From e672cbfe0afbc62c57dd2e5fef4b5bf3604a0b31 Mon Sep 17 00:00:00 2001
From: Aarab Malik <178716638+aarab-malik@users.noreply.github.com>
Date: Wed, 11 Nov 2026 09:36:26 +0000
Subject: [PATCH] fix: Allow NaN in bounded float columns when allow_nan is set

Bound comparisons reject NaN, so allow_nan was ignored once min or max
was set. Accept NaN in those rules and leave the decision to allow_nan.
---
 dataframely/columns/float.py     |   8 +++
 tests/column_types/test_float.py | 101 ++++++++++++++++++++++++++++++-
 2 files changed, 108 insertions(+), 1 deletion(-)

diff --git a/dataframely/columns/float.py b/dataframely/columns/float.py
index 82e29b51..e1d4bc25 100644
--- a/dataframely/columns/float.py
+++ b/dataframely/columns/float.py
@@ -150,6 +150,14 @@ def validation_rules(self, expr: pl.Expr) -> dict[str, pl.Expr]:
             result["inf"] = ~expr.is_infinite()
         if not self.allow_nan:
             result["nan"] = ~expr.is_nan()
+        else:
+            # Ordered comparisons do not accept NaN. Polars ranks NaN above every
+            # number, so upper bounds reject it while lower bounds do not. When NaN
+            # is allowed, bound rules must pass it through and leave the decision
+            # to `allow_nan`.
+            for name in ("min", "min_exclusive", "max", "max_exclusive"):
+                if name in result:
+                    result[name] = result[name] | expr.is_nan()
         return result
 
     def _sample_unchecked(self, generator: Generator, n: int) -> pl.Series:
diff --git a/tests/column_types/test_float.py b/tests/column_types/test_float.py
index cc0a1f70..9e03075a 100644
--- a/tests/column_types/test_float.py
+++ b/tests/column_types/test_float.py
@@ -13,7 +13,12 @@
 
 import dataframely as dy
 from dataframely.columns.float import _BaseFloat
-from dataframely.testing import FLOAT_COLUMN_TYPES, evaluate_rules, rules_from_exprs
+from dataframely.testing import (
+    FLOAT_COLUMN_TYPES,
+    create_schema,
+    evaluate_rules,
+    rules_from_exprs,
+)
 
 
 class IntegerSchema(dy.Schema):
@@ -186,6 +191,100 @@ def test_validate_allow_inf_nan(inf: Any, nan: Any) -> None:
     )
 
 
+@pytest.mark.parametrize("column_type", FLOAT_COLUMN_TYPES)
+@pytest.mark.parametrize(
+    ("bound", "threshold", "inside", "outside"),
+    [
+        ("min", 0.0, 1.0, -1.0),
+        ("min_exclusive", 0.0, 1.0, 0.0),
+        ("max", 10.0, 1.0, 11.0),
+        ("max_exclusive", 10.0, 1.0, 10.0),
+    ],
+)
+@pytest.mark.parametrize("allow_nan", [True, False])
+def test_validate_nan_with_bounds(
+    column_type: type[_BaseFloat],
+    bound: str,
+    threshold: float,
+    inside: float,
+    outside: float,
+    allow_nan: bool,
+) -> None:
+    # Arrange
+    kwargs: dict[str, Any] = {
+        bound: threshold,
+        "allow_nan": allow_nan,
+        "nullable": True,
+    }
+    column = column_type(**kwargs)
+    values = pl.Series([float("nan"), inside, outside, None], dtype=pl.Float64).cast(
+        column.dtype
+    )
+    lf = pl.LazyFrame({"a": values})
+    schema = create_schema("test", {"a": column})
+
+    # Act
+    actual = evaluate_rules(
+        lf, rules_from_exprs(column.validation_rules(pl.col("a")))
+    ).collect()
+    good, failure = schema.filter(lf.collect())
+
+    # Assert
+    assert actual[bound].to_list()[1:] == [True, False, True]
+    if allow_nan:
+        assert actual[bound][0] is True
+        assert "nan" not in actual.columns
+        assert good.height == 3
+        assert good.get_column("a").is_nan().sum() == 1
+        assert failure.counts() == {f"a|{bound}": 1}
+    else:
+        assert actual["nan"].to_list() == [False, True, True, True]
+        assert good.height == 2
+        assert good.get_column("a").is_nan().sum() == 0
+        assert failure.counts()["a|nan"] == 1
+        assert failure.counts()[f"a|{bound}"] >= 1
+
+
+@pytest.mark.parametrize("column_type", FLOAT_COLUMN_TYPES)
+@pytest.mark.parametrize(
+    "kwargs",
+    [
+        {"min": 0.0},
+        {"min_exclusive": 0.0},
+        {"max": 10.0},
+        {"max_exclusive": 10.0},
+        {"min": 0.0, "max": 10.0},
+    ],
+)
+def test_sample_nan_with_bounds_is_valid(
+    column_type: type[_BaseFloat], kwargs: dict[str, Any]
+) -> None:
+    # Arrange
+    column = column_type(**kwargs, allow_nan=True)
+    schema = create_schema("test", {"a": column})
+
+    # Act
+    sampled = schema.sample(10_000, generator=dy.random.Generator(0))
+
+    # Assert
+    nan_count = sampled.get_column("a").is_nan().sum()
+    assert 0.01 * sampled.height < nan_count < 0.1 * sampled.height
+    schema.validate(sampled)
+
+
+def test_list_float_nan_with_max() -> None:
+    # Arrange
+    schema = create_schema("test", {"a": dy.List(dy.Float64(max=10.0, allow_nan=True))})
+    df = pl.DataFrame({"a": [[1.0, float("nan")], [1.0, 11.0], [float("nan")]]})
+
+    # Act
+    good, failure = schema.filter(df)
+
+    # Assert
+    assert good.height == 2
+    assert failure.counts() == {"a|inner_max": 1}
+
+
 def test_sample_unchecked_min_0() -> None:
     column = dy.Float(min=0, max=10)
     actual = column._sample_unchecked(dy.random.Generator(), n=10000)