feat: Add mask per param filter

src/anemoi/transform/filters/fields/apply_mask.py

@@ -15,7 +15,7 @@
 
 from anemoi.transform.fields import new_field_from_numpy
 from anemoi.transform.fields import new_fieldlist_from_list
-from anemoi.transform.filter import Filter
+from anemoi.transform.filter import SingleFieldFilter
 from anemoi.transform.filters import filter_registry
 
 LOG = logging.getLogger(__name__)
@@ -36,8 +36,7 @@
 }
 
 
-@filter_registry.register("apply_mask")
-class MaskVariable(Filter):
+class ApplyMaskMixin:
     """A filter to mask variables using an external file.
 
     The values of every filtered fields are set to NaN when they are either:
@@ -96,7 +95,7 @@ def __init__(
         ----------
         path : str
             Path to the external file containing the mask.
-        mask_value : int, optional
+        mask_value : float, optional
             Value to be used for masking, by default 1.
         threshold : float, optional
             Threshold value for masking, by default None.
@@ -121,31 +120,75 @@ def __init__(
 
         self._rename = rename
 
-    def forward(self, data: ekd.FieldList) -> ekd.FieldList:
+    def mask(self, data: ekd.Field) -> ekd.Field:
         """Apply the forward transformation to the data.
 
         Parameters
         ----------
-        data : ekd.FieldList
+        data : ekd.Field
             Input data to be transformed.
 
         Returns
         -------
-        ekd.FieldList
+        ekd.Field
             Transformed data.
         """
-        result = []
         extra = {}
-        for field in data:
 
-            values = field.to_numpy(flatten=True)
-            values[self._mask] = np.nan
+        values = data.to_numpy(flatten=True)
+        values[self._mask] = np.nan
+
+        if self._rename is not None:
+            param = data.metadata("param")
+            name = f"{param}_{self._rename}"
+            extra["param"] = name
 
-            if self._rename is not None:
-                param = field.metadata("param")
-                name = f"{param}_{self._rename}"
-                extra["param"] = name
+        return new_field_from_numpy(values, template=data, **extra)
 
-            result.append(new_field_from_numpy(values, template=field, **extra))
 
+@filter_registry.register("apply_mask")
+class MaskAllVariables(ApplyMaskMixin):
+    """A filter to mask all variables using an external file."""
+
+    def forward(self, data: ekd.FieldList) -> ekd.FieldList:
+        result = []
+        for field in data:
+            masked_field = self.mask(field)
+            result.append(masked_field)
         return new_fieldlist_from_list(result)
+
+
+@filter_registry.register("apply_mask_to_param")
+class ApplyMaskToParam(ApplyMaskMixin, SingleFieldFilter):
+    """A filter to mask a specific variable using an external file."""
+
+    required_inputs = ["param"]
+
+    def __init__(
+        self,
+        *,
+        param: str,
+        path: str,
+        mask_value: float | None = None,
+        threshold: float | None = None,
+        threshold_operator: (
+            Literal["<"] | Literal["<="] | Literal[">"] | Literal[">="] | Literal["=="] | Literal["!="]
+        ) = ">",
+        rename: str | None = None,
+    ):
+        SingleFieldFilter.__init__(self, param=param)
+        ApplyMaskMixin.__init__(
+            self,
+            path=path,
+            mask_value=mask_value,
+            threshold=threshold,
+            threshold_operator=threshold_operator,
+            rename=rename,
+        )
+        self.param = param
+
+    def forward_select(self):
+        return {"param": self.param}
+
+    def forward_transform(self, param: ekd.Field) -> ekd.Field:
+        return self.mask(param)

tests/field_filters/test_apply_mask.py

@@ -106,9 +106,70 @@ def test_apply_mask(source, ekd_from_source, mask_name, rename, threshold_option
             assert np.sum(np.isnan(result)) == expected_mask_count
 
 
-if __name__ == "__main__":
-    """Run all test functions that start with 'test_'."""
-    for name, obj in list(globals().items()):
-        if name.startswith("test_") and callable(obj):
-            print(f"Running {name}...")
-            obj()
+@pytest.mark.parametrize(
+    "threshold_options",
+    [
+        {"mask_value": 0.5},
+        {"mask_value": 1},
+        {"threshold": 0.5, "threshold_operator": ">"},
+        {"threshold": 0.5, "threshold_operator": "<"},
+    ],
+)
+@pytest.mark.parametrize("rename", [None, "renamed"])
+@pytest.mark.parametrize("mask_name", MASK_VALUES.keys())
+@pytest.mark.parametrize("target_param", DATA_VALUES.keys())
+def test_apply_mask_to_param(source, ekd_from_source, target_param, mask_name, rename, threshold_options):
+    apply_mask = filter_registry.create(
+        "apply_mask_to_param", param=target_param, path=mask_name, rename=rename, **threshold_options
+    )
+    ekd_from_source.assert_called_once_with("file", mask_name)
+
+    pipeline = source | apply_mask
+
+    input_fields = collect_fields_by_param(source)
+    output_fields = collect_fields_by_param(pipeline)
+
+    expected_mask = MASK_VALUES[mask_name].copy().flatten()
+    if "mask_value" in threshold_options:
+        expected_mask = expected_mask == threshold_options["mask_value"]
+    else:
+        operator = {"<": np.less, ">": np.greater}[threshold_options["threshold_operator"]]
+        expected_mask = operator(expected_mask, threshold_options["threshold"])
+    expected_mask_count = np.sum(expected_mask)
+
+    result_param = f"{target_param}_{rename}" if rename else target_param
+
+    # The target param should be masked (and possibly renamed)
+    assert result_param in output_fields
+    for input_field, output_field in zip(input_fields[target_param], output_fields[result_param]):
+        expected_values = input_field.to_numpy(flatten=True).copy()
+        expected_values[expected_mask] = np.nan
+        result = output_field.to_numpy(flatten=True)
+        np.array_equal(expected_values, result, equal_nan=True)
+        assert np.sum(np.isnan(result)) == expected_mask_count
+
+    # When renamed, the original param name must not appear in the output
+    if rename:
+        assert target_param not in output_fields
+
+    # All other params should pass through unchanged
+    for other_param in DATA_VALUES.keys():
+        if other_param == target_param:
+            continue
+        assert other_param in output_fields
+        for input_field, output_field in zip(input_fields[other_param], output_fields[other_param]):
+            np.testing.assert_array_equal(
+                input_field.to_numpy(flatten=True),
+                output_field.to_numpy(flatten=True),
+            )
+
+
+def test_apply_mask_to_param_fails_without_param(ekd_from_source):
+    with pytest.raises((ValueError, TypeError)):
+        filter_registry.create("apply_mask_to_param", path="all_zeros", mask_value=1)
+
+
+def test_apply_mask_to_param_fails_without_mask_options(ekd_from_source):
+    with pytest.raises(ValueError):
+        filter_registry.create("apply_mask_to_param", param="t", path="all_zeros")
+        ekd_from_source.assert_called_once_with("file", "all_zeros")