Fix Get failing with a null exception

Author: fredericDelaporte

src/NHibernate.Test/Async/NHSpecificTest/GH1920/Fixture.cs

@@ -0,0 +1,62 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by AsyncGenerator.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+
+using System;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH1920
+{
+	using System.Threading.Tasks;
+	using System.Threading;
+	[TestFixture]
+	public class FixtureAsync : BugTestCase
+	{
+		private Guid entityId;
+		private Guid someOtherEntityId;
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				entityId = (Guid) session.Save(new EntityWithBatchSize { Name = "some name" });
+				someOtherEntityId = (Guid) session.Save(new EntityWithBatchSize());
+
+				transaction.Commit();
+			}
+		}
+
+		[TestCase(true)]
+		[TestCase(false)]
+		public async Task CanLoadEntityAsync(bool loadProxyOfOtherEntity, CancellationToken cancellationToken = default(CancellationToken))
+		{
+			using (var session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				if (loadProxyOfOtherEntity)
+					await (session.LoadAsync<EntityWithBatchSize>(someOtherEntityId, cancellationToken));
+
+				var result = await (session.GetAsync<EntityWithBatchSize>(entityId, cancellationToken));
+
+				Assert.That(result.Name, Is.Not.Null);
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var transaction = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from EntityWithBatchSize").ExecuteUpdate();
+				transaction.Commit();
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH1920/Fixture.cs

@@ -8,13 +8,13 @@ public class Fixture : BugTestCase
 	{
 		private Guid entityId;
 		private Guid someOtherEntityId;
-	
+
 		protected override void OnSetUp()
 		{
 			using (var session = OpenSession())
 			using (var transaction = session.BeginTransaction())
 			{
-				entityId = (Guid) session.Save(new EntityWithBatchSize {Name = "some name"});
+				entityId = (Guid) session.Save(new EntityWithBatchSize { Name = "some name" });
 				someOtherEntityId = (Guid) session.Save(new EntityWithBatchSize());
 
 				transaction.Commit();
@@ -28,16 +28,15 @@ public void CanLoadEntity(bool loadProxyOfOtherEntity)
 			using (var session = OpenSession())
 			using (session.BeginTransaction())
 			{
-				if(loadProxyOfOtherEntity)
+				if (loadProxyOfOtherEntity)
 					session.Load<EntityWithBatchSize>(someOtherEntityId);
-				
+
 				var result = session.Get<EntityWithBatchSize>(entityId);
 
 				Assert.That(result.Name, Is.Not.Null);
 			}
 		}
-		
-		
+
 		protected override void OnTearDown()
 		{
 			using (var session = OpenSession())

src/NHibernate/Async/Engine/BatchFetchQueue.cs

@@ -295,7 +295,10 @@ async Task<bool> CheckCacheAndProcessResultAsync()
 					? entityKeys.Count - Math.Min(batchSize, entityKeys.Count)
 					: 0;
 				var toIndex = entityKeys.Count - 1;
-				var indexes = GetSortedKeyIndexes(entityKeys, idIndex.Value, fromIndex, toIndex);
+				// In case of an ISession.Get on an entity not already loaded as an uninitialized proxy,
+				// it will not be found in entities awaiting a load, and idIndex will be null. Providing
+				// -1 then allows to take the entities most recently loaded as uninitialized proxies.
+				var indexes = GetSortedKeyIndexes(entityKeys, idIndex ?? -1, fromIndex, toIndex);
 				if (batchableCache == null)
 				{
 					for (var j = 0; j < entityKeys.Count; j++)

src/NHibernate/Engine/BatchFetchQueue.cs

@@ -455,7 +455,10 @@ bool CheckCacheAndProcessResult()
 					? entityKeys.Count - Math.Min(batchSize, entityKeys.Count)
 					: 0;
 				var toIndex = entityKeys.Count - 1;
-				var indexes = GetSortedKeyIndexes(entityKeys, idIndex.Value, fromIndex, toIndex);
+				// In case of an ISession.Get on an entity not already loaded as an uninitialized proxy,
+				// it will not be found in entities awaiting a load, and idIndex will be null. Providing
+				// -1 then allows to take the entities most recently loaded as uninitialized proxies.
+				var indexes = GetSortedKeyIndexes(entityKeys, idIndex ?? -1, fromIndex, toIndex);
 				if (batchableCache == null)
 				{
 					for (var j = 0; j < entityKeys.Count; j++)
@@ -612,11 +615,11 @@ private bool[] AreCached(List<KeyValuePair<KeyValuePair<CollectionEntry, IPersis
 		}
 
 		/// <summary>
-		/// Sorts the given keys by thier indexes, where the keys that are after the demanded key will be located
+		/// Sorts the given keys by their indexes, where the keys that are after the demanded key will be located
 		/// at the start and the remaining indexes at the end of the returned array.
 		/// </summary>
 		/// <typeparam name="T">The type of the key</typeparam>
-		/// <param name="keys">The list of pairs of keys and thier indexes.</param>
+		/// <param name="keys">The list of pairs of keys and their indexes.</param>
 		/// <param name="keyIndex">The index of the demanded key</param>
 		/// <param name="fromIndex">The index where the sorting will begin.</param>
 		/// <param name="toIndex">The index where the sorting will end.</param>