Enable callbacks for loading netcdf with multiple variables

lib/iris/fileformats/netcdf/loader.py

@@ -592,7 +592,7 @@ def _translate_constraints_to_var_callback(constraints):
 
     Notes
     -----
-    For now, ONLY handles a single NameConstraint with no 'STASH' component.
+    For now, ONLY handles NameConstraints with no 'STASH' component.
 
     """
     import iris._constraints
@@ -624,6 +624,34 @@ def inner(cf_datavar):
                             break
                 return match
 
+            result = inner
+    elif len(constraints) > 1:
+        if all(
+            isinstance(constraint, iris._constraints.NameConstraint)
+            and constraint.STASH == "none"
+            for constraint in constraints
+        ):
+
+            def inner(cf_datavar):
+                match = False
+                for constraint in constraints:
+                    match = True
+                    for name in constraint._names:
+                        expected = getattr(constraint, name)
+                        if name != "STASH" and expected != "none":
+                            attr_name = "cf_name" if name == "var_name" else name
+                            # Fetch property : N.B. CFVariable caches the property values
+                            # The use of a default here is the only difference from the code in NameConstraint.
+                            if not hasattr(cf_datavar, attr_name):
+                                continue
+                            actual = getattr(cf_datavar, attr_name, "")
+                            if actual != expected:
+                                match = False
+                                break
+                    if match:
+                        break
+                return match
+
             result = inner
     return result
 

lib/iris/tests/unit/fileformats/netcdf/loader/test__translate_constraints_to_var_callback.py

@@ -33,7 +33,16 @@ class Test(tests.IrisTest):
     def test_multiple_constraints(self):
         constrs = [
             iris.NameConstraint(standard_name="x_wind"),
-            iris.NameConstraint(var_name="var1"),
+            iris.NameConstraint(var_name="var2"),
+        ]
+        callback = _translate_constraints_to_var_callback(constrs)
+        result = [callback(var) for var in self.data_variables]
+        self.assertArrayEqual(result, [True, True, False, True, False])
+
+    def test_multiple_constraints_invalid(self):
+        constrs = [
+            iris.NameConstraint(standard_name="x_wind"),
+            iris.NameConstraint(var_name="var1", STASH="m01s00i024"),
         ]
         result = _translate_constraints_to_var_callback(constrs)
         self.assertIsNone(result)