LINQ query dynamic component by interface hangs the application

[nfplee]

I have the following query which executes fine:

var posts = await session.Query<BlogPost>()
    .Where(p => p.Attributes["Field1"] != null)
   .ToListAsync();

However if I change it to use an interface instead then the query hangs.

var posts = await session.Query<IBlogPost>()
    .Where(p => p.Attributes["Field1"] != null)
    .ToListAsync();

Please see the attached application which helps demonstrate this. This problem only happens when filtering against an attribute.

ConsoleApp1.zip

[bahusoid]

Infinite loop

nhibernate-core/src/NHibernate/Linq/Visitors/VisitorUtil.cs

Lines 27 to 50 in 6c70217

	while (metaData == null && targetObject != null &&
	(targetObject.NodeType == ExpressionType.MemberAccess || targetObject.NodeType == ExpressionType.Parameter ||
	targetObject is QuerySourceReferenceExpression))
	{
	System.Type memberType;
	if (targetObject is QuerySourceReferenceExpression)
	{
	var querySourceExpression = (QuerySourceReferenceExpression) targetObject;
	memberType = querySourceExpression.Type;
	}
	else if (targetObject.NodeType == ExpressionType.Parameter)
	{
	var parameterExpression = (ParameterExpression) targetObject;
	memberType = parameterExpression.Type;
	}
	else //targetObject.NodeType == ExpressionType.MemberAccess
	{
	var memberExpression = ((MemberExpression) targetObject);
	memberPath = memberExpression.Member.Name + "." + memberPath;
	memberType = memberExpression.Type;
	targetObject = memberExpression.Expression;
	}
	metaData = sessionFactory.GetClassMetadata(memberType);
	}

Introduced in #237 (4.0.0.Alpha2)

[bahusoid]

It's not a regression. It didn't stuck before #237 but failed in some other way - dynamic components on unmapped interface never worked in LINQ

[nfplee]

@bahusoid do you have a suggestion for a temporary fix?

[nfplee]

I already tried looking into this as this is what I do for my components. However the Class method is not available in the ClassMapping class. Looking into the code for the Class method against the ComponentMapping I tried adding:

CustomizersHolder.AddCustomizer(typeof(IBlogPost), m => m.Class(typeof(BlogPost)));

But this had no effect.

[bahusoid]

this is what I do for my components. However the Class method is not available in the ClassMapping class. Lo

Indeed. It seems I thought of component mapping myself. You can try to specify EntityName(typeof(IBlogPost).FullName) in your class mapping - but it should(?) work only for queries on interface. It will stuck for class.

[nfplee]

Thanks @bahusoid that worked. Please note this doesn't fix the original issue, it just flips it so now when querying a dynamic component against the BlogPost class it hangs. This works better for me as my dynamic component is an attributes collection which allows me to dynamically add properties to my entities where I can't modify the concrete type, therefore I'm more likely to query the attributes against the IBlogPost abstraction.

[nfplee]

I've decided that the fix of using EntityName(typeof(IBlogPost).FullName) in the mapping is actually the correct way to go as now I don't need to add conventions for my abstractions.

I debated closing out this issue but I'll leave it open as it would be better to throw an exception than get stuck an infinite loop.