[Python-Dev] Failures in test_site.py - how to debug?

[Chris Angelico]

On Sat, Aug 20, 2016 at 7:34 AM, Brett Cannon <brett at python.org> wrote:
>> 1) Demand that .pth files restrict themselves to what's already
>> imported. This means startup is still fast even if you have a bunch of
>> pths. Downside: Third-party code can break Python's rules. Upside:
>> When they do, it can be reported as a bug, the fixing of which will
>> improve startup times when that's installed.
>>
>> 2) Change the test to somehow disable .pth execution while keeping the
>> rest of site.py intact. This gives more consistent test results, but
>> still is mostly applicable to normal usage.
>>
>> 3) Ignore the problem and assume that the Python test suite will be
>> run with no site-packages installed. Status quo, basically. Possibly
>> with some tweaks so running 'make test' ignores site-packages?
>>
>> Is #2 doable?
>
>
> Anything is doable given enough time and effort. ;) As of right now the only
> way is with -S.

Heh. I guess what I really mean is: Is #2 a good idea, or would it be
considered horrendously hacky? This is my itch, so I'm not afraid to
be the one to code a solution, but I don't want to make things overall
worse to fix one specific use case.

>> If not, can 'make test' somehow hack out site-packages?
>
>
> The problem is you're dealing with startup which means it won't come into
> effect until it's too late.

Yeah, but the 'make test' operation could set an environment variable
or something to say "there are no site-packages, kthxbye". Again,
there's currently no such facility, and probably that one is a bad
idea, as it'd have implications (possibly security implications) for
other runnings of Python.

Steve's suggestion would keep all the visible hackery in test_site.py,
and it's well known that tests often need to do dark and dangerous
things.

On Sat, Aug 20, 2016 at 7:51 AM, Steve Dower <steve.dower at python.org> wrote:
>
> If you start the process with "-S", then run:
>
>     import site
>     site.addpackage = lambda *a: None
>     site.main()
>     # rest of the test
>
> Then that should do it. This will cut out all .pth processing, but shouldn't
> affect any of the other steps.

If I make a patch to do that, would it have a good chance of being accepted?

ChrisA