From a8052d69368680106bbd2eb540bbf49ec86ac7be Mon Sep 17 00:00:00 2001
From: Kostas <ghost0002001@hotmail.com>
Date: Mon, 8 Jan 2024 15:17:27 +0200
Subject: [PATCH] Fix for #375 - IEnumerable<int?> property serialization.

Signed-off-by: Kostas <ghost0002001@hotmail.com>
---
 CHANGELOG.md                                  |  7 ++-
 .../Mapping/Visitor/PropertyWalker.cs         |  8 +++
 tests/Tests.Reproduce/PropertyWalkerTests .cs | 54 +++++++++++++++++++
 3 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 tests/Tests.Reproduce/PropertyWalkerTests .cs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6fa32748ac..eda57329d1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,11 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Removed
 - Removed the `Features` API which is not supported by OpenSearch from the low-level client ([#331](https://github.com/opensearch-project/opensearch-net/pull/331))
 
+
+### Fixed
+- Fixed `IEnumerable<int?>` property serialization. ([#380](https://github.com/opensearch-project/opensearch-net/pull/375))
+
+
 ### Dependencies
 - Bumps `Microsoft.CodeAnalysis.CSharp` from 4.2.0 to 4.6.0
 - Bumps `NSwag.Core.Yaml` from 13.19.0 to 13.20.0
@@ -118,4 +123,4 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 [Unreleased]: https://github.com/opensearch-project/opensearch-net/compare/v1.5.0...main
 [1.5.0]: https://github.com/opensearch-project/opensearch-net/compare/v1.4.0...v1.5.0
 [1.4.0]: https://github.com/opensearch-project/opensearch-net/compare/v1.3.0...v1.4.0
-[1.3.0]: https://github.com/opensearch-project/opensearch-net/compare/v1.2.0...v1.3.0
\ No newline at end of file
+[1.3.0]: https://github.com/opensearch-project/opensearch-net/compare/v1.2.0...v1.3.0
diff --git a/src/OpenSearch.Client/Mapping/Visitor/PropertyWalker.cs b/src/OpenSearch.Client/Mapping/Visitor/PropertyWalker.cs
index c95dcb9812..6280a36ef0 100644
--- a/src/OpenSearch.Client/Mapping/Visitor/PropertyWalker.cs
+++ b/src/OpenSearch.Client/Mapping/Visitor/PropertyWalker.cs
@@ -227,5 +227,13 @@ bool ShouldUnwrapType(Type ty)
 						);
 			}
 		}
+
+		private static bool ShouldUnwrapType(Type ty) =>
+					ty.IsGenericType &&
+					ty.GetGenericArguments().Length == 1
+					&& (
+						ty.GetInterfaces().HasAny(t => t == typeof(IEnumerable)) ||
+						Nullable.GetUnderlyingType(ty) != null
+					);
 	}
 }
diff --git a/tests/Tests.Reproduce/PropertyWalkerTests .cs b/tests/Tests.Reproduce/PropertyWalkerTests .cs
new file mode 100644
index 0000000000..dd7a0d3ad1
--- /dev/null
+++ b/tests/Tests.Reproduce/PropertyWalkerTests .cs	
@@ -0,0 +1,54 @@
+using System.Collections.Generic;
+using System.Linq;
+using FluentAssertions;
+using OpenSearch.Client;
+using OpenSearch.OpenSearch.Xunit.XunitPlumbing;
+
+namespace Tests.Reproduce
+{
+	public class PropertyWalkerTests
+	{
+		[U]
+		public void IEnumerableOfNullablesGetsMappedCorrectly()
+		{
+			var result = TestPropertyType<IEnumerable<int?>>();
+			result.Should().Be("integer");
+		}
+
+		[U]
+		public void IListOfNullablesGetsMappedCorrectly()
+		{
+			var result = TestPropertyType<IList<int?>>();
+			result.Should().Be("integer");
+		}
+
+		[U]
+		public void IEnumerableOfValueTypesGetsMappedCorrectly()
+		{
+			var result = TestPropertyType<IEnumerable<int>>();
+			result.Should().Be("integer");
+		}
+
+		[U]
+		public void IListOfValueTypesGetsMappedCorrectly()
+		{
+			var result = TestPropertyType<IList<int>>();
+			result.Should().Be("integer");
+		}
+
+		private static string TestPropertyType<T>()
+		{
+			var walker = new PropertyWalker(typeof(Test<T>), null, 0);
+			var properties = walker.GetProperties();
+			var result = properties.SingleOrDefault();
+			return result.Value?.Type;
+		}
+
+
+		private class Test<T>
+		{
+			public T Values { get; set; }
+		}
+
+	}
+}