refactor: compare calendars via helper

Co-authored-by: ilaflott <6273252+ilaflott@users.noreply.github.com>

Author: Codex

fremorizer/cmor_helpers.py

@@ -80,6 +80,19 @@ def normalize_calendar(calendar: Optional[str]) -> Optional[str]:
     calendar_lc = str(calendar).lower()
     return CF_CALENDAR_ALIASES.get(calendar_lc, calendar_lc)
 
+def calendars_are_equivalent(cal1: Optional[str], cal2: Optional[str]) -> bool:
+    """
+    Return True if two CF calendar names refer to the same calendar, accounting for aliases.
+
+    :param cal1: First CF calendar name (case-insensitive).
+    :type cal1: str, optional
+    :param cal2: Second CF calendar name (case-insensitive).
+    :type cal2: str, optional
+    :return: True if both names refer to the same calendar, False otherwise.
+    :rtype: bool
+    """
+    return normalize_calendar(cal1) == normalize_calendar(cal2)
+
 def get_time_calendar_value(time_var) -> Optional[str]:
     """
     Read a time variable's calendar/calendar_type attribute and normalize aliases.

fremorizer/cmor_mixer.py

@@ -200,11 +200,12 @@ def rewrite_netcdf_file_var( mip_var_cfgs: dict = None,
                            "this output could have the wrong calendar!")
     else:
         with open(json_exp_config, "r", encoding="utf-8") as file:
-            exp_cfg_calendar = normalize_calendar(json.load(file)['calendar'])
-            normalized_time_calendar = normalize_calendar(time_coords_calendar)
-            if normalized_time_calendar != exp_cfg_calendar:
-                raise ValueError(f"data calendar type {normalized_time_calendar} "
-                                 f"does not match input config calendar type: {exp_cfg_calendar}")
+            exp_cfg_calendar = json.load(file)['calendar']
+            if not calendars_are_equivalent(time_coords_calendar, exp_cfg_calendar):
+                norm_time = normalize_calendar(time_coords_calendar)
+                norm_cfg = normalize_calendar(exp_cfg_calendar)
+                raise ValueError(f"data calendar type {norm_time} "
+                                 f"does not match input config calendar type: {norm_cfg}")
 
     # read in time_bnds, if present
     fre_logger.info('attempting to read coordinate BNDS, time_bnds')

fremorizer/tests/test_cmor_helpers_update_calendar.py

@@ -141,6 +141,12 @@ def test_normalize_calendar_aliases_and_passthrough():
     assert normalize_calendar("julian") == "julian"
     assert normalize_calendar("CustomCalendar") == "customcalendar"
     assert normalize_calendar(None) is None
+    assert calendars_are_equivalent("noleap", "365_day") is True
+    assert calendars_are_equivalent("standard", "gregorian") is True
+    assert calendars_are_equivalent("all_leap", "366_day") is True
+    assert calendars_are_equivalent("julian", "julian") is True
+    assert calendars_are_equivalent("unknown", "unknown") is True
+    assert calendars_are_equivalent("unknown", "gregorian") is False
 
 
 class _FakeTime: