Fix NRE in linq processing of custom components (#2941)

fix #2937

Co-authored-by: Duncan M <duncan@pleasantsolutions.com>
Co-authored-by: Roman Artiukhin <bahusdrive@gmail.com>

Author: 3 people

src/NHibernate.Test/Async/Hql/EntityJoinHqlTest.cs

@@ -346,9 +346,9 @@ public async Task NullableEntityProjectionAsync()
 				var withNullManyToOneList = await (session.Query<NullableOwner>().Where(x => x.ManyToOne == null).ToListAsync());
 				var withNullManyToOneJoinedList =
 					await ((from x in session.Query<NullableOwner>()
-							from x2 in session.Query<NullableOwner>()
-							where x == x2 && x.ManyToOne == null && x.OneToOne.Name == null
-							select x2).ToListAsync());
+					from x2 in session.Query<NullableOwner>()
+					where x == x2 && x.ManyToOne == null && x.OneToOne.Name == null
+					select x2).ToListAsync());
 				Assert.That(fullList.Count, Is.EqualTo(2));
 				Assert.That(withValidManyToOneList.Count, Is.EqualTo(0));
 				Assert.That(withValidManyToOneList2.Count, Is.EqualTo(0));

src/NHibernate.Test/Linq/TryGetMappedTests.cs

@@ -272,6 +272,19 @@ public void NestedComponentPropertyCastTest()
 				o => o?.Name == "component[OtherProperty1]");
 		}
 
+		[Test(Description = "GH-2937")]
+		public void CompositeUserTypePropertyTest()
+		{
+			var query = session.Query<Glarch>().Select(o => o.Multiple.count);
+			AssertSupported(
+				query,
+				typeof(Glarch).FullName,
+				"Multiple.count",
+				o => o is Int32Type,
+				o => o?.Name == typeof(MultiplicityType).FullName,
+				null);
+		}
+
 		[Test]
 		public void ManyToOneTest()
 		{
@@ -723,9 +736,10 @@ private void AssertSupported(
 			string expectedEntityName,
 			string expectedMemberPath,
 			Predicate<IType> expectedMemberType,
-			Predicate<IAbstractComponentType> expectedComponentType = null)
+			Predicate<IAbstractComponentType> expectedComponentType = null,
+			bool? nullability = true)
 		{
-			AssertResult(query, true, true, expectedEntityName, expectedMemberPath, expectedMemberType, expectedComponentType);
+			AssertResult(query, true, true, expectedEntityName, expectedMemberPath, expectedMemberType, expectedComponentType, nullability);
 		}
 
 		private void AssertSupported(
@@ -768,7 +782,7 @@ private void AssertResult(
 			string expectedMemberPath,
 			Predicate<IType> expectedMemberType,
 			Predicate<IAbstractComponentType> expectedComponentType = null,
-			bool nullability = true)
+			bool? nullability = true)
 		{
 			expectedComponentType = expectedComponentType ?? (o => o == null);
 
@@ -809,8 +823,12 @@ private void AssertResult(
 
 			if (found)
 			{
-				Assert.That(_tryGetMappedNullability(Sfi, queryModel.SelectClause.Selector, out var isNullable), Is.True, "Expression should be supported");
-				Assert.That(nullability, Is.EqualTo(isNullable), "Nullability is not correct");
+				Assert.That(
+					_tryGetMappedNullability(Sfi, queryModel.SelectClause.Selector, out var isNullable),
+					Is.EqualTo(nullability.HasValue),
+					$"Expression should be {(nullability.HasValue ? "supported" : "unsupported")}");
+				if (nullability.HasValue)
+					Assert.That(nullability, Is.EqualTo(isNullable), "Nullability is not correct");
 			}
 		}
 	}

src/NHibernate/Util/ExpressionsHelper.cs

@@ -160,10 +160,17 @@ internal static bool TryGetMappedNullability(
 			int index;
 			if (componentType != null)
 			{
+				var propertyNullability = componentType.PropertyNullability;
+				if (propertyNullability == null)
+				{
+					nullable = false;
+					return false;
+				}
+
 				index = Array.IndexOf(
 					componentType.PropertyNames,
 					memberPath.Substring(memberPath.LastIndexOf('.') + 1));
-				nullable = componentType.PropertyNullability[index];
+				nullable = propertyNullability[index];
 				return true;
 			}