Fix grib field serialisation (#812)

* Fix grib field serialisation

Author: sandorkertesz

docs/release_notes/version_0.16_updates.rst

@@ -1,6 +1,16 @@
 Version 0.16 Updates
 /////////////////////////
 
+
+Version 0.16.7
+===============
+
+Fixes
+++++++++
+
+- Fixed issue when the serialisation of a GRIB field loaded from disk did not work (:pr:`812`)
+
+
 Version 0.16.6
 ===============
 

src/earthkit/data/readers/grib/codes.py

@@ -356,7 +356,7 @@ def clone(self, **kwargs):
         return ClonedGribField(self, **kwargs)
 
     def __getstate__(self):
-        state = super().__getstate__()
+        state = dict()
         state["path"] = self.path
         state["offset"] = self._offset
         state["length"] = self._length

tests/grib/test_grib_serialise.py

@@ -60,6 +60,19 @@ def test_grib_serialise_metadata(fl_type, representation):
         assert md[k] == md2[k]
 
 
+@pytest.mark.parametrize("fl_type", FL_NUMPY)
+@pytest.mark.parametrize("representation", ["file", "memory"])
+def test_grib_serialise_field(fl_type, representation):
+    ds, _ = load_grib_data("test.grib", fl_type)
+    f = ds[0]
+
+    f2 = _pickle(f, representation)
+
+    keys = ["param", "date", "time", "step", "level", "gridType", "type"]
+    for k in keys:
+        assert f.metadata(k) == f2.metadata(k)
+
+
 @pytest.mark.parametrize("representation", ["file", "memory"])
 def test_grib_serialise_standalone_metadata(representation):
     ds = from_source("file", earthkit_examples_file("test.grib"))