StopIteration error in CircleCI using split tests pattern

[Morendil]

These lines in release 3.10.0:

pytest/src/_pytest/main.py

Lines 550 to 551 in 5ac4eff

	if argpath.basename == "__init__.py":
	yield next(m[0].collect())

…are causing a regression when running tests under CircleCI (with the Python 3.7 image) with the recommended split test pattern and globbing:

pytest `circleci tests glob "tests/**/*.py" | circleci tests split`

(We are not seeing the same failure in Python 2 builds.)

A minimal reproduction consists simply of:

touch __init__.py
pytest __init__.py

============================================================================================================ test session starts =============================================================================================================
platform linux -- Python 3.7.0, pytest-3.10.0, py-1.7.0, pluggy-0.8.0
rootdir: /app, inifile: setup.cfg
collected 0 items / 1 errors

=================================================================================================================== ERRORS ===================================================================================================================
_____________________________________________________________________________________________________________ ERROR collecting  ______________________________________________________________________________________________________________
/usr/local/lib/python3.7/site-packages/_pytest/main.py:568: in _collect
    yield next(m[0].collect())
E   StopIteration

The above exception was the direct cause of the following exception:
/usr/local/lib/python3.7/site-packages/_pytest/runner.py:212: in __init__
    self.result = func()
/usr/local/lib/python3.7/site-packages/_pytest/runner.py:272: in <lambda>
    call = CallInfo(lambda: list(collector.collect()), "collect")
/usr/local/lib/python3.7/site-packages/_pytest/main.py:478: in collect
    for x in self._collect(arg):
E   RuntimeError: generator raised StopIteration
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
========================================================================================================== 1 error in 0.30 seconds ===========================================================================================================

Our pip list is simply a fresh install of PyTest:

Package        Version
-------------- -------
atomicwrites   1.2.1
attrs          18.2.0
more-itertools 4.3.0
pip            18.0
pluggy         0.8.0
py             1.7.0
pytest         3.10.0
setuptools     40.0.0
six            1.11.0
wheel          0.31.1

• Include a detailed description of the bug or suggestion
• pip list of the virtual environment you are using
• pytest and operating system versions
• Minimal example if possible

[blueyed]

Caused by 5ac4eff.
/cc @kchmck

[blueyed]

Please note: there have been other fixes with regard to collection already (in master), which might help, but we should clearly have a test for this.

[blueyed]

Just for reference, here is a failing test for when I looked into this a while ago:

def test_collect_pkg_init(testdir):
    subdir = testdir.mkdir("sub")
    init = subdir.ensure("__init__.py")
    init.write("def test_init(): pass")
    p = subdir.ensure("test_file.py")
    p.write("def test_file(): pass")

    # https://github.com/pytest-dev/pytest/issues/4344
    result = testdir.runpytest(str(init), str(p))
    result.stdout.fnmatch_lines(["*2 passed in*"])

[webknjaz]

Ah.. I was about to submit the same bug :)

Ref: cherrypy/cheroot#146 (comment)

[blueyed]

The above failing test does not trigger the StopIteration, but is likely still related.

It starts to fail with fa35f65:

commit fa35f650b53821baa85c78caf116fd9e4522c408
Date:   Tue Nov 6 18:47:19 2018 +0100

    Fix handling of duplicate args with regard to Python packages

    Fixes https://github.com/pytest-dev/pytest/issues/4310.