From 9968ea0bbf8408c4a99aafa10f56748b80854b2f Mon Sep 17 00:00:00 2001
From: Cedric Conday <neumann.alpha@gmail.com>
Date: Tue, 30 Jun 2026 03:02:35 +0000
Subject: [PATCH] Deserialize a null list field as None instead of raising
 (#131)

The Xero API can return null for an array field (e.g.
reject_leave_application responds with "LeaveApplications": None).
deserialize_list then tried to iterate over None and raised
TypeError: 'NoneType' object is not iterable.

Return None when data is None, mirroring how deserialize_model already
handles a null payload.

Closes #131.
---
 tests/test_api_client/test_deserializer.py | 7 +++++++
 xero_python/api_client/deserializer.py     | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/tests/test_api_client/test_deserializer.py b/tests/test_api_client/test_deserializer.py
index 9c851a8a..731965bb 100644
--- a/tests/test_api_client/test_deserializer.py
+++ b/tests/test_api_client/test_deserializer.py
@@ -111,6 +111,13 @@ def test_deserialize_list_key_error():
         deserialize_list(data_type, data, model_finder)
 
 
+def test_deserialize_list_none():
+    # regression for #131: the Xero API can return null for a list field
+    # (e.g. "LeaveApplications": None); deserializing must not raise.
+    result = deserialize_list("list[number]", None, model_finder=None)
+    assert result is None
+
+
 # deserialize_int tests
 @pytest.mark.parametrize("data,expected", [(n, int(n)) for n in ("1", "-1", 2)])
 def test_deserialize_int(data, expected):
diff --git a/xero_python/api_client/deserializer.py b/xero_python/api_client/deserializer.py
index b64e9820..01af91d3 100644
--- a/xero_python/api_client/deserializer.py
+++ b/xero_python/api_client/deserializer.py
@@ -70,6 +70,8 @@ def deserialize_list(data_type, data, model_finder):
     :return: deserialized list
 
     """
+    if data is None:
+        return None
     try:
         sub_data_type = LIST_DATA_TYPE.match(data_type).group(1)
     except AttributeError: