Fix System.InvalidCastException when merge collection with LazyProperty

src/NHibernate.Test/Async/LazyProperty/LazyPropertyFixture.cs

@@ -9,6 +9,7 @@
 
 
 using System.Collections;
+using System.Collections.Generic;
 using System.Linq;
 using NHibernate.Cfg;
 using NHibernate.Intercept;
@@ -81,6 +82,7 @@ protected override void OnTearDown()
 			using (var s = OpenSession())
 			using (var tx = s.BeginTransaction())
 			{
+				s.CreateQuery("delete from Word").ExecuteUpdate();
 				s.CreateQuery("delete from Book").ExecuteUpdate();
 				tx.Commit();
 			}
@@ -345,5 +347,56 @@ public async Task CacheShouldNotContainLazyPropertiesAsync()
 			Assert.That(NHibernateUtil.IsPropertyInitialized(book, "ALotOfText"), Is.False);
 			Assert.That(NHibernateUtil.IsPropertyInitialized(book, "Image"), Is.False);
 		}
+
+		[Test]
+		public async Task CanMergeTransientWithLazyPropertyInCollectionAsync()
+		{
+			Book book;
+
+			using (var s = OpenSession())
+			using (var tx = s.BeginTransaction())
+			{
+				book = new Book
+				{
+					Name = "some name two",
+					Id = 3,
+					ALotOfText = "a lot of text two..."
+				};
+				// This should insert a new entity.
+				await (s.MergeAsync(book));
+				await (tx.CommitAsync());
+			}
+
+			using (var s = OpenSession())
+			{
+				book = await (s.GetAsync<Book>(3));
+				Assert.That(book, Is.Not.Null);
+				Assert.That(book.Name, Is.EqualTo("some name two"));
+				Assert.That(book.ALotOfText, Is.EqualTo("a lot of text two..."));
+
+			}
+			using (var s = OpenSession())
+			using (var tx = s.BeginTransaction())
+			{
+				book.Words = new List<Word>();
+				var word = new Word
+				{
+					Id = 2,
+					Parent = book,
+					Content = new byte[1] {0}
+				};
+
+				book.Words.Add(word);
+				await (s.MergeAsync(book));
+				await (tx.CommitAsync());
+			}
+
+			using (var s = OpenSession())
+			{
+				book = await (s.GetAsync<Book>(3));
+				Assert.That(book.Words.Any(), Is.True);
+				Assert.That(book.Words.First().Content, Is.EqualTo(new byte[1] { 0 }));
+			}
+		}
 	}
 }

src/NHibernate.Test/LazyProperty/Book.cs

@@ -1,4 +1,6 @@
-namespace NHibernate.Test.LazyProperty
+using System.Collections.Generic;
+
+namespace NHibernate.Test.LazyProperty
 {
 	public class Book
 	{
@@ -16,5 +18,7 @@ public virtual string ALotOfText
 		public virtual byte[] Image { get; set; }
 
 		public virtual string FieldInterceptor { get; set; }
+
+		public virtual IList<Word> Words { get; set; }
 	}
 }

src/NHibernate.Test/LazyProperty/LazyPropertyFixture.cs

@@ -1,4 +1,5 @@
 using System.Collections;
+using System.Collections.Generic;
 using System.Linq;
 using NHibernate.Cfg;
 using NHibernate.Intercept;
@@ -68,6 +69,7 @@ protected override void OnTearDown()
 			using (var s = OpenSession())
 			using (var tx = s.BeginTransaction())
 			{
+				s.CreateQuery("delete from Word").ExecuteUpdate();
 				s.CreateQuery("delete from Book").ExecuteUpdate();
 				tx.Commit();
 			}
@@ -338,5 +340,56 @@ public void CacheShouldNotContainLazyProperties()
 			Assert.That(NHibernateUtil.IsPropertyInitialized(book, "ALotOfText"), Is.False);
 			Assert.That(NHibernateUtil.IsPropertyInitialized(book, "Image"), Is.False);
 		}
+
+		[Test]
+		public void CanMergeTransientWithLazyPropertyInCollection()
+		{
+			Book book;
+
+			using (var s = OpenSession())
+			using (var tx = s.BeginTransaction())
+			{
+				book = new Book
+				{
+					Name = "some name two",
+					Id = 3,
+					ALotOfText = "a lot of text two..."
+				};
+				// This should insert a new entity.
+				s.Merge(book);
+				tx.Commit();
+			}
+
+			using (var s = OpenSession())
+			{
+				book = s.Get<Book>(3);
+				Assert.That(book, Is.Not.Null);
+				Assert.That(book.Name, Is.EqualTo("some name two"));
+				Assert.That(book.ALotOfText, Is.EqualTo("a lot of text two..."));
+
+			}
+			using (var s = OpenSession())
+			using (var tx = s.BeginTransaction())
+			{
+				book.Words = new List<Word>();
+				var word = new Word
+				{
+					Id = 2,
+					Parent = book,
+					Content = new byte[1] {0}
+				};
+
+				book.Words.Add(word);
+				s.Merge(book);
+				tx.Commit();
+			}
+
+			using (var s = OpenSession())
+			{
+				book = s.Get<Book>(3);
+				Assert.That(book.Words.Any(), Is.True);
+				Assert.That(book.Words.First().Content, Is.EqualTo(new byte[1] { 0 }));
+			}
+		}
 	}
 }

src/NHibernate.Test/LazyProperty/Mappings.hbm.xml

@@ -12,6 +12,18 @@
 		<property name="ALotOfText" lazy="true" />
 		<property name="Image" lazy="true" />
 		<property name="FieldInterceptor" />
+    <bag name="Words" inverse="true" generic="true" cascade="all-delete-orphan" lazy="true" >
+      <key column="ParentId" />
+      <one-to-many class="Word" />
+    </bag>
 	</class>
 
+  <class name="Word">
+    <id name="Id" column="Id">
+      <generator class="assigned" />
+    </id>
+    <property name="Content" lazy="true" />
+    <many-to-one name="Parent" class="Book" column="ParentId" />
+  </class>
+
 </hibernate-mapping>

src/NHibernate.Test/LazyProperty/Word.cs

@@ -0,0 +1,9 @@
+namespace NHibernate.Test.LazyProperty
+{
+	public class Word
+	{
+		public virtual int Id { get; set; }
+		public virtual byte[] Content { get; set; }
+		public virtual Book Parent { get; set; }
+	}
+}

src/NHibernate/Async/Type/TypeHelper.cs

@@ -169,6 +169,25 @@ public static async Task<object[]> ReplaceAsync(object[] original, object[] targ
 				{
 					copied[i] = target[i];
 				}
+				else if (target[i] == LazyPropertyInitializer.UnfetchedProperty)
+				{
+					// Should be no need to check for target[i] == PropertyAccessStrategyBackRefImpl.UNKNOWN
+					// because PropertyAccessStrategyBackRefImpl.get( object ) returns
+					// PropertyAccessStrategyBackRefImpl.UNKNOWN, so target[i] == original[i].
+					//
+					// We know from above that original[i] != LazyPropertyInitializer.UNFETCHED_PROPERTY &&
+					// original[i] != PropertyAccessStrategyBackRefImpl.UNKNOWN;
+					// This is a case where the entity being merged has a lazy property
+					// that has been initialized. Copy the initialized value from original.
+					if (types[i].IsMutable)
+					{
+						copied[i] = types[i].DeepCopy(original[i], session.Factory);
+					}
+					else
+					{
+						copied[i] = original[i];
+					}
+				}
 				else
 					copied[i] = await (types[i].ReplaceAsync(original[i], target[i], session, owner, copyCache, foreignKeyDirection, cancellationToken)).ConfigureAwait(false);
 			}
@@ -343,4 +362,4 @@ public static async Task<int[]> FindModifiedAsync(StandardProperty[] properties,
 			}
 		}
 	}
-}
+}

src/NHibernate/Type/TypeHelper.cs

@@ -175,6 +175,25 @@ public static object[] Replace(object[] original, object[] target, IType[] types
 				{
 					copied[i] = target[i];
 				}
+				else if (target[i] == LazyPropertyInitializer.UnfetchedProperty)
+				{
+					// Should be no need to check for target[i] == PropertyAccessStrategyBackRefImpl.UNKNOWN
+					// because PropertyAccessStrategyBackRefImpl.get( object ) returns
+					// PropertyAccessStrategyBackRefImpl.UNKNOWN, so target[i] == original[i].
+					//
+					// We know from above that original[i] != LazyPropertyInitializer.UNFETCHED_PROPERTY &&
+					// original[i] != PropertyAccessStrategyBackRefImpl.UNKNOWN;
+					// This is a case where the entity being merged has a lazy property
+					// that has been initialized. Copy the initialized value from original.
+					if (types[i].IsMutable)
+					{
+						copied[i] = types[i].DeepCopy(original[i], session.Factory);
+					}
+					else
+					{
+						copied[i] = original[i];
+					}
+				}
 				else
 					copied[i] = types[i].Replace(original[i], target[i], session, owner, copyCache, foreignKeyDirection);
 			}
@@ -342,4 +361,4 @@ public static int[] FindModified(StandardProperty[] properties,
 			}
 		}
 	}
-}
+}