test(datafusion-datatypes): test recursive conversion

ibis/backends/datafusion/tests/test_datatypes.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+import hypothesis as h
+
+import ibis.tests.strategies as its
+from ibis.backends.datafusion import as_nullable
+
+
+def is_nullable(dtype):
+    if dtype.is_struct():
+        return all(map(is_nullable, dtype.values()))
+    elif dtype.is_array():
+        return is_nullable(dtype.value_type)
+    elif dtype.is_map():
+        return is_nullable(dtype.key_type) and is_nullable(dtype.value_type)
+    else:
+        return dtype.nullable is True
+
+
+@h.given(its.all_dtypes())
+def test_as_nullable(dtype):
+    nullable_dtype = as_nullable(dtype)
+    assert nullable_dtype.nullable is True
+    assert is_nullable(nullable_dtype)