pytest: Deprecation of terminalreporter.writer causes plugin tests to fail.

After the deprecation of terminalreporter.writer pytest plugin tests using pytester are getting the deprecation warning, even tho the plugin is not using terminalreporter at all.

Using pytest version 5.3.5 it works as expected.

Tested on both Linux and Mac using the below example test.

pytest_plugins = ("pytester",)

def test_base(testdir, recwarn):
    testdir.makepyfile("def test_pass(): pass")
    testdir.runpytest()
    print(recwarn.list[0])
    assert len(recwarn) == 0
    assert True

test outcome

# pytest -s -ra -v
=========================================================================================== test session starts ============================================================================================
platform linux -- Python 3.7.6, pytest-5.4.1, py-1.8.1, pluggy-0.13.1 -- /usr/local/bin/python
cachedir: .pytest_cache
rootdir: /pytest-dev/pytest-playground/tests, inifile: pytest.ini
collected 1 item                                                                                                                                                                                           

test_selenium.py::test_base =========================================================================================== test session starts ============================================================================================
platform linux -- Python 3.7.6, pytest-5.4.1, py-1.8.1, pluggy-0.13.1
rootdir: /tmp/pytest-of-root/pytest-5/test_base0
collected 1 item

test_base.py .                                                                                                                                                                                       [100%]

============================================================================================ 1 passed in 0.01s =============================================================================================
{message : PytestDeprecationWarning('TerminalReporter.writer attribute is deprecated, use TerminalReporter._tw instead at your own risk.\nSee https://docs.pytest.org/en/latest/deprecations.html#terminalreporter-writer for more information.'), category : 'PytestDeprecationWarning', filename : '/usr/local/lib/python3.7/site-packages/_pytest/terminal.py', lineno : 289, line : None}
FAILED

================================================================================================= FAILURES =================================================================================================
________________________________________________________________________________________________ test_base _________________________________________________________________________________________________

testdir = <Testdir local('/tmp/pytest-of-root/pytest-5/test_base0')>, recwarn = WarningsRecorder(record=True)

    def test_base(testdir, recwarn):
        testdir.makepyfile("def test_pass(): pass")
        testdir.runpytest()
        print(recwarn.list[0])
>       assert len(recwarn) == 0
E       assert 1 == 0
E         +1
E         -0

/pytest-dev/pytest-playground/tests/test_selenium.py:10: AssertionError
========================================================================================= short test summary info ==========================================================================================
FAILED test_selenium.py::test_base - assert 1 == 0
============================================================================================ 1 failed in 0.18s =============================================================================================

I’m seeing tests fail in pytest-html which only uses terminalreporter.write_sep() in a hook, and in pytest-variables which does not use terminalreporter at all.

It’s failing for both python 3.6 and 3.7. Example

About this issue

Original URL
State: closed
Created 4 years ago
Reactions: 8
Comments: 26 (18 by maintainers)

Commits related to this issue

pin pytest to range pin pytes to range until we deal with this: https://github.com/pytest-dev/pytest/issues/6936 — committed to broadinstitute/viral-core by tomkinsc 4 years ago
Remove nonrelevant deprecation warning during tests See https://github.com/pytest-dev/pytest/issues/6936 — committed to pytest-dev/pytest-describe by Cito 3 years ago

Most upvoted comments

I’m going to try and get to it this evening

RonnyPfannschmidt on Jun 9, 2020

@BeyondEvil it isn’t merged yet, unless I misunderstand.

For reference, the issue is this:

TerminalReporter has an property writer that has been deprecated in pytest 5.4.0. So every time it is accessed, a deprecation warning is triggered.

TerminalReporer is a plugin. A plugin can define fixtures. During the collection phase, pytest collects fixtures by sifting through all attributes of an object (plugin in this case), accessing them with getattr and checking if they are fixtures. If the attribute is a property, its actually runs, and in writers case triggers the warning.

What @RonnyPfannschmidt’s change does is: before probing a given attribute, check if it is a property, and if so, skip it. The change itself is small and can be extracted to its own PR. But before we do so, we should check:

Is there some reasonable possibility/use-case for using a property to define a fixture? (probably not)
Does the fix adversely impact performance? (probably not)

bluetech on May 17, 2020

I was about to remove this for 6.0, but then thought it was better to just wait to remove this in 6.1: I don’t see much reason to bypass our usual deprecation/removal process.

nicoddemus on Jul 16, 2020

Is there some reasonable possibility/use-case for using a property define a fixture? (probably not)

I agree, but with tongue-in-cheek, I’m sure there’s a test suite out there which has a property, that when accessed, returns a function marked as a fixture. 😆

nicoddemus on May 17, 2020

Atm anything, currently I don’t have much time for pytest due to global reasons

RonnyPfannschmidt on May 14, 2020

Good reminder, I want that sorted soon

RonnyPfannschmidt on May 10, 2020

This will be fixed by #6898, which includes a change to skip the getattr on properties. Not sure what @RonnyPfannschmidt’s plan is for that PR.

bluetech on May 10, 2020