issues: 683657289

Indexing a datetime64[ns] coordinate with a scalar datetime.date produces a KeyError ([6]). Curiously, indexing with a datetime.date slice does work ([5]). I would expect [6] to work just like [4].

This may well be related to (or a duplicate of) #3736, #4283, #4292, #4306, #4319, or #4370, but none of those actually mentions datetime.date objects, so I can't tell.

```python In [1]: import xarray as xr, pandas as pd, datetime as dt

In [2]: x = xr.DataArray([1., 2., 3.], [('foo', pd.date_range('2010-01-01', periods=3))])

In [3]: x Out[3]: <xarray.DataArray (foo: 3)> array([1., 2., 3.]) Coordinates: * foo (foo) datetime64[ns] 2010-01-01 2010-01-02 2010-01-03

In [4]: x.loc[dt.datetime(2010, 1, 1)] Out[4]: <xarray.DataArray ()> array(1.) Coordinates: foo datetime64[ns] 2010-01-01

In [5]: x.loc[dt.date(2010, 1, 1):dt.date(2010, 1, 3)] Out[5]: <xarray.DataArray (foo: 3)> array([1., 2., 3.]) Coordinates: * foo (foo) datetime64[ns] 2010-01-01 2010-01-02 2010-01-03

In [6]: x.loc[dt.date(2010, 1, 1)]

KeyError Traceback (most recent call last) <ipython-input-5-8ef314626f7d> in <module> ----> 1 x.loc[dt.date(2010, 1, 1)]

~/.conda/envs/build/lib/python3.7/site-packages/xarray/core/dataarray.py in getitem(self, key) 196 labels = indexing.expanded_indexer(key, self.data_array.ndim) 197 key = dict(zip(self.data_array.dims, labels)) --> 198 return self.data_array.sel(**key) 199 200 def setitem(self, key, value) -> None:

~/.conda/envs/build/lib/python3.7/site-packages/xarray/core/dataarray.py in sel(self, indexers, method, tolerance, drop, indexers_kwargs) 1152 method=method, 1153 tolerance=tolerance, -> 1154 indexers_kwargs, 1155 ) 1156 return self._from_temp_dataset(ds)

~/.conda/envs/build/lib/python3.7/site-packages/xarray/core/dataset.py in sel(self, indexers, method, tolerance, drop, **indexers_kwargs) 2100 indexers = either_dict_or_kwargs(indexers, indexers_kwargs, "sel") 2101 pos_indexers, new_indexes = remap_label_indexers( -> 2102 self, indexers=indexers, method=method, tolerance=tolerance 2103 ) 2104 result = self.isel(indexers=pos_indexers, drop=drop)

~/.conda/envs/build/lib/python3.7/site-packages/xarray/core/coordinates.py in remap_label_indexers(obj, indexers, method, tolerance, **indexers_kwargs) 395 396 pos_indexers, new_indexes = indexing.remap_label_indexers( --> 397 obj, v_indexers, method=method, tolerance=tolerance 398 ) 399 # attach indexer's coordinate to pos_indexers

~/.conda/envs/build/lib/python3.7/site-packages/xarray/core/indexing.py in remap_label_indexers(data_obj, indexers, method, tolerance) 268 coords_dtype = data_obj.coords[dim].dtype 269 label = maybe_cast_to_coords_dtype(label, coords_dtype) --> 270 idxr, new_idx = convert_label_indexer(index, label, dim, method, tolerance) 271 pos_indexers[dim] = idxr 272 if new_idx is not None:

~/.conda/envs/build/lib/python3.7/site-packages/xarray/core/indexing.py in convert_label_indexer(index, label, index_name, method, tolerance) 188 else: 189 indexer = index.get_loc( --> 190 label.item(), method=method, tolerance=tolerance 191 ) 192 elif label.dtype.kind == "b":

~/.conda/envs/build/lib/python3.7/site-packages/pandas/core/indexes/datetimes.py in get_loc(self, key, method, tolerance) 620 else: 621 # unrecognized type --> 622 raise KeyError(key) 623 624 try:

KeyError: datetime.date(2010, 1, 1) ```

Environment:

Output of <tt>xr.show_versions()</tt>

INSTALLED VERSIONS ------------------ commit: None python: 3.7.8 | packaged by conda-forge | (default, Jul 31 2020, 02:25:08) [GCC 7.5.0] python-bits: 64 OS: Linux OS-release: 3.10.0-693.el7.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 libhdf5: 1.10.6 libnetcdf: 4.7.4 xarray: 0.16.0 pandas: 1.1.0 numpy: 1.19.1 scipy: 1.5.2 netCDF4: 1.5.4 pydap: None h5netcdf: 0.8.1 h5py: 2.10.0 Nio: None zarr: None cftime: 1.2.1 nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: 1.3.2 dask: 2.23.0 distributed: 2.23.0 matplotlib: 3.3.1 cartopy: None seaborn: 0.10.1 numbagg: installed pint: None setuptools: 49.6.0.post20200814 pip: 20.2.2 conda: 4.8.4 pytest: None IPython: 7.17.0 sphinx: None