allow for empty output_core_dims in xr.apply_ufunc

[aha66]

• [x ] Tests added

[dcherian]

Thanks @aha66

You can get what you want by specifying exclude_dims so I am not sure this change is needed:

variable = xr.DataArray(np.arange(10), dims=["x"])


def func(a):
    return ()


xr.apply_ufunc(func, variable, input_core_dims=[["x"]], exclude_dims={"x"})

<xarray.DataArray ()>
array((), dtype=object)

A PR to improve the documentation would be very welcome.

[max-sixty]

@aha66 does @dcherian 's suggestion resolve this?

[dcherian]

@aha66 please reopen if my suggestion doesn't work for you. Thanks!