Allow grouping input cubes by date (instead of filename) for fix_metadata

esmvalcore/cmor/_fixes/fix.py

@@ -48,6 +48,16 @@
 class Fix:
     """Base class for dataset fixes."""
 
+    GROUP_CUBES_BY_DATE = False
+    """Flag for grouping cubes for fix_metadata.
+
+    Fixes are applied to each group element individually.
+
+    If ``False`` (default), group cubes by file. If ``True``, group cubes by
+    date.
+
+    """
+
     def __init__(
         self,
         vardef: VariableInfo,

esmvalcore/cmor/_fixes/native6/era5.py

@@ -3,6 +3,7 @@
 import datetime
 import logging
 
+import iris
 import numpy as np
 from cf_units import Unit
 from iris.cube import CubeList
@@ -433,6 +434,44 @@ def fix_metadata(self, cubes):
         return cubes
 
 
+class Rsut(Fix):
+    """Fixes for rsut."""
+
+    # Enable grouping cubes by date for fix_metadata since multiple variables
+    # from multiple files are needed
+    GROUP_CUBES_BY_DATE = True
+
+    def fix_metadata(self, cubes):
+        """Fix metadata.
+
+        Derive rsut as
+
+        rsut = rsdt - rsnt
+
+        with
+
+        rsut = TOA Outgoing Shortwave Radiation
+        rsdt = TOA Incoming Shortwave Radiation
+        rsnt = TOA Net Incoming Shortwave Radiation
+
+        """
+        rsdt_cube = cubes.extract_cube(
+            iris.NameConstraint(long_name="TOA incident solar radiation"),
+        )
+        rsnt_cube = cubes.extract_cube(
+            iris.NameConstraint(
+                long_name="Mean top net short-wave radiation flux",
+            ),
+        )
+        rsdt_cube = Rsdt(None).fix_metadata([rsdt_cube])[0]
+        rsdt_cube.convert_units(self.vardef.units)
+
+        rsdt_cube.data = rsdt_cube.core_data() - rsnt_cube.core_data()
+        rsdt_cube.attributes["positive"] = "up"
+
+        return iris.cube.CubeList([rsdt_cube])
+
+
 class Rss(Fix):
     """Fixes for Rss."""
 

esmvalcore/cmor/fix.py

@@ -16,9 +16,11 @@
 from iris.cube import Cube, CubeList
 
 from esmvalcore.cmor._fixes.fix import Fix
-from esmvalcore.io.local import LocalFile
+from esmvalcore.io.local import LocalFile, _get_start_end_date
 
 if TYPE_CHECKING:
+    from collections.abc import Iterable
+
     from esmvalcore.config import Session
 
 logger = logging.getLogger(__name__)
@@ -129,6 +131,27 @@ def fix_file(  # noqa: PLR0913
     return result
 
 
+def _group_cubes(fixes: Iterable[Fix], cubes: CubeList) -> dict[Any, CubeList]:
+    """Group cubes for fix_metadata; each group is processed individually."""
+    grouped_cubes: dict[Any, CubeList] = defaultdict(CubeList)
+
+    # Group by date
+    if any(fix.GROUP_CUBES_BY_DATE for fix in fixes):
+        for cube in cubes:
+            if "source_file" in cube.attributes:
+                dates = _get_start_end_date(cube.attributes["source_file"])
+            else:
+                dates = None
+            grouped_cubes[dates].append(cube)
+
+    # Group by file name
+    else:
+        for cube in cubes:
+            grouped_cubes[cube.attributes.get("source_file", "")].append(cube)
+
+    return grouped_cubes
+
+
 def fix_metadata(
     cubes: Sequence[Cube],
     short_name: str,
@@ -192,13 +215,14 @@ def fix_metadata(
     )
     fixed_cubes = CubeList()
 
-    # Group cubes by input file and apply all fixes to each group element
-    # (i.e., each file) individually
-    by_file = defaultdict(list)
-    for cube in cubes:
-        by_file[cube.attributes.get("source_file", "")].append(cube)
-
-    for group in by_file.values():
+    # Group cubes and apply all fixes to each group element individually. There
+    # are two options for grouping:
+    # (1) By input file name (default).
+    # (2) By time range (can be enabled by setting the attribute
+    #     GROUP_CUBES_BY_DATE=True for the fix class; see
+    #     _fixes.native6.era5.Rsut for an example).
+    grouped_cubes = _group_cubes(fixes, cubes)
+    for group in grouped_cubes.values():
         cube_list = CubeList(group)
         for fix in fixes:
             cube_list = fix.fix_metadata(cube_list)

tests/unit/cmor/test_fix.py

@@ -189,6 +189,7 @@ def setUp(self):
         self.cube = self._create_mock_cube()
         self.fixed_cube = self._create_mock_cube()
         self.mock_fix = Mock()
+        self.mock_fix.GROUP_CUBES_BY_DATE = False
         self.mock_fix.fix_metadata.return_value = [self.fixed_cube]
         self.expected_get_fixes_call = {
             "project": "project",