issues: 545762025

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545762025 MDU6SXNzdWU1NDU3NjIwMjU= 3664 Regression 0.14.0 -> 0.14.1: __setattr__ no longer updates matching index 13662783 closed 0     2 2020-01-06T14:42:50Z 2020-01-06T16:03:16Z 2020-01-06T15:37:17Z CONTRIBUTOR      

MCVE Code Sample

This came up in the following (simplified) case: ```python import numpy as np import xarray as xr

x = [1, 2, 3, 4] data = [1., 2., 3. , 4.] dims = ["x"] coords = {"x": x} da = xr.DataArray(data, coords, dims) da1 = da.sel(x=[1, 3]) da2 = da.sel(x=[2, 4]) da2["x"].values = da1["x"].values da3 = da2 - da1 print(da3) ```

In 0.14.1, this results in an empty DataArray da3: python <xarray.DataArray (x: 0)> array([], dtype=float64) Coordinates: * x (x) int64

0.14.0 (and before), no issues: python <xarray.DataArray (x: 2)> array([1., 1.]) Coordinates: * x (x) int32 1 3

Interestingly, the values of da["x"] are okay, print(da2["x"]") gives: array([1, 3])

However, the index has not been updated, print(da2.indexes["x"]): Int64Index([2, 4], dtype='int64', name='x')

Expected Output

I'm expecting output as in 0.14.0 and before. I've briefly stepped through the code for da2["x"].values = da1["x"].values; I don't see any changes there between 0.14.0 and 0.14.1, so I'm guessing it's due to some change in the indexes. Apparently the index no longer uses the same array?

Output of xr.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.7.5 (default, Oct 31 2019, 15:18:51) [MSC v.1916 64 bit (AMD64)] python-bits: 64 OS: Windows OS-release: 10 machine: AMD64 processor: Intel64 Family 6 Model 60 Stepping 3, GenuineIntel byteorder: little LC_ALL: None LANG: en LOCALE: None.None libhdf5: 1.10.5 libnetcdf: 4.7.3 xarray: 0.14.1 pandas: 0.25.3 numpy: 1.17.3 scipy: 1.3.2 netCDF4: 1.5.3 pydap: None h5netcdf: None h5py: None Nio: None zarr: None cftime: 1.0.4.2 nc_time_axis: None PseudoNetCDF: None rasterio: 1.1.1 cfgrib: None iris: None bottleneck: None dask: 2.6.0 distributed: 2.6.0 matplotlib: 3.1.1 cartopy: None seaborn: None numbagg: None setuptools: 41.6.0.post20191030 pip: 19.3.1 conda: None pytest: None IPython: 7.9.0 sphinx: 2.2.1 
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