[Distutils] Pep 440 question/clarification Version specifiers no "Or" available

[Nick Coghlan]

On 9 September 2016 at 13:19, Robert Collins <robertc at robertcollins.net> wrote:
> On 9 September 2016 at 15:10, Nick Coghlan <ncoghlan at gmail.com> wrote:
>> There are currently some bugs even in that, though - installing an sdist or
>> wheel directly instead of via a requirements file bypasses the environment
>> marker checks for its direct dependencies :(
>>
>> (Steve Kowalik was trying to figure that one out at the PyCon AU sprints,
>> but I don't believe he was able to track down where the missing check should
>> go)

Back on a real computer now, so the relevant bug report for that one:
https://github.com/pypa/pip/issues/3893

> I didn't mention it before but I should - its my view we should be
> really conservative about an OR in the dependency language, for the
> reasons in my earlier email.

Agreed, getting AND requirements, optional dependencies (extras), and
explicit conditional installation (environment markers) right is hard
enough without getting into the problems of full disjunctive
dependencies.

We could potentially do a better job of documenting this though - the
leap from "either A or B is fine" to having to be more explicit in
saying "in these cases, I expect A, in those cases, I expect B" isn't
always clear.

Cheers,
NIck.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia