[Distutils] setup_requires for dev environments

[Daniel Holth]

Robert: is it a requirement to you that "python setup.py ..." should
install setup_requires? For me I'd be quite happy if installing the
requirements was my own problem in the absence of an installer.

I would like to start writing my setup.py like this:

setup.cfg:
setup-requires = waf

setup.py:
import waf
interpret setup.py arguments
build with waf
don't import setuptools


On Mon, Mar 16, 2015 at 7:39 PM, Robert Collins
<robertc at robertcollins.net> wrote:
> On 17 March 2015 at 12:32, Donald Stufft <donald at stufft.io> wrote:
>>
>> On Mar 16, 2015, at 7:03 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
>>
>>
>> On 17 Mar 2015 02:33, "Daniel Holth" <dholth at gmail.com> wrote:
>>>
>>> Problem: Users would like to be able to import stuff in setup.py. This
>>> could be anything from a version fetcher to a replacement for
>>> distutils itself. However, if setup.py is the only place to specify
>>> these requirements there's a bit of a chicken and egg problem, unless
>>> they have unusually good setuptools knowledge, especially if you want
>>> to replace the  entire setup() implementation.
>>>
>>> Problem: Having easy_install do it is not what people want and misses
>>> some important use cases.
>>>
>>> Problem: Based on empirical evidence PEP 426 will never be done. Its
>>> current purpose is to shut down discussion of pragmatic solutions.
>>
>> Slight correction here: one of my current aims with PEP 426 is deliberately
>> discouraging the discussion of solutions that only work reliably if everyone
>> switches to a new build system first. That's a) never going to happen; and
>> b) one of the key mistakes the distutils2 folks made that significantly
>> hindered adoption of their work, and I don't want us to repeat it.
>>
>> My other key aim is to provide a public definition of what I think "good"
>> looks like when it comes to software distribution, so I can more easily
>> assess whether less radical proposals are still moving us closer to that
>> goal.
>>
>> Making pip (and perhaps easy_install) setup.cfg aware, such that it assumes
>> the use of d2to1 (or a semantically equivalent tool) if setup.cfg is present
>> and hence is able to skip invoking setup.py in relevant cases, sounds like
>> just such a positive incremental step to me, as it increases the number of
>> situations where pip can avoid executing a Turing complete "configuration"
>> file, without impeding the eventual adoption of a more comprehensive
>> solution.
>>
>> I don't think that needs a PEP - just an RFE against pip to make it d2to1
>> aware for each use case where it's relevant, like installing setup.py
>> dependencies. (And perhaps a similar RFE against setuptools)
>>
>> Projects that choose to rely on that new feature will be setting a high
>> minimum installer version for their users, but some projects will be OK with
>> that (especially projects private to a single organisation after upgrading
>> pip on their production systems).
>>
>> Cheers,
>> Nick.
>>
>>
>>
>> I don’t think that’s going to work, because if you only make pip aware of it
>> then you break ``python setup.py sdist``, if you make setuptools aware of it
>> then you don’t need pip to be aware of it because we’ll get it for free from
>> setuptools being aware of it.
>
> Huh?
>
> I think the key tests are:
>  - what happens with old tools
>  - what happens with new tools
>
> With old tools it needs to not-break.
> With new tools it should be better :).
>
> Teaching pip, double-entered setup_requires (.cfg and .py).
>  old tools keep working
>  new tools are shiny (pip install -e / vcs then setup's easy_install
> call short-circuits doing nothing).
>
> Teaching only setuptools, double-entered
>  old tools keep working
>  new tools are not shiny, because pip isn't doing the install
>
> Teaching only setuptools, single entry
>  old tools break (requirements absent, or you have a versioned dep on
> setuptools in setup.py and omg the pain)
>  new tools are not shiny, same reason
>
> Teaching setuptools and pip, single entry
>  old tools break - as above
>  new tools are shiny (because pip either asks setuptools or reads
> setup.cfg, whatever)
>
> So I think we must teach pip, and we may teach setuptools.
>
> -Rob
>
> --
> Robert Collins <rbtcollins at hp.com>
> Distinguished Technologist
> HP Converged Cloud
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