perf: reuse no data array and empty task

TUnit.Core/Attributes/TestData/NoDataSource.cs

@@ -2,14 +2,15 @@
 
 internal class NoDataSource : IDataSourceAttribute
 {
+    private static readonly Task<object?[]?> _emptyRowTask = Task.FromResult<object?[]?>([]);
     public static readonly NoDataSource Instance = new();
 
     /// <inheritdoc />
     public bool SkipIfEmpty { get; set; }
 
     public async IAsyncEnumerable<Func<Task<object?[]?>>> GetDataRowsAsync(DataGeneratorMetadata dataGeneratorMetadata)
     {
-        yield return () => Task.FromResult<object?[]?>([]);
+        yield return static () => _emptyRowTask;
         await default(ValueTask);
     }
 }

TUnit.Engine/Building/TestBuilder.cs

@@ -812,11 +812,13 @@ private static Type[] TryInferClassGenericsFromDataSources(TestMetadata metadata
         return resolvedTypes;
     }
 
+    private static readonly IDataSourceAttribute[] _dataSourceArray = [NoDataSource.Instance];
+
     private async Task<IDataSourceAttribute[]> GetDataSourcesAsync(IDataSourceAttribute[] dataSources)
     {
         if (dataSources.Length == 0)
         {
-            return [NoDataSource.Instance];
+            return _dataSourceArray;
         }
 
         // Inject properties into data sources during discovery (IAsyncInitializer deferred to execution)