pytest-cov is incompatible with pytest-xdist 3.x due to injection of rsync option

Summary

See pytest-dev/pytest-xdist#825 (comment) which reports a deprecation option related to rsyncdir(s) options. This breaks the builds for anyone that run with warnings-as-errors.

Code

pytest-cov/src/pytest_cov/engine.py

Line 263 in f7fced5

self.config.option.rsyncdir.append(self.cov_config)

Link to your repository, gist, pastebin or just paste raw code that illustrates the issue.

Solution

We need to stop adding this option on newer versions as it was already deprecated and will be removed on next version of xdist.

We're still seeing this DeprecationWarning being raised on the new release. What can still trigger it after the PR got merged?

We're also still getting this message.

Our workaround was to not use --cov-config and instead pass the env variable COVERAGE_RCFILE.

COVERAGE_RCFILE=.coveragerc pytest --cov

Oh damn I worded the changelog incorrectly. There's a feature test in pytest-cov for rsyncdir support. Basically the change allows pytest-cov to continute to work with xdist 4, it doesn't deal with the warning.

It's strange, because passing this env variable tells coverage to use the file I want... if we use this:

pytest -n logical --maxprocesses=4 --dist loadgroup --cov --cov-config=../configuration/.coveragerc --cov-append --cov-branch

We get this:

INTERNALERROR> DeprecationWarning: The --rsyncdir command line argument and rsyncdirs config variable are deprecated.

INTERNALERROR> The rsync feature will be removed in pytest-xdist 4.0.

This does not make sense, as we don't use rsync at all.

Doing this however:

COVERAGE_RCFILE=.coveragerc pytest -n logical --maxprocesses=4 --dist loadgroup --cov --cov-append --cov-branch

then we can run without issues and no warning.

Seems like an issue to me, can you verify please? :)

Works as expected - because you have specified the config file via pytest-cov and enabled xdist it's being sent over xdist's file sharing mechanism. It may not be what you want but it is what it's implemented.

it doesn't deal with the warning

I'm a bit confused here 😖
Is another issue needed to deal with the warning?

@ionelmc Could you help us out here?

Well I guess there could be another pytest-cov release outright removing the rsync stuff. Don't really have an opinion here. Would that make everyone happy?

I think so, if the warning is solved I think no one would complain again!
(for sure I would be super happy! 🙏)

@ionelmc, unfortunately this solution doesn't work for all: with diofant/diofant@dd326d72ad I got this build failure (problem coming from measuring coverage from sub-processes).

While removing the option completely (see skirpichev/pytest-cov@3e96ac3) does work for me, see diofant/diofant#1345 (i.e. no coverage regressions).