suggest disabling xdist in internals guide

[dchudz]

Came up because of: #1093 (comment)

Or alternatively:

I imagine the default -n 2 in tox.ini is mostly for CI? If humans mostly want xdist disabled, I wonder about not specifying a default in tox.ini and then doing whatever we need to for CI to still have -n 2?

[DRMacIver]

I imagine the default -n 2 in tox.ini is mostly for CI? If humans mostly want xdist disabled, I wonder about not specifying a default in tox.ini and then doing whatever we need to for CI to still have -n 2?

Yeah, I think this is a good idea.

Happy to merge this as is, but would you like to change it to just doing this by default instead?

[dchudz]

would you like to change it to just doing this by default instead?

Yeah, I'll do that. (Mostly opened this PR as a place for discussion about doing that instead.)

[dchudz]

That'll also solve the problem where people don't install xdist, get the error about -n not being an option, and can't run tests. (The guide is pretty clear, but I bet it would keep happening anyway.)

[dchudz]

I'm looking into whether there's a way to have tox default to using -n 2 but not default to that running pytest directly.

If I can't find a way to do that, I think I would need to add -n 2 to all the pytest commands in tox.ini (except the ones that already do -n 0 explicitly), and also in basic-test.sh.

[alexwlchan]

@dchudz Small Internet, huh? 😉

[dchudz]

Hah, thanks @alexwlchan! (for anyone wondering, I asked the internet how to do this, and Alex came answering...: https://stackoverflow.com/questions/48856608/set-pytest-arg-for-tox-but-not-direct-pytest)

[dchudz]

Hmm, as an aside, it looks to me like setenv has to go in the [testenv] section, not the [tox] section. So unless I'm confused about its purpose, it looks to me like this bit in [tox] isn't having any effect:

setenv=
  PYTHONWARNINGS={env:PYTHONWARNINGS:error::DeprecationWarning,error::FutureWarning}

(I tried and it seems like tests currently don't object to DeprecationWarning and FutureWarning.)

[dchudz]

Just pushed the settings change to this PR. I checked that e.g. make check-fast runs with 2 xdist workers, but e.g. HYPOTHESIS_VERBOSITY_LEVEL=debug pytest tests/quality/test_shrink_quality.py -k test_minimize_multiple_elements_in_silly_large_int_range -s runs without xdist (and prints all of the stuff I'd expect).

[dchudz]

Actually I'll replace this with a new PR with a better title / branch name and without the useless commits.

[Zac-HD]

FYI the PYTHONWARNINGS bit should use the user's environment if the variable is set; but make those warnings into errors if it isn't.