Raise error if weights are used with unweighted aggregator (#2640)

Author: schlunma

esmvalcore/preprocessor/_area.py

@@ -354,7 +354,12 @@ def area_statistics(
     # Get aggregator and correct kwargs (incl. weights)
     (agg, agg_kwargs) = get_iris_aggregator(operator, **operator_kwargs)
     agg_kwargs = update_weights_kwargs(
-        agg, agg_kwargs, "cell_area", cube, try_adding_calculated_cell_area
+        operator,
+        agg,
+        agg_kwargs,
+        "cell_area",
+        cube,
+        try_adding_calculated_cell_area,
     )
 
     with ignore_iris_vague_metadata_warnings():

esmvalcore/preprocessor/_shared.py

@@ -92,7 +92,7 @@ def get_iris_aggregator(
     x_coord = DimCoord([1.0], bounds=[0.0, 2.0], var_name="x")
     cube = Cube([0.0], dim_coords_and_dims=[(x_coord, 0)])
     test_kwargs = update_weights_kwargs(
-        aggregator, aggregator_kwargs, np.array([1.0])
+        operator, aggregator, aggregator_kwargs, np.array([1.0])
     )
     try:
         with ignore_iris_vague_metadata_warnings():
@@ -127,6 +127,7 @@ def aggregator_accept_weights(aggregator: iris.analysis.Aggregator) -> bool:
 
 
 def update_weights_kwargs(
+    operator: str,
     aggregator: iris.analysis.Aggregator,
     kwargs: dict,
     weights: Any,
@@ -138,6 +139,8 @@ def update_weights_kwargs(
 
     Parameters
     ----------
+    operator:
+        Named operator.
     aggregator:
         Iris aggregator.
     kwargs:
@@ -161,6 +164,10 @@ def update_weights_kwargs(
 
     """
     kwargs = dict(kwargs)
+    if not aggregator_accept_weights(aggregator) and "weights" in kwargs:
+        raise ValueError(
+            f"Aggregator '{operator}' does not support 'weights' option"
+        )
     if aggregator_accept_weights(aggregator) and kwargs.get("weights", True):
         kwargs["weights"] = weights
         if cube is not None and callback is not None:

esmvalcore/preprocessor/_time.py

@@ -836,7 +836,12 @@ def climate_statistics(
     if period in ("full",):
         (agg, agg_kwargs) = get_iris_aggregator(operator, **operator_kwargs)
         agg_kwargs = update_weights_kwargs(
-            agg, agg_kwargs, "_time_weights_", cube, _add_time_weights_coord
+            operator,
+            agg,
+            agg_kwargs,
+            "_time_weights_",
+            cube,
+            _add_time_weights_coord,
         )
         with warnings.catch_warnings():
             warnings.filterwarnings(

esmvalcore/preprocessor/_volume.py

@@ -293,6 +293,7 @@ def volume_statistics(
 
     (agg, agg_kwargs) = get_iris_aggregator(operator, **operator_kwargs)
     agg_kwargs = update_weights_kwargs(
+        operator,
         agg,
         agg_kwargs,
         "ocean_volume",
@@ -377,6 +378,7 @@ def axis_statistics(
     # bounds of the original coordinate (this handles units properly, e.g., for
     # sums)
     agg_kwargs = update_weights_kwargs(
+        operator,
         agg,
         agg_kwargs,
         "_axis_statistics_weights_",

tests/unit/preprocessor/test_shared.py

@@ -66,13 +66,12 @@ def test_get_iris_aggregator_mean(operator, kwargs):
     assert agg_kwargs == kwargs
 
 
-@pytest.mark.parametrize("kwargs", [{}, {"weights": True}])
 @pytest.mark.parametrize("operator", ["median", "mEdIaN", "MEDIAN"])
-def test_get_iris_aggregator_median(operator, kwargs):
+def test_get_iris_aggregator_median(operator):
     """Test ``get_iris_aggregator``."""
-    (agg, agg_kwargs) = get_iris_aggregator(operator, **kwargs)
+    (agg, agg_kwargs) = get_iris_aggregator(operator)
     assert agg == iris.analysis.MEDIAN
-    assert agg_kwargs == kwargs
+    assert agg_kwargs == {}
 
 
 @pytest.mark.parametrize("operator", ["min", "MiN", "MIN"])
@@ -172,6 +171,14 @@ def test_get_iris_aggregator_missing_kwarg():
         get_iris_aggregator("percentile")
 
 
+def test_get_iris_aggregator_no_weights_allowed():
+    """Test ``get_iris_aggregator``."""
+    operator = "median"
+    kwargs = {"weights": True}
+    with pytest.raises(ValueError):
+        get_iris_aggregator(operator, **kwargs)
+
+
 @pytest.mark.parametrize(
     "aggregator,result",
     [