Fixes #3713: query cache result transformer aliases issue

src/NHibernate.Test/Async/CacheTest/QueryCacheFixture.cs

@@ -11,6 +11,7 @@
 using System.Collections;
 using NHibernate.Cfg;
 using NHibernate.DomainModel;
+using NHibernate.Transform;
 using NUnit.Framework;
 using Environment = NHibernate.Cfg.Environment;
 
@@ -101,5 +102,40 @@ public async Task QueryCacheWithScalarReturnAsync()
 				Assert.That(result, Is.EqualTo(200012), "Unexpected cached result");
 			}
 		}
+
+		[Test]
+		public async Task QueryCacheWithAliasToBeanTransformerAsync()
+		{
+			using (var s = OpenSession())
+			{
+				const string query = "select s.id_ as Id from Simple as s";
+				var result1 = await (s
+					.CreateSQLQuery(query)
+					.SetCacheable(true)
+					.SetResultTransformer(Transformers.AliasToBean<SimpleDTO>())
+					.UniqueResultAsync());
+
+				Assert.That(result1, Is.InstanceOf<SimpleDTO>());
+				var dto1 = (SimpleDTO)result1;
+				Assert.That(dto1.Id, Is.EqualTo(1));
+
+				// Run a second time, just to test the query cache
+				var result2 = await (s
+					.CreateSQLQuery(query)
+					.SetCacheable(true)
+					.SetResultTransformer(Transformers.AliasToBean<SimpleDTO>())
+					.UniqueResultAsync());
+
+				Assert.That(result2, Is.InstanceOf<SimpleDTO>());
+				var dto2 = (SimpleDTO)result2;
+				Assert.That(dto2.Id, Is.EqualTo(1));
+			}
+		}
+
+		private class SimpleDTO
+		{
+			public long Id { get; set; }
+			public string Address { get; set; }
+		}
 	}
 }

src/NHibernate.Test/CacheTest/QueryCacheFixture.cs

@@ -1,6 +1,7 @@
 using System.Collections;
 using NHibernate.Cfg;
 using NHibernate.DomainModel;
+using NHibernate.Transform;
 using NUnit.Framework;
 using Environment = NHibernate.Cfg.Environment;
 
@@ -90,5 +91,40 @@ public void QueryCacheWithScalarReturn()
 				Assert.That(result, Is.EqualTo(200012), "Unexpected cached result");
 			}
 		}
+
+		[Test]
+		public void QueryCacheWithAliasToBeanTransformer()
+		{
+			using (var s = OpenSession())
+			{
+				const string query = "select s.id_ as Id from Simple as s";
+				var result1 = s
+					.CreateSQLQuery(query)
+					.SetCacheable(true)
+					.SetResultTransformer(Transformers.AliasToBean<SimpleDTO>())
+					.UniqueResult();
+
+				Assert.That(result1, Is.InstanceOf<SimpleDTO>());
+				var dto1 = (SimpleDTO)result1;
+				Assert.That(dto1.Id, Is.EqualTo(1));
+
+				// Run a second time, just to test the query cache
+				var result2 = s
+					.CreateSQLQuery(query)
+					.SetCacheable(true)
+					.SetResultTransformer(Transformers.AliasToBean<SimpleDTO>())
+					.UniqueResult();
+
+				Assert.That(result2, Is.InstanceOf<SimpleDTO>());
+				var dto2 = (SimpleDTO)result2;
+				Assert.That(dto2.Id, Is.EqualTo(1));
+			}
+		}
+
+		private class SimpleDTO
+		{
+			public long Id { get; set; }
+			public string Address { get; set; }
+		}
 	}
 }

src/NHibernate/Async/Loader/Loader.cs

@@ -1391,6 +1391,7 @@ private async Task<IList> ListUsingQueryCacheAsync(ISessionImplementor session,
 			else
 			{
 				result = queryCacheBuilder.GetResultList(result);
+				ApplyCachedMetadata(key.ResultTransformer);
 			}
 
 			result = TransformCacheableResults(queryParameters, key.ResultTransformer, result);

src/NHibernate/Loader/Custom/CustomLoader.cs

@@ -380,6 +380,14 @@ public override void AutoDiscoverTypes(
 					queryParameters.ResultTransformer, transformerAliases);
 		}
 
+		protected override void ApplyCachedMetadata(CacheableResultTransformer resultTransformer)
+		{
+			if (transformerAliases.Length == 0 && resultTransformer?.AutoDiscoveredAliases?.Length > 0)
+			{
+				transformerAliases = resultTransformer.AutoDiscoveredAliases;
+			}
+		}
+
 		protected override void ResetEffectiveExpectedType(IEnumerable<IParameterSpecification> parameterSpecs, QueryParameters queryParameters)
 		{
 			parameterSpecs.ResetEffectiveExpectedType(queryParameters);

src/NHibernate/Loader/Loader.cs

@@ -1894,13 +1894,18 @@ private IList ListUsingQueryCache(ISessionImplementor session, QueryParameters q
 			else
 			{
 				result = queryCacheBuilder.GetResultList(result);
+				ApplyCachedMetadata(key.ResultTransformer);
 			}
 
 			result = TransformCacheableResults(queryParameters, key.ResultTransformer, result);
 
 			return GetResultList(result, queryParameters.ResultTransformer);
 		}
 
+		protected virtual void ApplyCachedMetadata(CacheableResultTransformer resultTransformer)
+		{
+		}
+
 		public IList TransformCacheableResults(QueryParameters queryParameters, CacheableResultTransformer transformer, IList result)
 		{
 			var resolvedTransformer = ResolveResultTransformer(queryParameters.ResultTransformer);