issues: 340733448

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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
340733448 MDU6SXNzdWUzNDA3MzM0NDg= 2283 Exact alignment should allow missing dimension coordinates 1217238 open 0     2 2018-07-12T17:40:24Z 2021-06-15T09:52:29Z   MEMBER      

Code Sample, a copy-pastable example if possible

python import xarray as xr xr.align(xr.DataArray([1, 2, 3], dims='x'), xr.DataArray([1, 2, 3], dims='x', coords=[[0, 1, 2]]), join='exact')

Problem description

This currently results in an error, but a missing index of size 3 does not actually conflict: ```python-traceback

ValueError Traceback (most recent call last) <ipython-input-15-1d63d3512fb6> in <module>() 1 xr.align(xr.DataArray([1, 2, 3], dims='x'), 2 xr.DataArray([1, 2, 3], dims='x', coords=[[0, 1, 2]]), ----> 3 join='exact')

/usr/local/lib/python3.6/dist-packages/xarray/core/alignment.py in align(objects, *kwargs) 129 raise ValueError( 130 'indexes along dimension {!r} are not equal' --> 131 .format(dim)) 132 index = joiner(matching_indexes) 133 joined_indexes[dim] = index

ValueError: indexes along dimension 'x' are not equal ```

This surfaced as an issue on StackOverflow: https://stackoverflow.com/questions/51308962/computing-matrix-vector-multiplication-for-each-time-point-in-two-dataarrays

Expected Output

Both output arrays should end up with the x coordinate from the input that has it, like the output of the above expression if join='inner': (<xarray.DataArray (x: 3)> array([1, 2, 3]) Coordinates: * x (x) int64 0 1 2, <xarray.DataArray (x: 3)> array([1, 2, 3]) Coordinates: * x (x) int64 0 1 2)

Output of xr.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.6.3.final.0 python-bits: 64 OS: Linux OS-release: 4.14.33+ machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 xarray: 0.10.7 pandas: 0.22.0 numpy: 1.14.5 scipy: 0.19.1 netCDF4: None h5netcdf: None h5py: 2.8.0 Nio: None zarr: None bottleneck: None cyordereddict: None dask: None distributed: None matplotlib: 2.1.2 cartopy: None seaborn: 0.7.1 setuptools: 39.1.0 pip: 10.0.1 conda: None pytest: None IPython: 5.5.0 sphinx: None 
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     13221727 issue

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