id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1207399616,PR_kwDOAMm_X842YT9J,6501,HTML repr fix for Furo Sphinx theme,11411331,closed,0,,,4,2022-04-18T20:03:01Z,2022-04-18T21:05:43Z,2022-04-18T20:53:43Z,CONTRIBUTOR,,0,pydata/xarray/pulls/6501,"<!-- Feel free to remove check-list items aren't relevant to your change -->

- [x] Closes #6500
- [x] User visible changes (including notable bug fixes) are documented in `whats-new.rst`","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6501/reactions"", ""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
630573329,MDU6SXNzdWU2MzA1NzMzMjk=,4121,decode_cf doesn't work for ancillary_variables in attributes,30388627,closed,0,,,4,2020-06-04T07:18:34Z,2022-04-18T15:56:22Z,2022-04-18T15:56:22Z,NONE,,,,"<!-- A short summary of the issue, if appropriate -->
Sometimes we have one attribute called `ancillary_variables` which is a list containing several strings. It would be useful to decode them.

#### MCVE Code Sample

```python
import numpy as np
import xarray as xr
import pandas as pd

temp = 15 + 8 * np.random.randn(2, 2, 3)
precip = 10 * np.random.rand(2, 2, 3)

temp = xr.DataArray(temp, dims=['x', 'y', 'time'])
precip = xr.DataArray(precip, dims=['x', 'y', 'time'])

lon = [[-99.83, -99.32], [-99.79, -99.23]]
lat = [[42.25, 42.21], [42.63, 42.59]]

temp.attrs['ancillary_variables'] = ['precip']
precip.attrs['ancillary_variables'] = ['temp']

ds = xr.Dataset({'temperature': temp,
                 'precipitation': precip},
                 coords={'lon': (['x', 'y'], lon),
                         'lat': (['x', 'y'], lat),
                         'time': pd.date_range('2014-09-06', periods=3),
                         'reference_time': pd.Timestamp('2014-09-05')})

ds.to_netcdf('test_ancillary_variables.nc', engine='netcdf4')

ds_new = xr.open_dataset('test_ancillary_variables.nc', decode_cf=True)
print(ds_new['temperature'])
```

#### Expected Output
```
......
Attributes:
    ancillary_variables:  [<xarray.DataArray (x: 2, y: 2, time: 3)> ......... ]
```

#### Versions

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

<!-- Paste the output here xr.show_versions() here -->
INSTALLED VERSIONS
------------------
commit: None
python: 3.7.6 | packaged by conda-forge | (default, Mar 23 2020, 23:03:20) 
[GCC 7.3.0]
python-bits: 64
OS: Linux
OS-release: 4.9.0-8-amd64
machine: x86_64
processor: 
byteorder: little
LC_ALL: None
LANG: en_US.utf8
LOCALE: en_US.UTF-8
libhdf5: 1.10.5
libnetcdf: 4.7.4

xarray: 0.15.1
pandas: 1.0.4
numpy: 1.18.4
scipy: 1.4.1
netCDF4: 1.5.3
pydap: None
h5netcdf: None
h5py: 2.10.0
Nio: None
zarr: 2.4.0
cftime: 1.1.3
nc_time_axis: None
PseudoNetCDF: None
rasterio: 1.1.5
cfgrib: None
iris: None
bottleneck: None
dask: 2.14.0
distributed: 2.17.0
matplotlib: 3.2.1
cartopy: 0.18.0
seaborn: None
numbagg: None
setuptools: 47.1.1.post20200529
pip: 20.1.1
conda: None
pytest: None
IPython: None
sphinx: None

</details>
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4121/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
474463902,MDU6SXNzdWU0NzQ0NjM5MDI=,3169,Plotting inconsistencies with Cartopy,358378,closed,0,,,4,2019-07-30T09:06:15Z,2022-04-18T15:49:12Z,2022-04-18T15:49:12Z,CONTRIBUTOR,,,,"I'm on xarray 0.11.3, and currently do not have the possibility to test on master.  However, the commit history suggests that this issue still exists.  Please accept my apologies if I missed something.

I'm following the plotting documentation at https://xarray.pydata.org/en/stable/plotting.html#maps

When plotting two maps in the same call (exactly as written in the documentation),

    p = air.isel(time=[0, 1]).plot(transform=ccrs.PlateCarree(), col='time',
                                   subplot_kws={'projection': ccrs.Orthographic(-80, 35)})
    
    for ax in p.axes.flat:
        ax.coastlines()
        ax.gridlines()

everything works fine.

However, when I only want to plot one map,

    p = air.isel(time=[0]).plot(transform=ccrs.PlateCarree(),
                                subplot_kws={'projection': ccrs.Orthographic(-80, 35)})
    
    for ax in p.axes.flat:
        ax.coastlines()
        ax.gridlines()

I get the following error:

    ---------------------------------------------------------------------------
    ValueError                                Traceback (most recent call last)
    <ipython-input-63-2c5a2a533878> in <module>
          1 p = air.isel(time=[0]).plot(transform=ccrs.PlateCarree(),
    ----> 2                             subplot_kws={'projection': ccrs.Orthographic(-80, 35)})
          3 
          4 for ax in p.axes.flat:
          5     ax.coastlines()
    
    /home/jupyterhub/conda/envs/prod/lib/python3.6/site-packages/xarray/plot/plot.py in __call__(self, **kwargs)
        550 
        551     def __call__(self, **kwargs):
    --> 552         return plot(self._da, **kwargs)
        553 
        554     @functools.wraps(hist)
    
    /home/jupyterhub/conda/envs/prod/lib/python3.6/site-packages/xarray/plot/plot.py in plot(darray, row, col, col_wrap, ax, hue, rtol, subplot_kws, **kwargs)
        185     kwargs['ax'] = ax
        186 
    --> 187     return plotfunc(darray, **kwargs)
        188 
        189 
    
    /home/jupyterhub/conda/envs/prod/lib/python3.6/site-packages/xarray/plot/plot.py in newplotfunc(darray, x, y, figsize, size, aspect, ax, row, col, col_wrap, xincrease, yincrease, add_colorbar, add_labels, vmin, vmax, cmap, center, robust, extend, levels, infer_intervals, colors, subplot_kws, cbar_ax, cbar_kwargs, xscale, yscale, xticks, yticks, xlim, ylim, norm, **kwargs)
        852                              vmax=cmap_params['vmax'],
        853                              norm=cmap_params['norm'],
    --> 854                              **kwargs)
        855 
        856         # Label the plot with metadata
    
    /home/jupyterhub/conda/envs/prod/lib/python3.6/site-packages/xarray/plot/plot.py in pcolormesh(x, y, z, ax, infer_intervals, **kwargs)
       1106             y = _infer_interval_breaks(y, axis=0)
       1107 
    -> 1108     primitive = ax.pcolormesh(x, y, z, **kwargs)
       1109 
       1110     # by default, pcolormesh picks ""round"" values for bounds
    
    /home/jupyterhub/conda/envs/prod/lib/python3.6/site-packages/matplotlib/__init__.py in inner(ax, data, *args, **kwargs)
       1808                         ""the Matplotlib list!)"" % (label_namer, func.__name__),
       1809                         RuntimeWarning, stacklevel=2)
    -> 1810             return func(ax, *args, **kwargs)
       1811 
       1812         inner.__doc__ = _add_data_doc(inner.__doc__,
    
    /home/jupyterhub/conda/envs/prod/lib/python3.6/site-packages/matplotlib/axes/_axes.py in pcolormesh(self, alpha, norm, cmap, vmin, vmax, shading, antialiased, *args, **kwargs)
       6011         if (not isinstance(t, mtransforms.Transform) and
       6012             hasattr(t, '_as_mpl_transform')):
    -> 6013             t = t._as_mpl_transform(self.axes)
       6014 
       6015         if t and any(t.contains_branch_seperately(self.transData)):
    
    lib/cartopy/_crs.pyx in cartopy._crs.CRS._as_mpl_transform()
    
    ValueError: Axes should be an instance of GeoAxes, got <class 'matplotlib.axes._subplots.AxesSubplot'>

It is not clear (from the user perspective) why one should work and the other should not.

Of course I can create the axes instance before using xarray's `plot` function, but it would be nicer if I wouldn't have to.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3169/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
309686915,MDU6SXNzdWUzMDk2ODY5MTU=,2027,square-bracket slice a Dataset with a DataArray,6213168,open,0,,,4,2018-03-29T09:39:57Z,2022-04-18T03:51:25Z,,MEMBER,,,,"Given this:
```
ds = xarray.Dataset(
    data_vars={
        'vote': ('pupil', [5, 7, 8]),
        'age': ('pupil', [15, 14, 16])
    },
    coords={
        'pupil': ['Alice', 'Bob', 'Charlie']
    })


<xarray.Dataset>
Dimensions:  (pupil: 3)
Coordinates:
  * pupil    (pupil) <U7 'Alice' 'Bob' 'Charlie'
Data variables:
    vote     (pupil) int64 5 7 8
    age      (pupil) int64 15 14 16
```

Why does this work:
```
ds.age[ds.vote >= 6]

<xarray.DataArray 'age' (pupil: 2)>
array([14, 16])
Coordinates:
  * pupil    (pupil) <U7 'Bob' 'Charlie'
```

But this doesn't?
```
ds[ds.vote >= 6]

KeyError: False
```
``ds.vote >= 6`` is a DataArray with dims=('pupil', ) and dtype=bool, so I can't think of any ambiguity in what I want to achieve?

Workaround:
```
ds.sel(pupil=ds.vote >= 6)


<xarray.Dataset>
Dimensions:  (pupil: 2)
Coordinates:
  * pupil    (pupil) <U7 'Bob' 'Charlie'
Data variables:
    vote     (pupil) int64 7 8
    age      (pupil) int64 14 16
```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2027/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue