issues: 894497993

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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
894497993 MDU6SXNzdWU4OTQ0OTc5OTM= 5331 AttributeError using map_blocks with dask 2021.05.0 9010180 closed 0     3 2021-05-18T15:18:53Z 2021-05-19T08:01:07Z 2021-05-19T08:01:07Z NONE      

What happened:

In an environment with xarray 0.18.0 and dask 2021.05.0 installed, I saved a dataset using to_zarr, opened it again using open_zarr, and called map_blocks on one of its variables. I got the following traceback:

Traceback (most recent call last): File "/home/pont/./dasktest2.py", line 12, in <module> ds2.myvar.map_blocks(lambda block: block) File "/home/pont/loc/envs/xcube-repos/lib/python3.9/site-packages/xarray/core/dataarray.py", line 3770, in map_blocks return map_blocks(func, self, args, kwargs, template) File "/home/pont/loc/envs/xcube-repos/lib/python3.9/site-packages/xarray/core/parallel.py", line 565, in map_blocks data = dask.array.Array( File "/home/pont/loc/envs/xcube-repos/lib/python3.9/site-packages/dask/array/core.py", line 1159, in __new__ if layer.collection_annotations is None: AttributeError: 'dict' object has no attribute 'collection_annotations'

What you expected to happen:

I expected map_blocks to complete successfully.

Minimal Complete Verifiable Example:

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

ds1 = xr.Dataset({ "myvar": (("x"), np.zeros(10)), "x": ("x", np.arange(10)), })
ds1.to_zarr("test.zarr", mode="w") ds2 = xr.open_zarr("test.zarr") ds2.myvar.map_blocks(lambda block: block) ```

Anything else we need to know?:

I wasn't sure whether to report this issue with dask or xcube. With dask 2021.04.1 the example runs without error, and it seems that dask PR 7309 introduced the breaking change. But my understanding of xarray's map_blocks implementation isn't sufficient to figure out where exactly the bug lies.

Environment:

Output of <tt>xr.show_versions()</tt> INSTALLED VERSIONS ------------------ commit: None python: 3.9.4 | packaged by conda-forge | (default, May 10 2021, 22:13:33) [GCC 9.3.0] python-bits: 64 OS: Linux OS-release: 5.8.0-53-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_GB.UTF-8 LOCALE: en_GB.UTF-8 libhdf5: None libnetcdf: None xarray: 0.18.0 pandas: 1.2.4 numpy: 1.20.2 scipy: None netCDF4: None pydap: None h5netcdf: None h5py: None Nio: None zarr: 2.8.1 cftime: None nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: None dask: 2021.05.0 distributed: 2021.05.0 matplotlib: None cartopy: None seaborn: None numbagg: None pint: None setuptools: 49.6.0.post20210108 pip: 21.1.1 conda: None pytest: None IPython: None sphinx: None 
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   completed 13221727 issue

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