I was saving my dataset into a ZipStore -- apparently succesfully -- but then I couldn't reopen them.

The issue appears to be that a regular DirectoryStore behaves a little differently: it doesn't need to be closed, while a ZipStore.

(I'm not sure how this relates to #2586, the remarks there don't appear to be applicable anymore.)

MCVE Code Sample

This errors: ```python import xarray as xr import zarr

works as expected

ds = xr.Dataset({'foo': [2,3,4], 'bar': ('x', [1, 2]), 'baz': 3.14}) ds.to_zarr(zarr.DirectoryStore("test.zarr")) print(xr.open_zarr(zarr.DirectoryStore("test.zarr")))

error with ValueError "group not found at path ''

ds.to_zarr(zarr.ZipStore("test.zip")) print(xr.open_zarr(zarr.ZipStore("test.zip"))) ```

Calling close, or using with does the trick:

```python store = zarr.ZipStore("test2.zip") ds.to_zarr(store) store.close() print(xr.open_zarr(zarr.ZipStore("test2.zip")))

with zarr.ZipStore("test3.zip") as store: ds.to_zarr(store) print(xr.open_zarr(zarr.ZipStore("test3.zip"))) ```

Expected Output

I think it would be preferable to close the ZipStore in this case. But I might be missing something?

Problem Description

Because to_zarr works in this situation with a DirectoryStore, it's easy to assume a ZipStore will work similarly. However, I couldn't get it to read my data back in this case.

Versions

Output of <tt>xr.show_versions()</tt>

INSTALLED VERSIONS ------------------ commit: None python: 3.7.6 | packaged by conda-forge | (default, Jan 7 2020, 21:48:41) [MSC v.1916 64 bit (AMD64)] python-bits: 64 OS: Windows OS-release: 10 machine: AMD64 processor: Intel64 Family 6 Model 158 Stepping 9, GenuineIntel byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: None.None libhdf5: 1.10.5 libnetcdf: 4.7.3 xarray: 0.15.2.dev41+g8415eefa.d20200419 pandas: 0.25.3 numpy: 1.17.5 scipy: 1.3.1 netCDF4: 1.5.3 pydap: None h5netcdf: None h5py: 2.10.0 Nio: None zarr: 2.4.0 cftime: 1.0.4.2 nc_time_axis: None PseudoNetCDF: None rasterio: 1.1.2 cfgrib: None iris: None bottleneck: 1.3.2 dask: 2.14.0+23.gbea4c9a2 distributed: 2.14.0 matplotlib: 3.1.2 cartopy: None seaborn: 0.10.0 numbagg: None pint: None setuptools: 46.1.3.post20200325 pip: 20.0.2 conda: None pytest: 5.3.4 IPython: 7.13.0