[Distutils] Finishing up PEP 517

[Nick Coghlan]

On 28 June 2017 at 13:43, Nathaniel Smith <njs at pobox.com> wrote:
> On Tue, Jun 27, 2017 at 4:20 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:
>> On 27 June 2017 at 18:54, Nathaniel Smith <njs at pobox.com> wrote:
>>> On Tue, Jun 27, 2017 at 12:27 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:
>>>> 2. If you don't find the input preparation hook:
>>>>
>>>> - call `get_build_sdist_requires()`
>>>> - call `get_build_wheel_requires()`
>>>> - install both sets of additional dependencies
>>>> - call `build_sdist()`
>>>> - unpack the sdist into the build directory
>>>> - call `build_wheel()`
>>>
>>> Side note: I think this is wrong -- I think you can't call
>>> get_build_wheel_requires until after you've unpacked the sdist,
>>> because that's a whole new tree that might be arbitrarily different.
>>> (In practice I guess this should never happen, but we should be clear
>>> conceptually I think.)
>>
>> No, both `get_build_wheel_requires()` and `build_wheel()` also have to
>> work in-place - backends aren't allowed to assume that *all* builds
>> will be out-of-tree, even though pip specifically is expected to work
>> that way. Neither of these hooks is allowed to give different results
>> depending on whether you're doing an in-place or out-of-tree build.
>
> Right. But if you're building and sdist and unpacking it and then
> calling build_wheel there, then that's not an out-of-tree build, it's
> an in-tree build in a new tree. The wheel hooks are certainly allowed
> to give different results in a VCS-tree and an unpacked-sdist-tree,
> they have different pyproject.toml files!

Umm, no. The pyproject.toml file MUST NOT change when building the
sdist. It's a human-managed input file - if any step of the build
process mutates it, that step is *broken*.

Cheers,
Nick.

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