xarray.load_dataarray fails when loading a DataArray with coordinates via zarr-fsspec

[csubich]

What happened?

When loading a zarr-backed DataArray via a fsspec URL, if the DataArray has coordinates xarray appears to treat the load as a request for a Dataset, not a DataArray. It then seeks to load the coordinate as a distinct variable within the file, where it is not present.

This issue does not occur when loading a DirectoryStore-backed zarr; the coordinate dimension is loaded successfully.

What did you expect to happen?

Behaviour should be identical between DirectoryStore backed DataArrays and FSSpec-backed DirectoryArrays, and both should support arrays with coordinates.

Minimal Complete Verifiable Example

# /// script
# requires-python = ">=3.11"
# dependencies = [
#   "xarray[complete]@git+https://github.com/pydata/xarray.git@main",
# ]
# ///
#
# This script automatically imports the development branch of xarray to check for issues.
# Please delete this header if you have _not_ tested this script with `uv run`!

import xarray as xr
xr.show_versions()
# your reproducer code ...

import xarray as xr
import numpy as np
import os
os.system('rm -rf good.zipstore.zip')
os.system('rm -rf bad.zipstore.zip')
os.system('rm -rf good.dirstore.zarr')
os.system('rm -rf bad.dirstore.zarr')

## Working example, no coordinates
foo = xr.DataArray(data=np.zeros(1),
             dims='foo')
             # coords={'foo' : [0]})

foo.to_zarr('good.dirstore.zarr',consolidated=False,zarr_format=3).close()
# Make zipstore
os.system('cd good.dirstore.zarr; zip -0rv ../good.zipstore.zip ./')

foo_dirstore = xr.load_dataarray('good.dirstore.zarr',engine='zarr',zarr_format=3,consolidated=False)
print(foo_dirstore)
# <xarray.DataArray (foo: 1)> Size: 8B
# array([0.])
# Dimensions without coordinates: foo

foo_zipstore = xr.load_dataarray('zip:///::good.zipstore.zip',engine='zarr',zarr_format=3,consolidated=False)
print(foo_zipstore)
# <xarray.DataArray (foo: 1)> Size: 8B
# array([0.])
# Dimensions without coordinates: foo

## Broken example, with coordinates
foo = xr.DataArray(data=np.zeros(1),
             dims='foo',
             coords={'foo' : [0]})

foo.to_zarr('bad.dirstore.zarr',consolidated=False,zarr_format=3).close()

# Make zipstore
os.system('cd bad.dirstore.zarr; zip -0rv ../bad.zipstore.zip ./')

foo_dirstore = xr.load_dataarray('bad.dirstore.zarr',engine='zarr',zarr_format=3,consolidated=False)
print(foo_dirstore)
# <xarray.DataArray (foo: 1)> Size: 8B
# array([0.])
# Coordinates:
#   * foo      (foo) int64 8B 0

foo_zipstore = xr.load_dataarray('zip:///::bad.zipstore.zip',engine='zarr',zarr_format=3,consolidated=False)
print(foo_zipstore)
# KeyError                                  Traceback (most recent call last)
# /tmp/ipython-input-2393741926.py in <cell line: 0>()
# ----> 1 foo_zipstore = xr.load_dataarray('zip:///::bad.zipstore.zip',engine='zarr',zarr_format=3,consolidated=False)
#       2 print(foo_zipstore)

# ...
# /usr/lib/python3.12/zipfile/__init__.py in getinfo(self, name)
#    1547         info = self.NameToInfo.get(name)
#    1548         if info is None:
# -> 1549             raise KeyError(
#    1550                 'There is no item named %r in the archive' % name)
#    1551 

# KeyError: "There is no item named 'foo/c/0' in the archive"

Steps to reproduce

See MCVE: write a DataArray containing coordinates to a DirectoryStore, zip it to a ZipStore, and open the file via a fsspec zip:// URL. MCVE tested on google colab.

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

<xarray.DataArray (foo: 1)> Size: 8B
array([0.])
Dimensions without coordinates: foo
<xarray.DataArray (foo: 1)> Size: 8B
array([0.])
Dimensions without coordinates: foo
<xarray.DataArray (foo: 1)> Size: 8B
array([0.])
Coordinates:
  * foo      (foo) int64 8B 0
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
/tmp/ipython-input-3205390801.py in <cell line: 0>()
     45 #   * foo      (foo) int64 8B 0
     46 
---> 47 foo_zipstore = xr.load_dataarray('zip:///::bad.zipstore.zip',engine='zarr',zarr_format=3,consolidated=False)
     48 print(foo_zipstore)
     49 # KeyError                                  Traceback (most recent call last)

35 frames
/usr/local/lib/python3.12/dist-packages/xarray/backends/api.py in load_dataarray(filename_or_obj, **kwargs)
    189         raise TypeError("cache has no effect in this context")
    190 
--> 191     with open_dataarray(filename_or_obj, **kwargs) as da:
    192         return da.load()
    193 

/usr/local/lib/python3.12/dist-packages/xarray/backends/api.py in open_dataarray(filename_or_obj, engine, chunks, cache, decode_cf, mask_and_scale, decode_times, decode_timedelta, use_cftime, concat_characters, decode_coords, drop_variables, create_default_indexes, inline_array, chunked_array_type, from_array_kwargs, backend_kwargs, **kwargs)
    811     """
    812 
--> 813     dataset = open_dataset(
    814         filename_or_obj,
    815         decode_cf=decode_cf,

/usr/local/lib/python3.12/dist-packages/xarray/backends/api.py in open_dataset(filename_or_obj, engine, chunks, cache, decode_cf, mask_and_scale, decode_times, decode_timedelta, use_cftime, concat_characters, decode_coords, drop_variables, create_default_indexes, inline_array, chunked_array_type, from_array_kwargs, backend_kwargs, **kwargs)
    610         **kwargs,
    611     )
--> 612     ds = _dataset_from_backend_dataset(
    613         backend_ds,
    614         filename_or_obj,

/usr/local/lib/python3.12/dist-packages/xarray/backends/api.py in _dataset_from_backend_dataset(backend_ds, filename_or_obj, engine, chunks, cache, overwrite_encoded_chunks, inline_array, chunked_array_type, from_array_kwargs, create_default_indexes, **extra_tokens)
    300 
    301     if create_default_indexes:
--> 302         ds = _maybe_create_default_indexes(backend_ds)
    303     else:
    304         ds = backend_ds

/usr/local/lib/python3.12/dist-packages/xarray/backends/api.py in _maybe_create_default_indexes(ds)
    276         if coord.dims == (name,) and name not in ds.xindexes
    277     }
--> 278     return ds.assign_coords(Coordinates(to_index))
    279 
    280 

/usr/local/lib/python3.12/dist-packages/xarray/core/coordinates.py in __init__(self, coords, indexes)
    313                 var = as_variable(data, name=name, auto_convert=False)
    314                 if var.dims == (name,) and indexes is None:
--> 315                     index, index_vars = create_default_index_implicit(var, list(coords))
    316                     default_indexes.update(dict.fromkeys(index_vars, index))
    317                     variables.update(index_vars)

/usr/local/lib/python3.12/dist-packages/xarray/core/indexes.py in create_default_index_implicit(dim_variable, all_variables)
   1636     else:
   1637         dim_var = {name: dim_variable}
-> 1638         index = PandasIndex.from_variables(dim_var, options={})
   1639         index_vars = index.create_variables(dim_var)
   1640 

/usr/local/lib/python3.12/dist-packages/xarray/core/indexes.py in from_variables(cls, variables, options)
    718         # preserve wrapped pd.Index (if any)
    719         # accessing `.data` can load data from disk, so we only access if needed
--> 720         data = var._data if isinstance(var._data, PandasIndexingAdapter) else var.data  # type: ignore[redundant-expr]
    721         # multi-index level variable: get level index
    722         if isinstance(var._data, PandasMultiIndexingAdapter):

/usr/local/lib/python3.12/dist-packages/xarray/core/variable.py in data(self)
    454             duck_array = self._data.array
    455         elif isinstance(self._data, indexing.ExplicitlyIndexed):
--> 456             duck_array = self._data.get_duck_array()
    457         elif is_duck_array(self._data):
    458             duck_array = self._data

/usr/local/lib/python3.12/dist-packages/xarray/core/indexing.py in get_duck_array(self)
    941 
    942     def get_duck_array(self):
--> 943         duck_array = self.array.get_duck_array()
    944         # ensure the array object is cached in-memory
    945         self.array = as_indexable(duck_array)

/usr/local/lib/python3.12/dist-packages/xarray/core/indexing.py in get_duck_array(self)
    895 
    896     def get_duck_array(self):
--> 897         return self.array.get_duck_array()
    898 
    899     async def async_get_duck_array(self):

/usr/local/lib/python3.12/dist-packages/xarray/core/indexing.py in get_duck_array(self)
    735 
    736         if isinstance(self.array, BackendArray):
--> 737             array = self.array[self.key]
    738         else:
    739             array = apply_indexer(self.array, self.key)

/usr/local/lib/python3.12/dist-packages/xarray/backends/zarr.py in __getitem__(self, key)
    260         elif isinstance(key, indexing.OuterIndexer):
    261             method = self._oindex
--> 262         return indexing.explicit_indexing_adapter(
    263             key, array.shape, indexing.IndexingSupport.VECTORIZED, method
    264         )

/usr/local/lib/python3.12/dist-packages/xarray/core/indexing.py in explicit_indexing_adapter(key, shape, indexing_support, raw_indexing_method)
   1127     """
   1128     raw_key, numpy_indices = decompose_indexer(key, shape, indexing_support)
-> 1129     result = raw_indexing_method(raw_key.tuple)
   1130     if numpy_indices.tuple:
   1131         # index the loaded duck array

/usr/local/lib/python3.12/dist-packages/xarray/backends/zarr.py in _getitem(self, key)
    223 
    224     def _getitem(self, key):
--> 225         return self._array[key]
    226 
    227     async def _async_getitem(self, key):

/usr/local/lib/python3.12/dist-packages/zarr/core/array.py in __getitem__(self, selection)
   2866             return self.vindex[cast("CoordinateSelection | MaskSelection", selection)]
   2867         elif is_pure_orthogonal_indexing(pure_selection, self.ndim):
-> 2868             return self.get_orthogonal_selection(pure_selection, fields=fields)
   2869         else:
   2870             return self.get_basic_selection(cast("BasicSelection", pure_selection), fields=fields)

/usr/local/lib/python3.12/dist-packages/zarr/core/array.py in get_orthogonal_selection(self, selection, out, fields, prototype)
   3337             prototype = default_buffer_prototype()
   3338         indexer = OrthogonalIndexer(selection, self.shape, self.metadata.chunk_grid)
-> 3339         return sync(
   3340             self.async_array._get_selection(
   3341                 indexer=indexer, out=out, fields=fields, prototype=prototype

/usr/local/lib/python3.12/dist-packages/zarr/core/sync.py in sync(coro, loop, timeout)
    157 
    158     if isinstance(return_result, BaseException):
--> 159         raise return_result
    160     else:
    161         return return_result

/usr/local/lib/python3.12/dist-packages/zarr/core/sync.py in _runner(coro)
    117     """
    118     try:
--> 119         return await coro
    120     except Exception as ex:
    121         return ex

/usr/local/lib/python3.12/dist-packages/zarr/core/array.py in _get_selection(self, indexer, prototype, out, fields)
   1563 
   1564             # reading chunks and decoding them
-> 1565             await self.codec_pipeline.read(
   1566                 [
   1567                     (

/usr/local/lib/python3.12/dist-packages/zarr/core/codec_pipeline.py in read(self, batch_info, out, drop_axes)
    471         drop_axes: tuple[int, ...] = (),
    472     ) -> None:
--> 473         await concurrent_map(
    474             [
    475                 (single_batch_info, out, drop_axes)

/usr/local/lib/python3.12/dist-packages/zarr/core/common.py in concurrent_map(items, func, limit)
    114                 return await func(*item)
    115 
--> 116         return await asyncio.gather(*[asyncio.ensure_future(run(item)) for item in items])
    117 
    118 

/usr/local/lib/python3.12/dist-packages/zarr/core/common.py in run(item)
    112         async def run(item: tuple[Any]) -> V:
    113             async with sem:
--> 114                 return await func(*item)
    115 
    116         return await asyncio.gather(*[asyncio.ensure_future(run(item)) for item in items])

/usr/local/lib/python3.12/dist-packages/zarr/core/codec_pipeline.py in read_batch(self, batch_info, out, drop_axes)
    268                     out[out_selection] = fill_value_or_default(chunk_spec)
    269         else:
--> 270             chunk_bytes_batch = await concurrent_map(
    271                 [(byte_getter, array_spec.prototype) for byte_getter, array_spec, *_ in batch_info],
    272                 lambda byte_getter, prototype: byte_getter.get(prototype),

/usr/local/lib/python3.12/dist-packages/zarr/core/common.py in concurrent_map(items, func, limit)
    114                 return await func(*item)
    115 
--> 116         return await asyncio.gather(*[asyncio.ensure_future(run(item)) for item in items])
    117 
    118 

/usr/local/lib/python3.12/dist-packages/zarr/core/common.py in run(item)
    112         async def run(item: tuple[Any]) -> V:
    113             async with sem:
--> 114                 return await func(*item)
    115 
    116         return await asyncio.gather(*[asyncio.ensure_future(run(item)) for item in items])

/usr/local/lib/python3.12/dist-packages/zarr/storage/_common.py in get(self, prototype, byte_range)
    166         if prototype is None:
    167             prototype = default_buffer_prototype()
--> 168         return await self.store.get(self.path, prototype=prototype, byte_range=byte_range)
    169 
    170     async def set(self, value: Buffer) -> None:

/usr/local/lib/python3.12/dist-packages/zarr/storage/_fsspec.py in get(self, key, prototype, byte_range)
    287         try:
    288             if byte_range is None:
--> 289                 value = prototype.buffer.from_bytes(await self.fs._cat_file(path))
    290             elif isinstance(byte_range, RangeByteRequest):
    291                 value = prototype.buffer.from_bytes(

/usr/local/lib/python3.12/dist-packages/fsspec/implementations/asyn_wrapper.py in wrapper(*args, **kwargs)
     25     @functools.wraps(func)
     26     async def wrapper(*args, **kwargs):
---> 27         return await asyncio.to_thread(func, *args, **kwargs)
     28 
     29     return wrapper

/usr/lib/python3.12/asyncio/threads.py in to_thread(func, *args, **kwargs)
     23     ctx = contextvars.copy_context()
     24     func_call = functools.partial(ctx.run, func, *args, **kwargs)
---> 25     return await loop.run_in_executor(None, func_call)

/usr/lib/python3.12/concurrent/futures/thread.py in run(self)
     57 
     58         try:
---> 59             result = self.fn(*self.args, **self.kwargs)
     60         except BaseException as exc:
     61             self.future.set_exception(exc)

/usr/local/lib/python3.12/dist-packages/fsspec/spec.py in cat_file(self, path, start, end, **kwargs)
    767         """
    768         # explicitly set buffering off?
--> 769         with self.open(path, "rb", **kwargs) as f:
    770             if start is not None:
    771                 if start >= 0:

/usr/local/lib/python3.12/dist-packages/fsspec/spec.py in open(self, path, mode, block_size, cache_options, compression, **kwargs)
   1308         else:
   1309             ac = kwargs.pop("autocommit", not self._intrans)
-> 1310             f = self._open(
   1311                 path,
   1312                 mode=mode,

/usr/local/lib/python3.12/dist-packages/fsspec/implementations/zip.py in _open(self, path, mode, block_size, autocommit, cache_options, **kwargs)
    128         if "r" in self.mode and "w" in mode:
    129             raise OSError("ZipFS can only be open for reading or writing, not both")
--> 130         out = self.zip.open(path, mode.strip("b"), force_zip64=self.force_zip_64)
    131         if "r" in mode:
    132             info = self.info(path)

/usr/lib/python3.12/zipfile/__init__.py in open(self, name, mode, pwd, force_zip64)
   1619         else:
   1620             # Get info object for name
-> 1621             zinfo = self.getinfo(name)
   1622 
   1623         if mode == 'w':

/usr/lib/python3.12/zipfile/__init__.py in getinfo(self, name)
   1547         info = self.NameToInfo.get(name)
   1548         if info is None:
-> 1549             raise KeyError(
   1550                 'There is no item named %r in the archive' % name)
   1551 

KeyError: "There is no item named 'foo/c/0' in the archive"

Anything else we need to know?

No response

Environment

INSTALLED VERSIONS

commit: None
python: 3.12.12 (main, Oct 10 2025, 08:52:57) [GCC 11.4.0]
python-bits: 64
OS: Linux
OS-release: 6.6.105+
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: en_US.UTF-8
LANG: en_US.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.14.6
libnetcdf: 4.9.3

xarray: 2025.11.1.dev8+g6e82a3afa
pandas: 2.2.2
numpy: 2.0.2
scipy: 1.16.3
netCDF4: 1.7.3
pydap: 3.5.8
h5netcdf: 1.7.3
h5py: 3.15.1
zarr: 3.1.5
cftime: 1.6.5
nc_time_axis: 1.4.1
iris: None
bottleneck: 1.4.2
dask: 2025.9.1
distributed: 2025.9.1
matplotlib: 3.10.0
cartopy: 0.25.0
seaborn: 0.13.2
numbagg: 0.9.3
fsspec: 2025.3.0
cupy: 13.6.0
pint: None
sparse: 0.17.0
flox: 0.10.7
numpy_groupies: 0.11.3
setuptools: 75.2.0
pip: 24.1.2
conda: None
pytest: 8.4.2
mypy: None
IPython: 7.34.0
sphinx: 8.2.3

[shoyer]

Looking at your example, my guess is that this may be something specific to Zip-based Zarr stores? I wonder if the issue is simply that loading from Zip-based Zarr stores with multiple variables don't work. (Note that the DataArray.to_zarr() is implemented by first converting the DataArray into a Dataset.)

[csubich]

It seems specific to fsspec-backed zarr stores. Passing aZipStore object directly to open_dataarray succeeds, but a FsspecStore object fails:

import zarr
## ZipStore works
specstore = zarr.storage.ZipStore('bad.zipstore.zip',mode='r')
specstore._sync_open() # Work around zarr bug
foo_zarrstore = xr.load_dataarray(specstore,engine='zarr',zarr_format=3,consolidated=False)
print(foo_zarrstore)
# <xarray.DataArray (foo: 1)> Size: 8B
# array([0.])
# Coordinates:
#   * foo      (foo) int64 8B 0

## FsspecStore fails
import fsspec
from fsspec.implementations.asyn_wrapper import AsyncFileSystemWrapper
fsspec_store = zarr.storage.FsspecStore(AsyncFileSystemWrapper(fsspec.core.url_to_fs('zip:///::bad.zipstore.zip')[0]))

foo_fsspecstore = xr.load_dataarray(fsspec_store,engine='zarr',zarr_format=3,consolidated=False)
# KeyError                                  Traceback (most recent call last)
# [/tmp/ipython-input-4212981506.py](https://localhost:8080/#) in <cell line: 0>()
#       2 fsspec_store = zarr.storage.FsspecStore(AsyncFileSystemWrapper(fsspec.core.url_to_fs('zip:///::bad.zipstore.zip')[0]))
#       3 
# ----> 4 foo_fsspecstore = xr.load_dataarray(fsspec_store,engine='zarr',zarr_format=3,consolidated=False)
#      5 print(foo_fsspecstore)
# [...]
# [/usr/lib/python3.12/zipfile/__init__.py](https://localhost:8080/#) in getinfo(self, name)
#    1547         info = self.NameToInfo.get(name)
#    1548         if info is None:
# -> 1549             raise KeyError(
#    1550                 'There is no item named %r in the archive' % name)
#    1551 
# 
# KeyError: "There is no item named 'foo/c/0' in the archive"

Unfortunately, it's not easy to work around fsspec. Modern versions of xarray (and/or zarr) have dropped some of the automatic handling of zarr file types by extension, so the most natural way to have a program work seamlessly with either directory-backed zarrs or zip-backed zarrs is to use the url construction.

[shoyer]

Do you see it for other non-zip stores wrapped in fsspec?

…

On Wed, Nov 26, 2025 at 7:10 PM csubich ***@***.***> wrote: *csubich* left a comment (pydata/xarray#10950) <#10950 (comment)> It seems specific to fsspec-backed zarr stores. Passing aZipStore object directly to open_dataarray succeeds, but a FsspecStore object fails: import zarr## ZipStore worksspecstore = zarr.storage.ZipStore('bad.zipstore.zip',mode='r')specstore._sync_open() # Work around zarr bugfoo_zarrstore = xr.load_dataarray(specstore,engine='zarr',zarr_format=3,consolidated=False)print(foo_zarrstore)# <xarray.DataArray (foo: 1)> Size: 8B# array([0.])# Coordinates:# * foo (foo) int64 8B 0 ## FsspecStore failsimport fsspecfrom fsspec.implementations.asyn_wrapper import AsyncFileSystemWrapperfsspec_store = zarr.storage.FsspecStore(AsyncFileSystemWrapper(fsspec.core.url_to_fs('zip:///::bad.zipstore.zip')[0])) foo_fsspecstore = xr.load_dataarray(fsspec_store,engine='zarr',zarr_format=3,consolidated=False)# KeyError Traceback (most recent call last)# [/tmp/ipython-input-4212981506.py](https://localhost:8080/#) in <cell line: 0>()# 2 fsspec_store = zarr.storage.FsspecStore(AsyncFileSystemWrapper(fsspec.core.url_to_fs('zip:///::bad.zipstore.zip')[0]))# 3 # ----> 4 foo_fsspecstore = xr.load_dataarray(fsspec_store,engine='zarr',zarr_format=3,consolidated=False)# 5 print(foo_fsspecstore) Unfortunately, it's not easy to work around fsspec. Modern versions of xarray (and/or zarr) have dropped some of the automatic handling of zarr file types by extension, so the most natural way to have a program work seamlessly with either directory-backed zarrs or zip-backed zarrs is to use the url construction. — Reply to this email directly, view it on GitHub <#10950 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAJJFVXXNIOPJRS66QA6GFT36ZTSPAVCNFSM6AAAAACNI47DCWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTKOBUGAZTIMRYGY> . You are receiving this because you commented.Message ID: ***@***.***>

[csubich]

A quick test suggests that a DirFileSystem-backed store works:

from fsspec.implementations.dirfs import DirFileSystem
bad_dir_fsspec = AsyncFileSystemWrapper(DirFileSystem('bad.dirstore.zarr'))
bad_fs_storage = zarr.storage.FsspecStore(bad_dir_fsspec)
print(xr.load_dataarray(bad_fs_storage,engine='zarr',zarr_format=3,consolidated=False))

# <xarray.DataArray (foo: 1)> Size: 8B
# array([0.])
# Coordinates:
#   * foo      (foo) int64 8B 0

I can't directly pass a dir:: fsspec-url to open_dataarray because xarray doesn't perform the requisite AsyncFileSystemWrapper for that protocol (which makes me wonder how the zip one works?).

Frankly I'm a bit flummoxed; I would have expected all fsspec-stores to be essentially indistinguishable at the level of xarray.

[csubich]

One difference appears to be that ZipStore and FsspecStore views of the file don't present the same set of keys:

zipstore = zarr.storage.ZipStore('bad.zipstore.zip',mode='r')
zipstore._sync_open() # Work around zarr bug
async for k in zipstore.list():
  print(k)

# __xarray_dataarray_variable__/
# __xarray_dataarray_variable__/c/
# __xarray_dataarray_variable__/c/0
# __xarray_dataarray_variable__/zarr.json
# foo/
# foo/zarr.json
# zarr.json

fsspec_store = zarr.storage.FsspecStore(AsyncFileSystemWrapper(fsspec.core.url_to_fs('zip:///::bad.zipstore.zip')[0]))
async for k in fsspec_store.list():
  print(k)

# __xarray_dataarray_variable__/c/0
# __xarray_dataarray_variable__/zarr.json
# foo/zarr.json
# zarr.json

I'm not sure how that's translating to the above error, however, since the KeyError foo/c/0 is in neither view.