issue_comments: 527684331

After digging a little bit more, I think the reason why filterwarnings() made me think the indexing tests pass is that when a UnitStrippedWarning is raised (mostly after accessing __array_struct__), the filter replaces it with a DimensionalityError, complaining that it can't convert to dimensionless. This confuses me: when directly accessing an attribute starting with __array_, pytest correctly points out the raised UnitStrippedWarning.

Also, it seems that because DimensionalityError inherits from ValueError, the type of the parameter index of convert_label_indexer is changed from Int64Index to Index (which has dtype="object" ), which does not cast to ndarray, thus keeping the unit information and causing sel() to correctly raise a KeyError. I can reproduce both behaviors using ```python import numpy as np import pytest import xarray as xr

pint = pytest.importorskip("pint") ureg = pint.UnitRegistry()

@pytest.mark.xfail def test_indexing_fail(): array = np.linspace(1, 2, 20) * ureg.m x = np.arange(len(array)) * ureg.s data_array = xr.DataArray(data=array, coords={"x": x}, dims=["x"]) with pytest.raises(KeyError): data_array.sel(x=np.array([13, 5, 9]) * ureg.m)

@pytest.mark.filterwarnings("error:::pint[.*]") def test_indexing_pass(): array = np.linspace(1, 2, 20) * ureg.m x = np.arange(len(array)) * ureg.s data_array = xr.DataArray(data=array, coords={"x": x}, dims=["x"]) with pytest.raises(KeyError): data_array.sel(x=np.array([13, 5, 9]) * ureg.m) ``` Note: the only difference between the two is the decorator.