issues: 698577111

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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
698577111 MDU6SXNzdWU2OTg1NzcxMTE= 4417 Inconsistency in whether index is created with new dimension coordinate? 3958036 closed 0     6 2020-09-10T22:44:54Z 2022-09-13T07:54:32Z 2022-09-13T07:54:32Z CONTRIBUTOR      

It seems like set_coords() doesn't create an index variable. Is there a reason for this? I was surprised that the following code snippets produce different Datasets (first one has empty indexes, second one has x in indexes), even though both Datasets have a 'dimension coordinate' x:

(1) ``` import numpy as np import xarray as xr

ds = xr.Dataset() ds['a'] = ('x', np.linspace(0,1)) ds['b'] = ('x', np.linspace(3,4)) ds = ds.rename(b='x') ds = ds.set_coords('x')

print(ds) print('indexes', ds.indexes) ```

(2) ``` import numpy as np import xarray as xr

ds = xr.Dataset() ds['a'] = ('x', np.linspace(0,1)) ds['x'] = ('x', np.linspace(3,4))

print(ds) print('indexes', ds.indexes) ```

Environment:

Output of <tt>xr.show_versions()</tt> INSTALLED VERSIONS ------------------ commit: None python: 3.7.6 | packaged by conda-forge | (default, Jun 1 2020, 18:57:50) [GCC 7.5.0] python-bits: 64 OS: Linux OS-release: 5.4.0-47-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_GB.UTF-8 LOCALE: en_GB.UTF-8 libhdf5: 1.10.5 libnetcdf: 4.7.4 xarray: 0.16.0 pandas: 1.1.1 numpy: 1.18.5 scipy: 1.4.1 netCDF4: 1.5.3 pydap: None h5netcdf: None 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: None dask: 2.23.0 distributed: 2.25.0 matplotlib: 3.2.2 cartopy: None seaborn: None numbagg: None pint: 0.13 setuptools: 49.6.0.post20200814 pip: 20.2.3 conda: 4.8.4 pytest: 5.4.3 IPython: 7.15.0 sphinx: 3.2.1 
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