Fetching a lazy loaded component regression

[nfplee]

I have identified a regression introduced in version 5.3.0. It happens when trying to fetch a lazy loaded component which has a read-only property and is mapped as an interface.

It's a little querky to explain but I've tried to produce a minimal sample to show you the issue.

Please see the attached application (making sure to set the connection string). The database must have the following structure:

CREATE TABLE [dbo].[ContentItems](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[Name] [nvarchar](100) NOT NULL,
	[PageTitle] [nvarchar](1024) NULL
)

INSERT INTO [dbo].[ContentItems] ([Name]) VALUES ('Test')

SQL above edited after realising that the table must have data to reproduce.

  var contentItems = await session.Query<ContentItem>()
      .Fetch(i => i.Head)
      .ToListAsync();

Exception:

NHibernate.Exceptions.GenericADOException
  Message=could not execute query
[ select contentite0_.Id as id1_0_, contentite0_.Name as name2_0_, contentite0_.PageTitle as pagetitle3_0_ from ContentItems contentite0_ ]
  StackTrace:
   at NHibernate.Loader.Loader.<DoListAsync>d__38.MoveNext()
...

  This exception was originally thrown at this call stack:
  System.IndexOutOfRangeException: formula0_
   at System.Data.ProviderBase.BasicFieldNameLookup.GetOrdinal(String fieldName)
   at System.Data.SqlClient.SqlDataReader.GetOrdinal(String name)
   at NHibernate.Driver.NHybridDataReader.GetOrdinal(String name)
   at NHibernate.Type.NullableType.NullSafeGet(DbDataReader rs, String name, ISessionImplementor session)
   at NHibernate.Type.NullableType.NullSafeGet(DbDataReader rs, String[] names, ISessionImplementor session, Object owner)
   at NHibernate.Type.NullableType.NullSafeGetAsync(DbDataReader rs, String[] names, ISessionImplementor session, Object owner, CancellationToken cancellationToken)
--- End of stack trace from previous location ---
   at NHibernate.Type.ComponentType.HydrateAsync(DbDataReader rs, String[] names, ISessionImplementor session, Object owner, CancellationToken cancellationToken)
   at NHibernate.Persister.Entity.AbstractEntityPersister.HydrateAsync(DbDataReader rs, Object id, Object obj, String[][] suffixedPropertyColumns, ISet`1 fetchedLazyProperties, Boolean allProperties, Int32[] indexes, ISessionImplementor session, CancellationToken cancellationToken)
   at NHibernate.Loader.Loader.LoadFromResultSetAsync(DbDataReader rs, Int32 i, Object obj, ILoadable persister, EntityKey key, LockMode lockMode, ILoadable rootPersister, ISessionImplementor session, CancellationToken cancellationToken)
   at NHibernate.Loader.Loader.InstanceNotYetLoadedAsync(DbDataReader dr, Int32 i, ILoadable persister, EntityKey key, LockMode lockMode, EntityKey optionalObjectKey, Object optionalObject, IList hydratedObjects, ISessionImplementor session, CancellationToken cancellationToken)
   at NHibernate.Loader.Loader.GetRowAsync(DbDataReader rs, ILoadable[] persisters, EntityKey[] keys, Object optionalObject, EntityKey optionalObjectKey, LockMode[] lockModes, IList hydratedObjects, ISessionImplementor session, Boolean mustLoadMissingEntity, Action`2 cacheBatchingHandler, CancellationToken cancellationToken)
   at NHibernate.Loader.Loader.GetRowFromResultSetAsync(DbDataReader resultSet, ISessionImplementor session, QueryParameters queryParameters, LockMode[] lockModeArray, EntityKey optionalObjectKey, IList hydratedObjects, EntityKey[] keys, Boolean returnProxies, IResultTransformer forcedResultTransformer, QueryCacheResultBuilder queryCacheResultBuilder, Action`2 cacheBatchingHandler, CancellationToken cancellationToken)
   at NHibernate.Loader.Loader.DoQueryAsync(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies, IResultTransformer forcedResultTransformer, QueryCacheResultBuilder queryCacheResultBuilder, CancellationToken cancellationToken)
   at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollectionsAsync(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies, IResultTransformer forcedResultTransformer, QueryCacheResultBuilder queryCacheResultBuilder, CancellationToken cancellationToken)
   at NHibernate.Loader.Loader.DoListAsync(ISessionImplementor session, QueryParameters queryParameters, IResultTransformer forcedResultTransformer, QueryCacheResultBuilder queryCacheResultBuilder, CancellationToken cancellationToken)

Test NHibernate.zip

[nfplee]

Thanks, I'm glad you can reproduce.

Also you don't need to rewrite existing mappings. Instead of writing mapper.Class ...) you can reuse existing mapping class via mapper.AddMapping() or mapper.AddMapping()

Yeah I know but I found it easier to modify if it was all within 1 file.

[bahusoid]

Test case https://github.com/bahusoid/nhibernate-core/tree/gh3164. Not sure but seems regression from #1922

[bahusoid]

Fixed by #3171

[nfplee]

Great, thanks @bahusoid.