Merge pull request #1003 from benjwadams/add_time_coordinate_calendar…

…_check

[CF 1.9] Ensure time coordinate variables have a calendar attribute s…

compliance_checker/cf/cf_1_6.py

@@ -2221,7 +2221,7 @@ def check_grid_coordinates(self, ds):
 
             alt = (
                 "{} has no coordinate associated with a variable identified as true latitude/longitude; "
-                + "its coordinate variable should also share a subset of {}'s dimensions"
+                "its coordinate variable should also share a subset of {}'s dimensions"
             )
 
             # Make sure we can find latitude and its dimensions are a subset

compliance_checker/cf/cf_1_9.py

@@ -1,5 +1,6 @@
 from netCDF4 import Dataset
 
+from compliance_checker import cfutil
 from compliance_checker.base import BaseCheck, TestCtx
 from compliance_checker.cf.cf_1_8 import CF1_8Check
 from compliance_checker.cf.util import VariableReferenceError, reference_attr_variables
@@ -13,6 +14,31 @@ def __init__(self, options=None):
         super(CF1_9Check, self).__init__(options)
         self.section_titles.update({"5.8": "§5.8 Domain Variables"})
 
+    def check_calendar(self, ds):
+        # IMPLEMENTATION CONFORMANCE 4.4.1 RECOMMENDED CF 1.9
+        super(CF1_9Check, self).check_calendar.__doc__
+        prev_return = super(CF1_9Check, self).check_calendar(ds)
+        time_var_candidate_name = cfutil.get_time_variable(ds)
+        time_var_name = (
+            time_var_candidate_name
+            if time_var_candidate_name in self._find_coord_vars(ds)
+            else None
+        )
+        # most datasets should have a time coordinate variable
+        test_ctx = self.get_test_ctx(
+            BaseCheck.HIGH, self.section_titles["4.4"], time_var_name
+        )
+        if time_var_name is None:
+            return prev_return
+
+        test_ctx.assert_true(
+            hasattr(ds.variables[time_var_name], "calendar"),
+            f'Time coordinate variable "{time_var_name}" '
+            "should have a calendar attribute",
+        )
+        prev_return.append(test_ctx.to_result())
+        return prev_return
+
     def check_domain_variables(self, ds: Dataset):
         # Domain variables should have coordinates attribute, but should have
         # scalar dimensions

compliance_checker/tests/test_cf.py

@@ -2997,6 +2997,30 @@ class TestCF1_9(BaseTestCase):
     def setUp(self):
         self.cf = CF1_9Check()
 
+    def test_time_variable_has_calendar(self):
+        # TEST CONFORMANCE 4.4.1 RECOMMENDED CF 1.9
+        dataset = MockTimeSeries()
+        results = self.cf.check_calendar(dataset)
+        assert (
+            results[0].msgs[0] == 'Time coordinate variable "time" should have a '
+            "calendar attribute"
+        )
+        # FIXME: NetCDF files shouldn't normally be modified so we can usually
+        # depend on cached results. Here we need to recreate the checker
+        # instance in order to not have previous results included pass condition
+        self.cf = CF1_9Check()
+        dataset.variables["time"].calendar = "standard"
+        results = self.cf.check_calendar(dataset)
+        # no time coordinate present, i.e. there is no time variable name with
+        # the same name as the time dimension name.
+        self.cf = CF1_9Check()
+        dataset = MockTimeSeries()
+        dataset.variables["time2"] = dataset.variables["time"]
+        del dataset.variables["time"]
+        results = self.cf.check_calendar(dataset)
+        # results array should be empty as no time coordinate variable detected
+        assert not results
+
     def test_domain(self):
         dataset = MockTimeSeries()
         domain_var = dataset.createVariable("domain", "c", ())