recwarn.py 文件源码

def warns(expected_warning, *args, **kwargs):
    """Assert that code raises a particular class of warning.

    Specifically, the input @expected_warning can be a warning class or
    tuple of warning classes, and the code must return that warning
    (if a single class) or one of those warnings (if a tuple).

    This helper produces a list of ``warnings.WarningMessage`` objects,
    one for each warning raised.

    This function can be used as a context manager, or any of the other ways
    ``pytest.raises`` can be used::

        >>> with warns(RuntimeWarning):
        ...    warnings.warn("my warning", RuntimeWarning)
    """
    wcheck = WarningsChecker(expected_warning)
    if not args:
        return wcheck
    elif isinstance(args[0], str):
        code, = args
        assert isinstance(code, str)
        frame = sys._getframe(1)
        loc = frame.f_locals.copy()
        loc.update(kwargs)

        with wcheck:
            code = _pytest._code.Source(code).compile()
            py.builtin.exec_(code, frame.f_globals, loc)
    else:
        func = args[0]
        with wcheck:
            return func(*args[1:], **kwargs)