Add warning for netCDF4 bug

Author: braaannigan

doc/whats-new.rst

@@ -68,6 +68,9 @@ Enhancements
 
 Bug fixes
 ~~~~~~~~~
+- Added warning in api.py of a netCDF4 bug that occurs when
+  the filepath has 88 characters (:issue:`1745`).
+  By `Liam Brannigan <https://github.com/braaannigan>` _.
 - Fixed encoding of multi-dimensional coordinates in
   :py:meth:`~Dataset.to_netcdf` (:issue:`1763`).
   By `Mike Neish <https://github.com/neishm>`_.

xarray/backends/netCDF4_.py

@@ -3,6 +3,8 @@
 from __future__ import print_function
 import functools
 import operator
+import warnings
+from distutils.version import LooseVersion
 
 import numpy as np
 
@@ -244,6 +246,17 @@ def __init__(self, netcdf4_dataset, mode='r', writer=None, opener=None,
     def open(cls, filename, mode='r', format='NETCDF4', group=None,
              writer=None, clobber=True, diskless=False, persist=False,
              autoclose=False):
+        import netCDF4 as nc4
+        if (len(filename) == 88 and
+                LooseVersion(nc4.__version__) < "1.3.1"):
+            warnings.warn(
+                '\nA segmentation fault may occur when the\n'
+                'file path has exactly 88 characters as it does.\n'
+                'in this case. The issue is known to occur with\n'
+                'version 1.2.4 of netCDF4 and can be addressed by\n'
+                'upgrading netCDF4 to at least version 1.3.1.\n'
+                'More details can be found here:\n'
+                'https://github.com/pydata/xarray/issues/1745  \n')
         if format is None:
             format = 'NETCDF4'
         opener = functools.partial(_open_netcdf4_group, filename, mode=mode,

xarray/tests/test_backends.py

@@ -10,6 +10,7 @@
 import tempfile
 import unittest
 import sys
+import warnings
 
 import numpy as np
 import pandas as pd
@@ -1056,6 +1057,15 @@ def test_unsorted_index_raises(self):
             except IndexError as err:
                 self.assertIn('first by calling .load', str(err))
 
+    def test_88_character_filename_segmentation_fault(self):
+        # should be fixed in netcdf4 v1.3.1
+        with mock.patch('netCDF4.__version__', '1.2.4'):
+            with warnings.catch_warnings():
+                warnings.simplefilter("error")
+                with raises_regex(Warning, 'segmentation fault'):
+                    # Need to construct 88 character filepath
+                    xr.Dataset().to_netcdf('a' * (88 - len(os.getcwd()) - 1))
+
 
 class NetCDF4DataStoreAutocloseTrue(NetCDF4DataTest):
     autoclose = True