Progression is wrong when using empty string in parametrized tests

Description

Using a double decorator pytest.mark.parametrize with one of the value being "" (empty string) results in pytest not printing correctly the progress percentage.

It works:

• If there is only one decorator
• If the empty string is present only in one of the two parameter list
• If customized ids not returning an empty string are used

Environment

Environment Conda pytest 5.3.4 py36_0 python 3.6.9 h5500b2f_0

pytest and OS versions

Python 3.6.9 :: Anaconda, Inc. Windows 10 64bits pytest-5.3.4, py-1.8.1, pluggy-0.13.1

minimal example

Buggy

import pytest

@pytest.mark.parametrize("v", ["", " "])
@pytest.mark.parametrize("w", ["", " "])
def test_dummy(v, w):
    assert not v.strip()
    assert not w.strip()

pytest test_dummy.py -v
===== test session starts ===========================================
platform win32 -- Python 3.6.9, pytest-5.3.4, py-1.8.1, pluggy-0.13.1 -- python.exe
cachedir: .pytest_cache
rootdir:  
collected 4 items

test_dummy.py::test_dummy[] PASSED                               [ 25%]
test_dummy.py::test_dummy[ ] PASSED                              [ 50%]
test_dummy.py::test_dummy[ ] PASSED                              [ 50%]
test_dummy.py::test_dummy[ - ] PASSED                            [ 75%]

====== 4 passed in 0.03s ============================================

Working

import pytest

@pytest.mark.parametrize("v", ["", " "], ids=lambda a: f"'{a}'")
@pytest.mark.parametrize("w", ["", " "], ids=lambda a: f"'{a}'")
def test_dummy(v, w):
    assert not v.strip()
    assert not w.strip()

pytest test_dummy.py -v
===== test session starts ===========================================
platform win32 -- Python 3.6.9, pytest-5.3.4, py-1.8.1, pluggy-0.13.1 -- python.exe
cachedir: .pytest_cache
rootdir:  
collected 4 items

test_dummy.py::test_dummy[''-''] PASSED                                [ 25%]
test_dummy.py::test_dummy[''-' '] PASSED                               [ 50%]
test_dummy.py::test_dummy[' '-''] PASSED                               [ 75%]
test_dummy.py::test_dummy[' '-' '] PASSED                              [100%]

===== 4 passed in 0.03s ==================================================

[blueyed]

@RonnyPfannschmidt Agreed. When fixing nodeid generation in this case the test with #6599 would need to be adjusted then - or should get adjusted probably already.

[blueyed]

@bluetech I think https://github.com/pytest-dev/pytest/pull/6599 is still a valid fix for this particular issue, although the trigger has been fixed also already.

“Globally guarantee uniqueness of nodeids” is a valid issue, but should be taken out of here.