pytest fails with implicit namespaces

[aatkinson]

Pytest doesn't seem to work with implicit namespaces in your source, as defined by PEP 420. This still occurs as of pytest 5.0.1 installed in a Python 3 environment.

Note this is for the source package being tested, and I've encountered the issue with tests outside of the source package (init.py files are required for tests as noted in the best practices document.

E.g.

mypkg/
    foo/
        baz.py
    bar/
        baz.py
tests/

will yield errors like

./../../.local/lib/python3.6/site-packages/py/_path/local.py:721: in pyimport
    raise self.ImportMismatchError(modname, modfile, self)
E   py._path.local.LocalPath.ImportMismatchError: ('baz', '/home/vsts/work/1/s/mkpkg/foo/baz.py', local('/home/vsts/work/1/s/mkpkg/bar/mkpkg.py'))

This issue has appeared in #774.

[asottile]

I cannot reproduce, did you cp -r the foo and bar directories?

$ find mypkg/ tests -name '*.py' | xargs tail -n999
==> mypkg/bar/baz.py <==

==> mypkg/foo/baz.py <==

==> tests/test_foo.py <==
import mypkg.foo.baz
import mypkg.bar.baz


def test(): pass

$ python -m pytest tests
============================= test session starts ==============================
platform linux -- Python 3.6.8, pytest-5.0.1, py-1.8.0, pluggy-0.12.0
rootdir: /tmp/x
collected 1 item                                                               

tests/test_foo.py .                                                      [100%]

=========================== 1 passed in 0.01 seconds ===========================

[Zac-HD]

Closing as stale; I can't reproduce it either (and #774 was test files, not code files).