xarray: dask compute on reduction failes with ValueError

I’m doing a reduction like mean on a dask-backed DataArray, and passing it to dask.compute

In [3]: from dask import compute
   ...: import numpy as np
   ...: import xarray as xr
   ...:

In [4]: data = xr.DataArray(np.random.random(size=(10, 2)),
   ...:                     dims=['samples', 'features']).chunk((5, 2))
   ...:

In [5]: compute(data.mean(axis=0))

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-5-47605102585c> in <module>()
----> 1 compute(data.mean(axis=0))

~/Envs/dask-dev/lib/python3.6/site-packages/dask/dask/base.py in compute(*args, **kwargs)
    334     results_iter = iter(results)
    335     return tuple(a if f is None else f(next(results_iter), *a)
--> 336                  for f, a in postcomputes)
    337
    338

~/Envs/dask-dev/lib/python3.6/site-packages/dask/dask/base.py in <genexpr>(.0)
    334     results_iter = iter(results)
    335     return tuple(a if f is None else f(next(results_iter), *a)
--> 336                  for f, a in postcomputes)
    337
    338

~/Envs/dask-dev/lib/python3.6/site-packages/xarray/xarray/core/dataarray.py in _dask_finalize(results, func, args, name)
    607     @staticmethod
    608     def _dask_finalize(results, func, args, name):
--> 609         ds = func(results, *args)
    610         variable = ds._variables.pop(_THIS_ARRAY)
    611         coords = ds._variables

~/Envs/dask-dev/lib/python3.6/site-packages/xarray/xarray/core/dataset.py in _dask_postcompute(results, info, *args)
    551                 func, args2 = v
    552                 r = results2.pop()
--> 553                 result = func(r, *args2)
    554             else:
    555                 result = v

~/Envs/dask-dev/lib/python3.6/site-packages/xarray/xarray/core/variable.py in _dask_finalize(results, array_func, array_args, dims, attrs, encoding)
    389             results = {k: v for k, v in results.items() if k[0] == name}  # cull
    390         data = array_func(results, *array_args)
--> 391         return Variable(dims, data, attrs=attrs, encoding=encoding)
    392
    393     @property

~/Envs/dask-dev/lib/python3.6/site-packages/xarray/xarray/core/variable.py in __init__(self, dims, data, attrs, encoding, fastpath)
    267         """
    268         self._data = as_compatible_data(data, fastpath=fastpath)
--> 269         self._dims = self._parse_dimensions(dims)
    270         self._attrs = None
    271         self._encoding = None

~/Envs/dask-dev/lib/python3.6/site-packages/xarray/xarray/core/variable.py in _parse_dimensions(self, dims)
    431             raise ValueError('dimensions %s must have the same length as the '
    432                              'number of data dimensions, ndim=%s'
--> 433                              % (dims, self.ndim))
    434         return dims
    435

ValueError: dimensions ('features',) must have the same length as the number of data dimensions, ndim=0

The expected output is the .compute version, which works correctly:

In [7]: data.mean(axis=0).compute()
Out[7]:
<xarray.DataArray (features: 2)>
array([0.535643, 0.459406])
Dimensions without coordinates: features

In [6]: xr.show_versions()

INSTALLED VERSIONS
------------------
commit: c2b205f29467a4431baa80b5c07fe31bda67fbef
python: 3.6.1.final.0
python-bits: 64
OS: Darwin
OS-release: 16.7.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

xarray: 0.10.0-5-gc2b205f
pandas: 0.22.0.dev0+118.g4c6387520
numpy: 1.14.0.dev0+2995e6a
scipy: 1.1.0.dev0+b6fd544
netCDF4: 1.3.1
h5netcdf: None
Nio: None
bottleneck: None
cyordereddict: None
dask: 0.16.0+15.gcbc62fbef
matplotlib: 2.1.0
cartopy: None
seaborn: 0.8.1
setuptools: 36.7.2
pip: 10.0.0.dev0
conda: None
pytest: 3.2.3
IPython: 6.2.1
sphinx: 1.6.5

Apologies if I’m doing something silly here, I don’t know xarray 😃