test: add test that NaNs in pyarrow tables roundtrip

ibis/backends/tests/conftest.py

@@ -78,3 +78,10 @@ def decorator(func):
     pytest.mark.notimpl(["datafusion", "exasol", "mssql", "druid", "oracle"]),
 ]
 NO_JSON_SUPPORT = combine_marks(NO_JSON_SUPPORT_MARKS)
+
+NAN_TREATED_AS_NULL_MARKS = [
+    pytest.mark.never(
+        ["sqlite", "mssql", "mysql"], reason="Treats NaN as NULL", raises=Exception
+    ),
+]
+NAN_TREATED_AS_NULL = combine_marks(NAN_TREATED_AS_NULL_MARKS)

ibis/backends/tests/test_pyarrow.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+import math
+
+import pytest
+
+import ibis
+from ibis.backends.tests.conftest import NAN_TREATED_AS_NULL
+
+pa = pytest.importorskip("pyarrow")
+
+
+@NAN_TREATED_AS_NULL
+@pytest.mark.notimpl(
+    "exasol", reason="Exasol driver can't handle NaNs during memtable registration"
+)
+@pytest.mark.parametrize(
+    "method",
+    [
+        pytest.param(lambda pa_arr: pa.table({"f": pa_arr}), id="pa_table"),
+        pytest.param(
+            lambda pa_arr: {"f": pa_arr},
+            id="dict_of_pa_arrays",
+            marks=pytest.mark.xfail(
+                # https://github.com/ibis-project/ibis/issues/11700
+                reason="During ops.InMemoryTable creation, we go through pd.DataFrame, losing NaN info"
+            ),
+        ),
+    ],
+)
+def test_nans_roundtrip(con, method):
+    inp = [1.0, float("nan"), None]
+    t = ibis.memtable(method(pa.array(inp)))
+    assert t.schema()["f"] == ibis.dtype("float64")
+
+    def make_comparable(vals):
+        return {"nan" if (isinstance(v, float) and math.isnan(v)) else v for v in vals}
+
+    n_nan = con.execute(t.f.isnan().sum())
+    n_null = con.execute(t.f.isnull().sum())
+    assert (n_nan, n_null) == (1, 1)
+
+    result = make_comparable(con.to_pyarrow(t.f).to_pylist())
+    expected = make_comparable(inp)
+    assert result == expected