Fix for appending lists with null

* Add failing test

* Make test pass

* Alternative test implementation. Reduce data size from 2000 rows to 10 rows.

Author: brendonparker

DuckDB.NET.Data/Internal/Writer/ListVectorDataWriter.cs

@@ -33,33 +33,54 @@ internal override bool AppendCollection(ICollection value, int rowIndex)
         _ = value switch
         {
             IEnumerable<bool> items => WriteItems(items),
+            IEnumerable<bool?> items => WriteItems(items),
 
             IEnumerable<sbyte> items => WriteItems(items),
+            IEnumerable<sbyte?> items => WriteItems(items),
             IEnumerable<short> items => WriteItems(items),
+            IEnumerable<short?> items => WriteItems(items),
             IEnumerable<int> items => WriteItems(items),
+            IEnumerable<int?> items => WriteItems(items),
             IEnumerable<long> items => WriteItems(items),
+            IEnumerable<long?> items => WriteItems(items),
             IEnumerable<byte> items => WriteItems(items),
+            IEnumerable<byte?> items => WriteItems(items),
             IEnumerable<ushort> items => WriteItems(items),
+            IEnumerable<ushort?> items => WriteItems(items),
             IEnumerable<uint> items => WriteItems(items),
+            IEnumerable<uint?> items => WriteItems(items),
             IEnumerable<ulong> items => WriteItems(items),
+            IEnumerable<ulong?> items => WriteItems(items),
 
             IEnumerable<float> items => WriteItems(items),
+            IEnumerable<float?> items => WriteItems(items),
             IEnumerable<double> items => WriteItems(items),
+            IEnumerable<double?> items => WriteItems(items),
 
             IEnumerable<decimal> items => WriteItems(items),
+            IEnumerable<decimal?> items => WriteItems(items),
             IEnumerable<BigInteger> items => WriteItems(items),
+            IEnumerable<BigInteger?> items => WriteItems(items),
 
             IEnumerable<string> items => WriteItems(items),
             IEnumerable<Guid> items => WriteItems(items),
+            IEnumerable<Guid?> items => WriteItems(items),
             IEnumerable<DateTime> items => WriteItems(items),
+            IEnumerable<DateTime?> items => WriteItems(items),
             IEnumerable<TimeSpan> items => WriteItems(items),
+            IEnumerable<TimeSpan?> items => WriteItems(items),
             IEnumerable<DuckDBDateOnly> items => WriteItems(items),
+            IEnumerable<DuckDBDateOnly?> items => WriteItems(items),
             IEnumerable<DuckDBTimeOnly> items => WriteItems(items),
+            IEnumerable<DuckDBTimeOnly?> items => WriteItems(items),
 #if NET6_0_OR_GREATER
             IEnumerable<DateOnly> items => WriteItems(items),
+            IEnumerable<DateOnly?> items => WriteItems(items),
             IEnumerable<TimeOnly> items => WriteItems(items),
+            IEnumerable<TimeOnly?> items => WriteItems(items),
 #endif
             IEnumerable<DateTimeOffset> items => WriteItems(items),
+            IEnumerable<DateTimeOffset?> items => WriteItems(items),
 
             _ => WriteItems<object>((IEnumerable<object>)value)
         };

DuckDB.NET.Test/DuckDBManagedAppenderListTests.cs

@@ -129,9 +129,15 @@ public void ArrayValuesInt()
         ListValuesInternal("Integer", faker => faker.Random.Int(), 5);
     }
 
+    [Fact]
+    public void ListValuesNullableDouble()
+    {
+        ListValuesInternal("Double", faker => faker.Random.Double().OrNull(faker));
+    }
+
     private void ListValuesInternal<T>(string typeName, Func<Faker, T> generator, int? length = null)
     {
-        var rows = 2000;
+        var rows = 10;
         var table = $"managedAppenderLists";
 
         var columnLength = length.HasValue ? length.Value.ToString() : "";