From a5035bd016ad89121bc528d547bfbc9e74880799 Mon Sep 17 00:00:00 2001
From: "Jorge C. Leitao" <jorgecarleitao@gmail.com>
Date: Thu, 22 Jul 2021 18:33:24 +0000
Subject: [PATCH] Fixed nested FFI.

---
 .../tests/test_sql.py                         | 54 ++++++++++++++-----
 src/ffi/array.rs                              | 21 ++++++++
 src/ffi/ffi.rs                                |  4 +-
 3 files changed, 63 insertions(+), 16 deletions(-)

diff --git a/arrow-pyarrow-integration-testing/tests/test_sql.py b/arrow-pyarrow-integration-testing/tests/test_sql.py
index 2da732b746a..c3b6e7843a1 100644
--- a/arrow-pyarrow-integration-testing/tests/test_sql.py
+++ b/arrow-pyarrow-integration-testing/tests/test_sql.py
@@ -24,12 +24,17 @@
 
 class TestCase(unittest.TestCase):
     def setUp(self):
-        self.old_allocated_rust = arrow_pyarrow_integration_testing.total_allocated_bytes()
+        self.old_allocated_rust = (
+            arrow_pyarrow_integration_testing.total_allocated_bytes()
+        )
         self.old_allocated_cpp = pyarrow.total_allocated_bytes()
 
     def tearDown(self):
         # No leak of Rust
-        self.assertEqual(self.old_allocated_rust, arrow_pyarrow_integration_testing.total_allocated_bytes())
+        self.assertEqual(
+            self.old_allocated_rust,
+            arrow_pyarrow_integration_testing.total_allocated_bytes(),
+        )
 
         # No leak of C++ memory
         self.assertEqual(self.old_allocated_cpp, pyarrow.total_allocated_bytes())
@@ -46,6 +51,7 @@ def test_primitive_rust(self):
         """
         Rust -> Python -> Rust
         """
+
         def double(array):
             array = array.to_pylist()
             return pyarrow.array([x * 2 if x is not None else None for x in array])
@@ -102,9 +108,9 @@ def test_time32_python(self):
         """
         Python -> Rust -> Python
         """
-        a = pyarrow.array([None, 1, 2], pyarrow.time32('s'))
+        a = pyarrow.array([None, 1, 2], pyarrow.time32("s"))
         b = arrow_pyarrow_integration_testing.concatenate(a)
-        expected = pyarrow.array([None, 1, 2] + [None, 1, 2], pyarrow.time32('s'))
+        expected = pyarrow.array([None, 1, 2] + [None, 1, 2], pyarrow.time32("s"))
         self.assertEqual(b, expected)
 
     def test_list_array(self):
@@ -112,7 +118,9 @@ def test_list_array(self):
         Python -> Rust -> Python
         """
         for _ in range(2):
-            a = pyarrow.array([[], None, [1, 2], [4, 5, 6]], pyarrow.list_(pyarrow.int64()))
+            a = pyarrow.array(
+                [[], None, [1, 2], [4, 5, 6]], pyarrow.list_(pyarrow.int64())
+            )
             b = arrow_pyarrow_integration_testing.round_trip(a)
 
             b.validate(full=True)
@@ -124,18 +132,36 @@ def test_struct_array(self):
         Python -> Rust -> Python
         """
         fields = [
-            ('f1', pyarrow.int32()),
-            ('f2', pyarrow.string()),
+            ("f1", pyarrow.int32()),
+            ("f2", pyarrow.string()),
         ]
-        a = pyarrow.array([
-            {"f1": 1, "f2": "a"},
-            None,
-            {"f1": 3, "f2": None},
-            {"f1": None, "f2": "d"},
-            {"f1": None, "f2": None},
-        ], pyarrow.struct(fields))
+        a = pyarrow.array(
+            [
+                {"f1": 1, "f2": "a"},
+                None,
+                {"f1": 3, "f2": None},
+                {"f1": None, "f2": "d"},
+                {"f1": None, "f2": None},
+            ],
+            pyarrow.struct(fields),
+        )
         b = arrow_pyarrow_integration_testing.round_trip(a)
 
         b.validate(full=True)
         assert a.to_pylist() == b.to_pylist()
         assert a.type == b.type
+
+    def test_list_list_array(self):
+        """
+        Python -> Rust -> Python
+        """
+        for _ in range(2):
+            a = pyarrow.array(
+                [[None], None, [[1], [2]], [[4, 5], [6]]],
+                pyarrow.list_(pyarrow.list_(pyarrow.int64())),
+            )
+            b = arrow_pyarrow_integration_testing.round_trip(a)
+
+            b.validate(full=True)
+            assert a.to_pylist() == b.to_pylist()
+            assert a.type == b.type
diff --git a/src/ffi/array.rs b/src/ffi/array.rs
index 65f708cf2eb..3a74cc51872 100644
--- a/src/ffi/array.rs
+++ b/src/ffi/array.rs
@@ -168,4 +168,25 @@ mod tests {
 
         test_round_trip(array)
     }
+
+    #[test]
+    fn test_list_list() -> Result<()> {
+        let data = vec![
+            Some(vec![
+                Some(vec![None]),
+                Some(vec![Some(2)]),
+                Some(vec![Some(3)]),
+            ]),
+            None,
+            Some(vec![Some(vec![Some(4), None, Some(6)])]),
+        ];
+
+        let mut array =
+            MutableListArray::<i32, MutableListArray<i32, MutablePrimitiveArray<i32>>>::new();
+        array.try_extend(data)?;
+
+        let array: ListArray<i32> = array.into();
+
+        test_round_trip(array)
+    }
 }
diff --git a/src/ffi/ffi.rs b/src/ffi/ffi.rs
index 725dc42cbec..a6110af54d5 100644
--- a/src/ffi/ffi.rs
+++ b/src/ffi/ffi.rs
@@ -644,8 +644,8 @@ impl<'a> ArrowArrayRef for ArrowArrayChild<'a> {
         self.schema
     }
 
-    fn child(&self, _: usize) -> Result<ArrowArrayChild> {
-        todo!()
+    fn child(&self, index: usize) -> Result<ArrowArrayChild> {
+        create_child(self.array, self.schema, self.parent.clone(), index)
     }
 }