Fix optional_object_attributes to be Optional in ListObjectsV2Input

Co-authored-by: Nugine <[email protected]>

Author: Copilot

codegen/src/v1/aws_conv.rs

@@ -103,9 +103,6 @@ pub fn codegen(ops: &Operations, rust_types: &RustTypes) {
                     let field_ty = &rust_types[field.type_.as_str()];
 
                     let needs_unwrap = 'unwrap: {
-                        if field.type_ == "OptionalObjectAttributesList" {
-                            break 'unwrap true;
-                        }
                         if is_op_input(&ty.name, ops) && field.option_type.not() && field.is_required {
                             break 'unwrap true;
                         }

codegen/src/v1/dto.rs

@@ -152,6 +152,10 @@ pub fn collect_rust_types(model: &smithy::Model, ops: &Operations) -> RustTypes
                         }
                         if is_op_input && is_required.not() {
                             if field_type.ends_with("List") {
+                                // Exception: OptionalObjectAttributesList should be optional
+                                if field_type == "OptionalObjectAttributesList" {
+                                    break 'optional true;
+                                }
                                 break 'optional false;
                             }
                             break 'optional true;

codegen/src/v1/ops.rs

@@ -425,13 +425,21 @@ fn codegen_op_http_de(op: &Operation, rust_types: &RustTypes) {
                             let field_type = &rust_types[&field.type_];
 
                             if let rust::Type::List(_) = field_type {
-                                assert!(field.option_type.not());
-                                g!(
-                                    "let {}: {} = http::parse_list_header(req, &{header}, {})?;",
-                                    field.name,
-                                    field.type_,
-                                    field.is_required
-                                );
+                                if field.option_type {
+                                    // Special case for optional list headers (e.g., OptionalObjectAttributesList)
+                                    g!(
+                                        "let {}: Option<{}> = http::parse_opt_list_header(req, &{header})?;",
+                                        field.name,
+                                        field.type_
+                                    );
+                                } else {
+                                    g!(
+                                        "let {}: {} = http::parse_list_header(req, &{header}, {})?;",
+                                        field.name,
+                                        field.type_,
+                                        field.is_required
+                                    );
+                                }
                             } else if let rust::Type::Timestamp(ts_ty) = field_type {
                                 assert!(field.option_type);
                                 let fmt = ts_ty.format.as_deref().unwrap_or("HttpDate");