[Python-Dev] Update on Cygwin support (was: Clarifying Cygwin support in CPython)

[Nick Coghlan]

On 26 July 2018 at 02:13, Erik Bray <erik.m.bray at gmail.com> wrote:
> I think a new approach that might be more practical for actually
> getting this platform re-supported, is to go ahead and add a CI build,
> and just skip all known failing test modules.  This is what I've done
> in a new PR to add a Cygwin build on AppVeyor:
>
> https://github.com/python/cpython/pull/8463
>
> This is far from ideal of course, and should not mean the platform is
> "supported".  But now I and others can go through and fix the
> remaining test failures, re-enable those modules in the CI
> configuration, and actually obtain some meaningful results, which will
> hopefully encourage the core committers to accept fixes for the
> platform.

I believe the PEP 538 & 540 locale handling tests are amongst those
that are still a bit sketchy (or outright broken?) on Cygwin, and I
think having an advisory CI bot would definitely help with that.
(Cygwin/MinGW are an interesting hybrid that really highlight the fact
that neither "POSIX implies not Windows" nor "Windows implies the
Win32 API" are entirely valid assumptions)

So your suggested approach seems like a plausible way forward to me.

The main potentially viable alternative I see would be to set up the
*buildbot* first, and then devote the custom builder branch to the
task of Cygwin testing for a while:
https://devguide.python.org/buildbots/#custom-builders

However, I think the overall UX of that would be worse than going down
the advisory CI path (especially since it wouldn't really help with
the aspect of parallel development introducing new Cygwin failures).

Cheers,
Nick.

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