Ignore bad cell_measures attributes (#294)

* Ignore bad cell_measures attributes

CMIP6 likes the "--OPT" value.

Closes #216

* Consolidate tests

* fixes

Author: dcherian

cf_xarray/accessor.py

@@ -1230,7 +1230,12 @@ def __repr__(self):
 
         def make_text_section(subtitle, attr, valid_values, default_keys=None):
 
-            vardict = getattr(self, attr, {})
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore")
+                try:
+                    vardict = getattr(self, attr, {})
+                except ValueError:
+                    vardict = {}
 
             star = " * "
             tab = len(star) * " "
@@ -1398,8 +1403,15 @@ def cell_measures(self) -> dict[str, list[str]]:
             ]
 
         keys = {}
-        for attr in all_attrs:
-            keys.update(parse_cell_methods_attr(attr))
+        for attr in set(all_attrs):
+            try:
+                keys.update(parse_cell_methods_attr(attr))
+            except ValueError:
+                warnings.warn(
+                    f"Ignoring bad cell_measures attribute: {attr}.",
+                    UserWarning,
+                    stacklevel=2,
+                )
         measures = {
             key: self._drop_missing_variables(_get_all(self._obj, key)) for key in keys
         }

cf_xarray/tests/test_accessor.py

@@ -608,21 +608,23 @@ def test_getitem_errors(obj):
         obj2.cf["X"]
 
 
-def test_getitem_ignores_bad_measure_attribute():
+def test_bad_cell_measures_attribute():
     air2 = airds.copy(deep=True)
-    air2.air.attrs["cell_measures"] = "asd"
+    air2.air.attrs["cell_measures"] = "--OPT"
     with pytest.warns(UserWarning):
         assert_identical(air2.air.drop_vars("cell_area"), air2.cf["air"])
-
-    with pytest.raises(ValueError):
-        air2.cf.cell_measures
-    with pytest.raises(ValueError):
-        air2.air.cf.cell_measures
+    with pytest.warns(UserWarning):
+        assert air2.cf.cell_measures == {}
+    with pytest.warns(UserWarning):
+        assert air2.air.cf.cell_measures == {}
     with pytest.raises(ValueError):
         air2.cf.get_associated_variable_names("air", error=True)
     with pytest.warns(UserWarning):
         air2.cf.get_associated_variable_names("air", error=False)
 
+    #  GH216
+    repr(air2.cf)
+
 
 def test_getitem_clash_standard_name():
     ds = xr.Dataset()
@@ -1496,18 +1498,18 @@ def test_missing_variables():
 
     # Bounds
     ds = mollwds.copy(deep=True)
-    ds = ds.drop("lon_bounds")
+    ds = ds.drop_vars("lon_bounds")
     assert ds.cf.bounds == {"lat": ["lat_bounds"], "latitude": ["lat_bounds"]}
 
     with pytest.raises(KeyError, match=r"No results found for 'longitude'."):
         ds.cf.get_bounds("longitude")
 
     # Cell measures
     ds = airds.copy(deep=True)
-    ds = ds.drop("cell_area")
+    ds = ds.drop_vars("cell_area")
     assert ds.cf.cell_measures == {}
 
     # Formula terms
     ds = vert.copy(deep=True)
-    ds = ds.drop("ap")
+    ds = ds.drop_vars("ap")
     assert ds.cf.formula_terms == {"lev": {"b": "b", "ps": "ps"}}