rootpath is wrongly parsed if a path is passed as a plugin argument

[elbehery95]

The following test exposes the issue

def test_root_dir(pytester, pytestconfig) -> None:
    pytester.makeconftest(
        """
        def pytest_addoption(parser):
            # assuming a user defined plugin that requires output directory
            parser.addoption("--some-dir")"""
    )
    pytester.makepyfile(
        f"""
        def test_pass(pytestconfig):
            assert str(pytestconfig.rootpath) == r"{pytester.path}"
        """
    )
    # not passing this value or specifying it in ini addopts wont affect root dir
    result = pytester.runpytest()
    assert result.ret == 0

    # passing CLI as --<arg>=<val> wont affect root dir as well
    result = pytester.runpytest(f"--some-dir={pytester.path.parent}")
    assert result.ret == 0

    # passing CLI as --<arg> <val> affects root dir 
    result = pytester.runpytest("--some-dir", str(pytester.path.parent))
    assert result.ret == 0   # <-- test will fail here

It is really strange why supplying both --arg=val and --arg val is parsed correctly but the last one affects the root dir

[nicoddemus]

Hi @elbehery95,

Unfortunately this is a known issue: because plugins can add their own command-line options, pytest uses a feature to parse its options that sets aside "unknown options" to be processed later, and processes the known options at startup.

The problem here is that when first looking at --some-dir somepath, the command-line parser can't know beforehand if --some-dir takes a parameter or is a flag (for example, like --verbose is a flag), so the parser doesn't associate the two arguments, and pytest ends up interpreting somepath as an extra argument passed to it. When using --some-dir=somepath, there's no ambiguity because it is clear to the parser that --some-dir is taking the somepath argument.

Unfortunately we don't have a solution to this atm.