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

[RonnyPfannschmidt]

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

[bluetech]

@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)