Ignore spurious ResourceWarning in tests when opening the rendered result in the browser on Linux

[martinRenou]

This prevents the tests from failing when running them with the --open-browser option. As discussed in #33 (comment)

[CAM-Gerlach]

(Somehow, my first review didn't get picked up correctly, sorry)

[CAM-Gerlach]

The issue with this very broad brush approach is it also silences any ResourceWarning anywhere in the code under test (or the test suite), and regardless of whether `--open-browser`` is passed. Instead, what I recommend you do is

You can add the warnings filter to _open_browser in the open_browser fixture in conftest.py.

as this will ensure that it is only activated when it is needed (unless you can't get that to work, in which case there are still other less drastic options) Further, you should limit the filter to just the subprocess module (fourth field in the filter syntax, right after category).

Thanks!

Furthermore, I'd suggest limiting the filter to the subprocess module

[martinRenou]

Thanks for the review.

You can add the warnings filter to _open_browser in the open_browser fixture in conftest.py.

I fail to understand how this would look like? I tried multiple things, like:

@pytest.fixture
def open_browser(request):
    """Show the passed URL in the user's web browser if passed."""
    def _open_browser(url):
        if request.config.getoption(OPEN_BROWSER_OPTION):
            pytestmark = pytest.mark.filterwarnings("ignore::ResourceWarning")

            webbrowser.open_new_tab(url)
    return _open_browser

Or

@pytest.fixture
def open_browser(request):
    """Show the passed URL in the user's web browser if passed."""
    @pytest.mark.filterwarnings("ignore::ResourceWarning")
    def _open_browser(url):
        if request.config.getoption(OPEN_BROWSER_OPTION):
            webbrowser.open_new_tab(url)
    return _open_browser

But that does not work. I didn't find any documentation about filtering warnings on pytest fixtures, it seems to only be documented for test cases.

[CAM-Gerlach]

Sorry, I meant just using the normal warnings.filterwarnings, i.e.

@pytest.fixture
def open_browser(request):
    """Show the passed URL in the user's web browser if passed."""
    def _open_browser(url):
        if request.config.getoption(OPEN_BROWSER_OPTION):
            warnings.filterwarnings(
                'ignore', category=ResourceWarning, module='subprocess.*')
            webbrowser.open_new_tab(url)
    return _open_browser

(You might need to play around with the module option; if you can't get it to work at all, you can elide it if nessesary)

This ensures it works regardless of where/what scope the warning fires at (which can be tricky due to relating to non-deterministic, OS-specific source/destructor behavior, as suggested by the nature of the warning and the traceback), and gets applied immediately before opening the browser, if and only if the browser is to be opened (and without having to add it directly to any test code that uses it).

[martinRenou]

Oh I see, thanks!

I updated the PR

[CAM-Gerlach]

LGTM, thanks @martinRenou !