issues: 573577844

See upstream: https://github.com/zarr-developers/zarr-python/issues/551

It seems that using a ZipStore creates 1 byte objects for Unicode string attributes.

For example, saving the same Dataset with a DirectoryStore and a Zip Store creates an attribute for a unicode array with 20 bytes in size in the first, and 1 byte in size in the second.

In fact, ubuntu file roller isn't even allowing me to extract the files.

I have a feeling it is due to the note in the zarr documentation

Note that Zip files do not provide any way to remove or replace existing entries.

https://zarr.readthedocs.io/en/stable/api/storage.html#zarr.storage.ZipStore

MCVE Code Sample

ZipStore python import xarray as xr import zarr x = xr.Dataset() x['hello'] = 'world' x with zarr.ZipStore('test_store.zip', mode='w') as store: x.to_zarr(store) with zarr.ZipStore('test_store.zip', mode='r') as store: x_read = xr.open_zarr(store).compute()

Issued error

```python --------------------------------------------------------------------------- BadZipFile Traceback (most recent call last) <ipython-input-1-2a92a6db56ab> in <module> 7 x.to_zarr(store) 8 with zarr.ZipStore('test_store.zip', mode='r') as store: ----> 9 x_read = xr.open_zarr(store).compute() ~/miniconda3/envs/dev/lib/python3.7/site-packages/xarray/core/dataset.py in compute(self, **kwargs) 803 """ 804 new = self.copy(deep=False) --> 805 return new.load(**kwargs) 806 807 def _persist_inplace(self, **kwargs) -> "Dataset": ~/miniconda3/envs/dev/lib/python3.7/site-packages/xarray/core/dataset.py in load(self, **kwargs) 655 for k, v in self.variables.items(): 656 if k not in lazy_data: --> 657 v.load() 658 659 return self ~/miniconda3/envs/dev/lib/python3.7/site-packages/xarray/core/variable.py in load(self, **kwargs) 370 self._data = as_compatible_data(self._data.compute(**kwargs)) 371 elif not hasattr(self._data, "__array_function__"): --> 372 self._data = np.asarray(self._data) 373 return self 374 ~/miniconda3/envs/dev/lib/python3.7/site-packages/numpy/core/_asarray.py in asarray(a, dtype, order) 83 84 """ ---> 85 return array(a, dtype, copy=False, order=order) 86 87 ~/miniconda3/envs/dev/lib/python3.7/site-packages/xarray/core/indexing.py in __array__(self, dtype) 545 def __array__(self, dtype=None): 546 array = as_indexable(self.array) --> 547 return np.asarray(array[self.key], dtype=None) 548 549 def transpose(self, order): ~/miniconda3/envs/dev/lib/python3.7/site-packages/xarray/backends/zarr.py in __getitem__(self, key) 46 array = self.get_array() 47 if isinstance(key, indexing.BasicIndexer): ---> 48 return array[key.tuple] 49 elif isinstance(key, indexing.VectorizedIndexer): 50 return array.vindex[ ~/miniconda3/envs/dev/lib/python3.7/site-packages/zarr/core.py in __getitem__(self, selection) 570 571 fields, selection = pop_fields(selection) --> 572 return self.get_basic_selection(selection, fields=fields) 573 574 def get_basic_selection(self, selection=Ellipsis, out=None, fields=None): ~/miniconda3/envs/dev/lib/python3.7/site-packages/zarr/core.py in get_basic_selection(self, selection, out, fields) 693 if self._shape == (): 694 return self._get_basic_selection_zd(selection=selection, out=out, --> 695 fields=fields) 696 else: 697 return self._get_basic_selection_nd(selection=selection, out=out, ~/miniconda3/envs/dev/lib/python3.7/site-packages/zarr/core.py in _get_basic_selection_zd(self, selection, out, fields) 709 # obtain encoded data for chunk 710 ckey = self._chunk_key((0,)) --> 711 cdata = self.chunk_store[ckey] 712 713 except KeyError: ~/miniconda3/envs/dev/lib/python3.7/site-packages/zarr/storage.py in __getitem__(self, key) 1249 with self.mutex: 1250 with self.zf.open(key) as f: # will raise KeyError -> 1251 return f.read() 1252 1253 def __setitem__(self, key, value): ~/miniconda3/envs/dev/lib/python3.7/zipfile.py in read(self, n) 914 self._offset = 0 915 while not self._eof: --> 916 buf += self._read1(self.MAX_N) 917 return buf 918 ~/miniconda3/envs/dev/lib/python3.7/zipfile.py in _read1(self, n) 1018 if self._left <= 0: 1019 self._eof = True -> 1020 self._update_crc(data) 1021 return data 1022 ~/miniconda3/envs/dev/lib/python3.7/zipfile.py in _update_crc(self, newdata) 946 # Check the CRC if we're at the end of the file 947 if self._eof and self._running_crc != self._expected_crc: --> 948 raise BadZipFile("Bad CRC-32 for file %r" % self.name) 949 950 def read1(self, n): BadZipFile: Bad CRC-32 for file 'hello/0' 0 2 Untitled10.ipynb ```

Working Directory Store example python import xarray as xr import zarr x = xr.Dataset() x['hello'] = 'world' x store = zarr.DirectoryStore('test_store2.zarr') x.to_zarr(store) x_read = xr.open_zarr(store) x_read.compute() assert x_read.hello == x.hello

Expected Output

The string metadata should work.

Output of xr.show_versions()

``` INSTALLED VERSIONS ------------------ commit: None python: 3.7.6 | packaged by conda-forge | (default, Jan 7 2020, 22:33:48) [GCC 7.3.0] python-bits: 64 OS: Linux OS-release: 5.3.0-40-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_CA.UTF-8 LOCALE: en_CA.UTF-8 libhdf5: None libnetcdf: None xarray: 0.14.1 pandas: 1.0.0 numpy: 1.17.5 scipy: 1.4.1 netCDF4: None pydap: None h5netcdf: None h5py: None Nio: None zarr: 2.4.0 cftime: None nc_time_axis: None PseudoNetCDF: None rasterio: None cfgrib: None iris: None bottleneck: None dask: 2.10.1 distributed: 2.10.0 matplotlib: 3.1.3 cartopy: None seaborn: None numbagg: None setuptools: 45.1.0.post20200119 pip: 20.0.2 conda: None pytest: 5.3.1 IPython: 7.12.0 sphinx: 2.3.1 ```