From f80f256f00d3e850ebbc7c754326b5336f4d2660 Mon Sep 17 00:00:00 2001
From: sytherax <swooruptrader@gmail.com>
Date: Tue, 10 Feb 2026 21:51:34 +1100
Subject: [PATCH] feat: add serialization test for list element name and
 metadata support

---
 arrow_convert/tests/test_schema.rs        | 34 ++++++++++++++++++++++-
 arrow_convert_derive/src/derive_struct.rs | 27 ++++++++++++++++++
 2 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/arrow_convert/tests/test_schema.rs b/arrow_convert/tests/test_schema.rs
index aebfcea..bffb9bb 100644
--- a/arrow_convert/tests/test_schema.rs
+++ b/arrow_convert/tests/test_schema.rs
@@ -3,7 +3,8 @@ use std::sync::Arc;
 use arrow::datatypes::*;
 use arrow_convert::{
     field::{with_list_element_metadata, with_list_element_name, DEFAULT_FIELD_NAME},
-    ArrowField,
+    serialize::TryIntoArrow,
+    ArrowField, ArrowSerialize,
 };
 use pretty_assertions::assert_eq;
 
@@ -447,3 +448,34 @@ fn test_with_list_element_helpers_for_large_and_fixed_size_lists() {
     assert_eq!(fixed_element.name(), "level");
     assert_eq!(fixed_element.metadata().get("kind"), Some(&"depth".to_string()));
 }
+
+#[test]
+fn test_serialize_respects_list_element_name_and_metadata() {
+    #[derive(Debug, ArrowField, ArrowSerialize)]
+    #[allow(dead_code)]
+    #[arrow_field(list_element_metadata(scope = "container"))]
+    struct Root {
+        #[arrow_field(list_element_name = "level", list_element_metadata(PARQUET::field_id = "9"))]
+        bids: Vec<i64>,
+    }
+
+    let rows = vec![Root { bids: vec![1, 2, 3] }];
+    let array: arrow::array::ArrayRef = rows.try_into_arrow().expect("serialization should succeed");
+    let struct_array = array
+        .as_any()
+        .downcast_ref::<arrow::array::StructArray>()
+        .expect("expected StructArray");
+
+    let fields = struct_array.fields();
+    let bids = &fields[0];
+    let DataType::List(element) = bids.data_type() else {
+        panic!("expected list datatype");
+    };
+
+    assert_eq!(element.name(), "level");
+    assert_eq!(element.metadata().get("scope"), Some(&"container".to_string()));
+    assert_eq!(
+        element.metadata().get("PARQUET:field_id"),
+        Some(&"9".to_string())
+    );
+}
diff --git a/arrow_convert_derive/src/derive_struct.rs b/arrow_convert_derive/src/derive_struct.rs
index f99742a..c97fa27 100644
--- a/arrow_convert_derive/src/derive_struct.rs
+++ b/arrow_convert_derive/src/derive_struct.rs
@@ -295,6 +295,31 @@ pub fn expand_serialize(input: DeriveStruct) -> TokenStream {
                 }
                 Ok(())
             }
+
+            fn align_struct_values(
+                values: Vec<arrow::array::ArrayRef>,
+                fields: &arrow::datatypes::Fields,
+            ) -> Vec<arrow::array::ArrayRef> {
+                values
+                    .into_iter()
+                    .zip(fields.iter())
+                    .map(|(value, field)| {
+                        if value.data_type() == field.data_type() {
+                            value
+                        } else {
+                            arrow::compute::cast(value.as_ref(), field.data_type()).unwrap_or_else(|e| {
+                                panic!(
+                                    "failed to cast field '{}' from {:?} to {:?}: {}",
+                                    field.name(),
+                                    value.data_type(),
+                                    field.data_type(),
+                                    e
+                                )
+                            })
+                        }
+                    })
+                    .collect()
+            }
         }
     };
 
@@ -346,6 +371,7 @@ pub fn expand_serialize(input: DeriveStruct) -> TokenStream {
                   .clone() else {
                     panic!("datatype is not struct")
                   };
+                let values = #mutable_array_name::align_struct_values(values, &fields);
 
                 std::sync::Arc::new(arrow::array::StructArray::new(
                     fields,
@@ -364,6 +390,7 @@ pub fn expand_serialize(input: DeriveStruct) -> TokenStream {
                   .clone() else {
                     panic!("datatype is not struct")
                   };
+                let values = #mutable_array_name::align_struct_values(values, &fields);
 
                 std::sync::Arc::new(arrow::array::StructArray::new(
                     fields,