test: add tests for case-insensitive lookup and skipping None shadowing in SQL queries

Author: kosiew

python/datafusion/context.py

@@ -784,13 +784,32 @@ def _lookup_python_object(name: str) -> Any | None:
         try:
             if frame is not None:
                 frame = frame.f_back
+            lower_name = name.lower()
+
+            def _match(mapping: dict[str, Any]) -> Any | None:
+                if not mapping:
+                    return None
+
+                value = mapping.get(name)
+                if value is not None:
+                    return value
+
+                for key, candidate in mapping.items():
+                    if isinstance(key, str) and key.lower() == lower_name:
+                        if candidate is not None:
+                            return candidate
+
+                return None
+
             while frame is not None:
                 locals_dict = frame.f_locals
-                if name in locals_dict:
-                    return locals_dict[name]
+                match = _match(locals_dict)
+                if match is not None:
+                    return match
                 globals_dict = frame.f_globals
-                if name in globals_dict:
-                    return globals_dict[name]
+                match = _match(globals_dict)
+                if match is not None:
+                    return match
                 frame = frame.f_back
         finally:
             del frame

python/tests/test_context.py

@@ -337,6 +337,31 @@ def run_query():
     assert result[0].column(0).to_pylist()[0] == 4
 
 
+def test_sql_auto_register_skips_none_shadowing():
+    ctx = SessionContext(auto_register_python_objects=True)
+    mytable = pa.Table.from_pydict({"value": [1, 2, 3]})  # noqa: F841
+
+    def run_query():
+        mytable = None  # noqa: F841
+        return ctx.sql(
+            "SELECT SUM(value) AS total FROM mytable",
+        ).collect()
+
+    batches = run_query()
+    assert batches[0].column(0).to_pylist()[0] == 6
+
+
+def test_sql_auto_register_case_insensitive_lookup():
+    ctx = SessionContext(auto_register_python_objects=True)
+    MyTable = pa.Table.from_pydict({"value": [2, 3]})  # noqa: F841
+
+    batches = ctx.sql(
+        "SELECT SUM(value) AS total FROM mytable",
+    ).collect()
+
+    assert batches[0].column(0).to_pylist()[0] == 5
+
+
 def test_sql_auto_register_pandas_dataframe():
     pd = pytest.importorskip("pandas")