test: add test that NaNs in pyarrow tables roundtrip

Author: NickCrews

ibis/backends/tests/test_pyarrow.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import math
+
+import pytest
+
+import ibis
+
+pa = pytest.importorskip("pyarrow")
+
+
+@pytest.mark.notimpl(
+    "sqlite",
+    "During memtable registration, the pa.Table is converted to a pandas DataFrame, losing NaN info",
+)
+@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)))
+
+    def make_comparable(vals):
+        return {"nan" if (isinstance(v, float) and math.isnan(v)) else v for v in vals}
+
+    result = make_comparable(con.to_pyarrow(t.f).to_pylist())
+    expected = make_comparable(inp)
+    assert result == expected