Add new h5netcdf backend phony_dims kwarg (#3753)

* ADD: add `phony_dims` keyword arg to h5netcdf backend available from h5netcdf v0.8.0

* ADD: add `whats-new.rst` entry

* FIX: raise ValueError

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

Author: kmuehlbauer

doc/whats-new.rst

@@ -24,9 +24,14 @@ Breaking changes
 
 New Features
 ~~~~~~~~~~~~
+
+- Support new h5netcdf backend keyword `phony_dims` (available from h5netcdf
+  v0.8.0 for :py:class:`~xarray.backends.H5NetCDFStore`.
+  By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_.
 - implement pint support. (:issue:`3594`, :pull:`3706`)
   By `Justus Magin <https://github.com/keewis>`_.
 
+
 Bug fixes
 ~~~~~~~~~
 - Use ``dask_array_type`` instead of ``dask_array.Array`` for type

xarray/backends/h5netcdf_.py

@@ -1,4 +1,5 @@
 import functools
+from distutils.version import LooseVersion
 
 import numpy as np
 
@@ -117,13 +118,22 @@ def open(
         lock=None,
         autoclose=False,
         invalid_netcdf=None,
+        phony_dims=None,
     ):
         import h5netcdf
 
         if format not in [None, "NETCDF4"]:
             raise ValueError("invalid format for h5netcdf backend")
 
         kwargs = {"invalid_netcdf": invalid_netcdf}
+        if phony_dims is not None:
+            if LooseVersion(h5netcdf.__version__) >= LooseVersion("0.8.0"):
+                kwargs["phony_dims"] = phony_dims
+            else:
+                raise ValueError(
+                    "h5netcdf backend keyword argument 'phony_dims' needs "
+                    "h5netcdf >= 0.8.0."
+                )
 
         if lock is None:
             if mode == "r":