a package manager .