Support the new compression argument in netCDF4 > 1.6.0 (pydata#6981)

* Added support for the new compression argument in netCDF4 > 1.6.0

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Check both netCDF4 and libnetcdf versions to see if they support the new
compression arguments.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Remove checking netCDF4 and libnetcdf versions. We let them fail if they do not match compression/zlib arguments.

* Added test after merging with the new version of the file.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

xarray/backends/netCDF4_.py

@@ -232,11 +232,11 @@ def _extract_nc4_variable_encoding(
         "shuffle",
         "_FillValue",
         "dtype",
+        "compression",
     }
     if lsd_okay:
         valid_encodings.add("least_significant_digit")
     if h5py_okay:
-        valid_encodings.add("compression")
         valid_encodings.add("compression_opts")
 
     if not raise_on_invalid and encoding.get("chunksizes") is not None:

xarray/tests/test_backends.py

@@ -5068,6 +5068,12 @@ def test_extract_nc4_variable_encoding(self) -> None:
         encoding = _extract_nc4_variable_encoding(var, unlimited_dims=("x",))
         assert {} == encoding
 
+    @requires_netCDF4
+    def test_extract_nc4_variable_encoding_netcdf4(self, monkeypatch):
+        # New netCDF4 1.6.0 compression argument.
+        var = xr.Variable(("x",), [1, 2, 3], {}, {"compression": "szlib"})
+        _extract_nc4_variable_encoding(var, backend="netCDF4", raise_on_invalid=True)
+
     def test_extract_h5nc_encoding(self) -> None:
         # not supported with h5netcdf (yet)
         var = xr.Variable(("x",), [1, 2, 3], {}, {"least_sigificant_digit": 2})