pytest plugins: deprecation warnings for renamed fixtures

[blueyed]

For pytest-django I was looking into having a prefix of "django_" for all fixtures, and adding compat warning for the old ones.

I came up with the following, but it has some issues:

• needs proper stacklevel
• is the generator test sane?

Can this be done easier?

I think it might make sense for pytest to provide some help in this regard, and there is lilkely something that I have not found..?

class PytestDjangoPrefixDeprecationWarning(DeprecationWarning):
    pass


# Copied from pytest.
def iscoroutinefunction(func):
    return getattr(func, "_is_coroutine", False) or (
        hasattr(inspect, "iscoroutinefunction") and inspect.iscoroutinefunction(func)
    )


# Copied from pytest.
def is_generator(func):
    genfunc = inspect.isgeneratorfunction(func)
    return genfunc and not iscoroutinefunction(func)


def compat_prefix_warning(new_fixture):
    # TODO: get stacklevel for warning to point at test..
    # Non-complete code via pytest-pdb:
    # https://github.com/fschulze/pytest-pdb/blob/88bb88a20c6e69ec4e3da4a2d6cabac9cfb2cd86/pytest_pdb.py#L7-L16
    # For handling fixture setup: https://github.com/fschulze/pytest-pdb/issues/7

    new_name = new_fixture.__name__
    assert new_name.startswith("django_")

    orig_func = new_fixture.__pytest_wrapped__.obj
    if is_generator(orig_func):
        @pytest.fixture
        @wraps(orig_func)
        def wrapper(**kwargs):
            msg = "Please use fixture %s instead of %s." % (new_name, new_name[7:])
            warnings.warn(PytestDjangoPrefixDeprecationWarning(msg), stacklevel=2)
            yield from orig_func(**kwargs)
    else:
        @pytest.fixture
        @wraps(orig_func)
        def wrapper(**kwargs):
            msg = "Please use fixture %s instead of %s." % (new_name, new_name[7:])
            warnings.warn(PytestDjangoPrefixDeprecationWarning(msg), stacklevel=2)
            return orig_func(**kwargs)
    return wrapper


# For backward compatibility.
settings = compat_prefix_warning(django_settings)
db = compat_prefix_warning(django_db)

[RonnyPfannschmidt]

i propose adding a usage_warning parameter to pytest.fixture ensuring it will correctly warn for all sites that request it

[blueyed]

Hmm, usage_warning would still require to wrap the old/new fixture then in some way - not sure how that would really help.

I came up with the following now:

class PytestDjangoPrefixDeprecationWarning(DeprecationWarning):
    pass


def wrap_deprecated_fixture(oldname, newname):
    @pytest.fixture(name=oldname)
    def inner(request):
        msg = "Please use fixture %s instead of %s." % (newname, oldname)
        warnings.warn(PytestDjangoPrefixDeprecationWarning(msg))
        return request.getfixturevalue(newname)
    return inner


admin_client = wrap_deprecated_fixture("admin_client", "django_admin_client")
…