issues: 681864788

What happened:

A file that isn't obviously malformed or corrupted that I try to load using opendap generates an esoteric IndexError from dask.

What you expected to happen:

For the file to load successfully.

Minimal Complete Verifiable Example:

python url = "http://iridl.ldeo.columbia.edu/SOURCES/.Models/.NMME/.NCEP-CFSv2/.HINDCAST/.MONTHLY/.tref/dods" ds_test = xr.open_dataset(url, decode_times=False) print(ds_test) ds_test.load()

This yields the following:

```python <xarray.Dataset> Dimensions: (L: 10, M: 24, S: 348, X: 360, Y: 181) Coordinates: * M (M) float32 1.0 2.0 3.0 4.0 5.0 6.0 ... 20.0 21.0 22.0 23.0 24.0 * X (X) float32 0.0 1.0 2.0 3.0 4.0 ... 355.0 356.0 357.0 358.0 359.0 * L (L) float32 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5 * S (S) float32 264.0 265.0 266.0 267.0 ... 608.0 609.0 610.0 611.0 * Y (Y) float32 -90.0 -89.0 -88.0 -87.0 -86.0 ... 87.0 88.0 89.0 90.0 Data variables: tref (S, L, M, Y, X) float32 ... Attributes: Conventions: IRIDL

---

IndexError Traceback (most recent call last) ~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/backends/netCDF4_.py in _getitem(self, key) 84 original_array = self.get_array(needs_lock=False) ---> 85 array = getitem(original_array, key) 86 except IndexError:

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/backends/common.py in robust_getitem(array, key, catch, max_retries, initial_delay) 53 try: ---> 54 return array[key] 55 except catch:

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Variable.getitem()

netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Variable._get()

IndexError: index exceeds dimension bounds

During handling of the above exception, another exception occurred:

IndexError Traceback (most recent call last) <ipython-input-9-23bd037d898e> in <module> 2 ds_test = xr.open_dataset(url, decode_times=False) 3 print(ds_test) ----> 4 ds_test.load()

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/core/dataset.py in load(self, **kwargs) 664 for k, v in self.variables.items(): 665 if k not in lazy_data: --> 666 v.load() 667 668 return self

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/core/variable.py in load(self, kwargs) 379 self._data = as_compatible_data(self._data.compute(kwargs)) 380 elif not hasattr(self._data, "array_function"): --> 381 self._data = np.asarray(self._data) 382 return self 383

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/numpy/core/_asarray.py in asarray(a, dtype, order) 81 82 """ ---> 83 return array(a, dtype, copy=False, order=order) 84 85

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/core/indexing.py in array(self, dtype) 675 676 def array(self, dtype=None): --> 677 self._ensure_cached() 678 return np.asarray(self.array, dtype=dtype) 679

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/core/indexing.py in _ensure_cached(self) 672 def _ensure_cached(self): 673 if not isinstance(self.array, NumpyIndexingAdapter): --> 674 self.array = NumpyIndexingAdapter(np.asarray(self.array)) 675 676 def array(self, dtype=None):

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/numpy/core/_asarray.py in asarray(a, dtype, order) 81 82 """ ---> 83 return array(a, dtype, copy=False, order=order) 84 85

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/core/indexing.py in array(self, dtype) 651 652 def array(self, dtype=None): --> 653 return np.asarray(self.array, dtype=dtype) 654 655 def getitem(self, key):

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/numpy/core/_asarray.py in asarray(a, dtype, order) 81 82 """ ---> 83 return array(a, dtype, copy=False, order=order) 84 85

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/core/indexing.py in array(self, dtype) 555 def array(self, dtype=None): 556 array = as_indexable(self.array) --> 557 return np.asarray(array[self.key], dtype=None) 558 559 def transpose(self, order):

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/backends/netCDF4_.py in getitem(self, key) 71 def getitem(self, key): 72 return indexing.explicit_indexing_adapter( ---> 73 key, self.shape, indexing.IndexingSupport.OUTER, self._getitem 74 ) 75

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/core/indexing.py in explicit_indexing_adapter(key, shape, indexing_support, raw_indexing_method) 835 """ 836 raw_key, numpy_indices = decompose_indexer(key, shape, indexing_support) --> 837 result = raw_indexing_method(raw_key.tuple) 838 if numpy_indices.tuple: 839 # index the loaded np.ndarray

~/miniconda3/envs/ensinoo/lib/python3.7/site-packages/xarray/backends/netCDF4_.py in _getitem(self, key) 93 "your data into memory first by calling .load()." 94 ) ---> 95 raise IndexError(msg) 96 return array 97

IndexError: The indexing operation you are attempting to perform is not valid on netCDF4.Variable object. Try loading your data into memory first by calling .load(). ```

Anything else we need to know?:

There's something specific to this file for sure that's causing this, as I'm able to load (for expediency, a subset of) the file from the xarray docs section on opendap successfully:

```python url = "http://iridl.ldeo.columbia.edu/SOURCES/.OSU/.PRISM/.monthly/.tdmean/[X+]average/dods" ds_test = xr.open_dataset(url, decode_times=False) print(ds_test)

<xarray.Dataset> Dimensions: (T: 1420, Y: 621) Coordinates: * Y (Y) float32 49.916668 49.875 49.833336 ... 24.125 24.083334 * T (T) float32 -779.5 -778.5 -777.5 -776.5 ... 636.5 637.5 638.5 639.5 Data variables: tdmean (T, Y) float64 ... Attributes: Conventions: IRIDL ```

And then calling ds_test.load() works just fine.

Environment:

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

INSTALLED VERSIONS ------------------ commit: None python: 3.7.3 | packaged by conda-forge | (default, Jul 1 2019, 21:52:21) [GCC 7.3.0] python-bits: 64 OS: Linux OS-release: 3.10.0-862.14.4.el7.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8 libhdf5: 1.10.6 libnetcdf: 4.7.4 xarray: 0.16.0 pandas: 1.1.0 numpy: 1.19.1 scipy: 1.5.2 netCDF4: 1.5.4 pydap: installed h5netcdf: 0.8.1 h5py: 2.10.0 Nio: None zarr: 2.4.0 cftime: 1.2.1 nc_time_axis: 1.2.0 PseudoNetCDF: None rasterio: None cfgrib: 0.9.8.2 iris: None bottleneck: None dask: 2.20.0 distributed: 2.20.0 matplotlib: 3.2.1 cartopy: 0.18.0 seaborn: 0.10.1 numbagg: None pint: None setuptools: 49.6.0.post20200814 pip: 20.2.2 conda: None pytest: None IPython: 7.8.0 sphinx: None None