BUG: Pass kwargs to the FileManager for pynio engine (#2380)

doc/whats-new.rst

@@ -79,6 +79,9 @@ Bug fixes
   :py:class:`CFTimeIndex` now results in a :py:class:`pandas.TimedeltaIndex`
   instead of raising a ``TypeError`` (:issue:`2671`).  By `Spencer Clark
   <https://github.com/spencerkclark>`_.
+- backend_kwargs are no longer ignored when using open_dataset with pynio engine
+  (:issue:'2380')
+  By 'Jonathan Joyce <https://github.com/jonmjoyce>'_.
 - Fix ``open_rasterio`` creating a WKT CRS instead of PROJ.4 with
   ``rasterio`` 1.0.14+ (:issue:`2715`).
   By `David Hoese <https://github.com/djhoese`_.

xarray/backends/pynio_.py

@@ -45,13 +45,13 @@ class NioDataStore(AbstractDataStore):
     """Store for accessing datasets via PyNIO
     """
 
-    def __init__(self, filename, mode='r', lock=None):
+    def __init__(self, filename, mode='r', lock=None, **kwargs):
         import Nio
         if lock is None:
             lock = PYNIO_LOCK
         self.lock = ensure_lock(lock)
         self._manager = CachingFileManager(
-            Nio.open_file, filename, lock=lock, mode=mode)
+            Nio.open_file, filename, lock=lock, mode=mode, kwargs=kwargs)
         # xarray provides its own support for FillValue,
         # so turn off PyNIO's support for the same.
         self.ds.set_option('MaskedArrayMode', 'MaskedNever')

xarray/tests/test_backends.py

@@ -2546,6 +2546,12 @@ def open(self, path, **kwargs):
         with open_dataset(path, engine='pynio', **kwargs) as ds:
             yield ds
 
+    def test_kwargs(self):
+        kwargs = {'format': 'grib'}
+        path = os.path.join(os.path.dirname(__file__), 'data', 'example')
+        with backends.NioDataStore(path, **kwargs) as store:
+            assert store._manager._kwargs['format'] == 'grib'
+
     def save(self, dataset, path, **kwargs):
         return dataset.to_netcdf(path, engine='scipy', **kwargs)