Add option to disable warnings about missing variables (#304)

Author: dcherian

cf_xarray/accessor.py

@@ -1526,10 +1526,11 @@ def get_associated_variable_names(
         allvars = itertools.chain(*coords.values())
         missing = set(allvars) - set(self._maybe_to_dataset().variables)
         if missing:
-            warnings.warn(
-                f"Variables {missing!r} not found in object but are referred to in the CF attributes.",
-                UserWarning,
-            )
+            if OPTIONS["warn_on_missing_variables"]:
+                warnings.warn(
+                    f"Variables {missing!r} not found in object but are referred to in the CF attributes.",
+                    UserWarning,
+                )
             for k, v in coords.items():
                 for m in missing:
                     if m in v:

cf_xarray/options.py

@@ -9,6 +9,7 @@
 
 OPTIONS: MutableMapping[str, Any] = {
     "custom_criteria": [],
+    "warn_on_missing_variables": True,
 }
 
 
@@ -20,6 +21,9 @@ class set_options:
     custom_criteria : dict
         Translate from axis, coord, or custom name to
         variable name optionally using ``custom_criteria``. Default: [].
+    warn_on_missing_variables : bool
+        Whether to raise a warning when variables referred to in attributes
+        are not present in the object.
 
     Examples
     --------

cf_xarray/tests/test_accessor.py

@@ -299,6 +299,11 @@ def test_getitem_ancillary_variables():
     with pytest.warns(UserWarning):
         anc[["q"]].cf["q"]
 
+    with pytest.warns(None) as record:
+        with cf_xarray.set_options(warn_on_missing_variables=False):
+            anc[["q"]].cf["q"]
+            assert len(record) == 0
+
     for k in ["ULONG", "ULAT"]:
         assert k not in popds.cf["TEMP"].coords