Ignore overflow errors when converting branch times (#2668)

Co-authored-by: Valeriu Predoi <[email protected]>

Author: bouweandela

esmvalcore/cmor/_fixes/fix.py

@@ -831,15 +831,23 @@ def _fix_time_units(self, cube: Cube, cube_coord: Coord) -> None:
 
                     branch_parent = "branch_time_in_parent"
                     if branch_parent in attrs:
-                        attrs[branch_parent] = parent_units.convert(
-                            attrs[branch_parent], cube_coord.units
-                        )
+                        try:
+                            attrs[branch_parent] = parent_units.convert(
+                                attrs[branch_parent], cube_coord.units
+                            )
+                        except OverflowError:
+                            # This happens when the time is very large.
+                            pass
 
                     branch_child = "branch_time_in_child"
                     if branch_child in attrs:
-                        attrs[branch_child] = old_units.convert(
-                            attrs[branch_child], cube_coord.units
-                        )
+                        try:
+                            attrs[branch_child] = old_units.convert(
+                                attrs[branch_child], cube_coord.units
+                            )
+                        except OverflowError:
+                            # This happens when the time is very large.
+                            pass
 
     def _fix_time_bounds(self, cube: Cube, cube_coord: Coord) -> None:
         """Fix time bounds."""

tests/integration/cmor/test_fix.py

@@ -734,18 +734,42 @@ def test_fix_metadata_amon_tas_invalid_time_units(self):
         assert self.mock_debug.call_count == 3
         assert self.mock_warning.call_count == 7
 
-    def test_fix_metadata_amon_tas_invalid_time_attrs(self):
+    @pytest.mark.parametrize("problem", ["none", "bad_units", "bad_values"])
+    def test_fix_metadata_amon_tas_invalid_time_attrs(self, problem):
         """Test ``fix_metadata`` with invalid time attributes."""
         short_name = "tas"
         project = "CMIP6"
         dataset = "__MODEL_WITH_NO_EXPLICIT_FIX__"
         mip = "Amon"
 
-        self.cubes_2d_latlon[0].attributes = {
-            "parent_time_units": "this is certainly not a unit",
-            "branch_time_in_parent": "BRANCH TIME IN PARENT",
-            "branch_time_in_child": "BRANCH TIME IN CHILD",
-        }
+        attributes = {}
+        expected_attributes = {}
+        if problem == "bad_units":
+            attributes["parent_time_units"] = "this is certainly not a unit"
+        else:
+            attributes["parent_time_units"] = "days since 1000-01-01 00:00:0.0"
+
+        if problem == "bad_values":
+            attributes["branch_time_in_child"] = 1e9
+            attributes["branch_time_in_parent"] = 1e9
+        else:
+            attributes["branch_time_in_child"] = 0.0
+            attributes["branch_time_in_parent"] = 91676.0
+
+        if problem == "none":
+            expected_attributes = {
+                "parent_time_units": "days since 1850-1-1 00:00:00",
+                "branch_time_in_child": 365,
+                "branch_time_in_parent": -218574,
+            }
+        else:
+            expected_attributes = attributes.copy()
+        if problem == "bad_values":
+            expected_attributes["parent_time_units"] = (
+                "days since 1850-1-1 00:00:00"
+            )
+
+        self.cubes_2d_latlon[0].attributes = attributes
 
         fixed_cubes = fix_metadata(
             self.cubes_2d_latlon,
@@ -762,11 +786,7 @@ def test_fix_metadata_amon_tas_invalid_time_attrs(self):
         self.assert_lat_metadata(fixed_cube)
         self.assert_lon_metadata(fixed_cube)
 
-        assert fixed_cube.attributes == {
-            "parent_time_units": "this is certainly not a unit",
-            "branch_time_in_parent": "BRANCH TIME IN PARENT",
-            "branch_time_in_child": "BRANCH TIME IN CHILD",
-        }
+        assert fixed_cube.attributes == expected_attributes
 
         cmor_check_metadata(fixed_cube, project, mip, short_name)