Deprecation of terminalreporter.writer causes plugin tests to fail.

[BeyondEvil]

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

[nicoddemus]

Thanks a lot @BeyondEvil!

Hmmm this is tricky, the deprecation is happening because runpytest() is registering the terminal plugin, and when it does that pytest is looking at all members of TerminalReporter to gather hooks and fixtures, which then triggers the warning when safe_getattr gets called for writer:

(Sorry for the screenshot, I'm short on time).

Not sure how to approach this, suggestions are welcome!

[BeyondEvil]

The pytest internals are very much a black box to me. But I do at least want to try and help with a solution (more of a hack maybe).

How about adding below snippet in pytester#inline_run.

        import warnings
        from _pytest.warnings import _setoption

        arg = "ignore:TerminalReporter.writer:pytest.PytestDeprecationWarning"
        _setoption(warnings, arg)

I'm happy to do a PR if there's no better solution.

[bluetech]

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.

[RonnyPfannschmidt]

Good reminder, I want that sorted soon

[ssbarnea]

@RonnyPfannschmidt I am looking forwards to see this fixed as it breaking other projects like pytest-html.

[RonnyPfannschmidt]

The Bugfix was released

[BeyondEvil]

I'm probably doing something wrong. But the error described in this issue still happens with pytest 5.4.2. @RonnyPfannschmidt

[RonnyPfannschmidt]

Then I misunderstood something and a additional fix is needed