fix(metrics): make convert_types handle pd.NA / pd.NaT (#1844)

src/evidently/core/metric_types.py

@@ -564,8 +564,24 @@ def convert_types(val):
         return int(val)
     if isinstance(val, str):
         return val
-    if val is None or np.isnan(val):
+    # `pd.NA` / `pd.NaT` reach here when label values come from nullable pandas
+    # dtypes (e.g. "string", "Int64"). `np.isnan(pd.NA)` raises TypeError
+    # ("boolean value of NA is ambiguous"); `pd.isna` safely covers all
+    # NA flavors (None, NaN, NaT, NA). We return None — these can't survive
+    # downstream as dict keys for ByLabelCountValue anyway, and the existing
+    # numpy-NaN call site already relied on returning a NA-shaped value here.
+    if val is None:
         return val
+    try:
+        if pd.isna(val):
+            # Preserve numpy.nan as-is (back-compat for the existing
+            # ByLabelCountValue serializer that turns it into the string
+            # "nan"); collapse pandas-flavored NA to None.
+            if isinstance(val, float):
+                return val
+            return None
+    except (TypeError, ValueError):
+        pass
     raise ValueError(f"type {type(val)} not supported as Label")
 
 

tests/future/test_metric_types.py

@@ -1,8 +1,10 @@
 import numpy as np
+import pandas as pd
 import pytest
 
 from evidently.core.metric_types import ByLabelCountValue
 from evidently.core.metric_types import SingleValue
+from evidently.core.metric_types import convert_types
 
 
 @pytest.mark.parametrize(
@@ -20,3 +22,46 @@ def test_by_label_count_value(input: dict, output: tuple):
         tests=[],
     )
     assert {"counts": output[0], "shares": output[1]} == value.to_simple_dict()
+
+
+@pytest.mark.parametrize(
+    "value",
+    [
+        pd.NA,
+        pd.NaT,
+    ],
+)
+def test_convert_types_handles_pandas_na(value):
+    # Regression for #1844: convert_types previously called np.isnan(val) which
+    # raises TypeError on pd.NA ("boolean value of NA is ambiguous") and on
+    # pd.NaT. Pandas-flavored NA should now collapse to None instead of
+    # propagating a TypeError up through ByLabelCountValue construction.
+    assert convert_types(value) is None
+
+
+def test_convert_types_preserves_existing_contracts():
+    # Non-NA labels must still flow through untouched, and numpy.nan must
+    # round-trip as a float so the ByLabelCountValue serializer keeps emitting
+    # the string "nan" (see test_by_label_count_value above).
+    assert convert_types(True) is True
+    assert convert_types(0) == 0
+    assert convert_types(42) == 42
+    assert convert_types("class_a") == "class_a"
+    assert convert_types(None) is None
+    nan_out = convert_types(np.nan)
+    assert isinstance(nan_out, float) and np.isnan(nan_out)
+
+
+def test_by_label_count_value_handles_pd_na_key():
+    # End-to-end: ByLabelCountValue construction must not crash when a count
+    # dict keyed by pd.NA reaches the convert_types pipeline.
+    value = ByLabelCountValue(
+        counts={pd.NA: SingleValue(value=1.0, display_name="t", metric_value_location=None)},
+        shares={pd.NA: SingleValue(value=1.0, display_name="t", metric_value_location=None)},
+        display_name="t",
+        metric_value_location=None,
+        tests=[],
+    )
+    # No assertion on key shape — just that construction + dict export succeed.
+    out = value.to_simple_dict()
+    assert "counts" in out and "shares" in out