issues: 1188406993

What happened?

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

ds = xr.Dataset( {"foo": (("x", "y", "z"), np.ones((3, 4, 2)))}, {"x": ["a", "b", "c"], "y": [1, 2, 3, 4]}, ) expected = ds.sum("z") stacked = ds.stack(space=["x", "y"])

broadcasted, _ = xr.broadcast(stacked, stacked.space)

stacked.sum("z").unstack("space") # works broadcasted.sum("z").unstack("space") # error ```

```

ValueError Traceback (most recent call last) Input In [13], in <module> 10 broadcasted, _ = xr.broadcast(stacked, stacked.space) 11 stacked.sum("z").unstack("space") ---> 12 broadcasted.sum("z").unstack("space")

File ~/work/python/xarray/xarray/core/dataset.py:4332, in Dataset.unstack(self, dim, fill_value, sparse) 4330 non_multi_dims = set(dims) - set(stacked_indexes) 4331 if non_multi_dims: -> 4332 raise ValueError( 4333 "cannot unstack dimensions that do not " 4334 f"have exactly one multi-index: {tuple(non_multi_dims)}" 4335 ) 4337 result = self.copy(deep=False) 4339 # we want to avoid allocating an object-dtype ndarray for a MultiIndex, 4340 # so we can't just access self.variables[v].data for every variable. 4341 # We only check the non-index variables. 4342 # https://github.com/pydata/xarray/issues/5902

ValueError: cannot unstack dimensions that do not have exactly one multi-index: ('space',) ```

What did you expect to happen?

This should work.

Minimal Complete Verifiable Example

No response

Relevant log output

No response

Anything else we need to know?

No response

Environment

xarray main after the flexible indexes refactor