Nested class fails to map about salat HOT 9 CLOSED

I created a spec showing this fails with pendingUntilFixed.

As a workaround: declare your case classes outside of the trait - in this example, Employee lives outside of ModelCtx and must be imported in TestApp. Then use grater[Employee] and that should work.

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Rafał , just out of interest, are you using a web framework of some type? I'm not familiar with this pattern and wanted to see where it fits in to your usage case, and maybe test it out with this framework directly and offer support for it if I can.

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This structure is a result of using cake pattern to achieve dependency injection:
http://lamp.epfl.ch/~odersky/papers/ScalableComponent.pdf
http://jonasboner.com/2008/10/06/real-world-scala-dependency-injection-di.html
I am using Unfiltered as web framework but it does not enforce such a structure.

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Won't fix. Due to how Scala handles a case class nested in another class, it creates a chicken and egg problem where is it not possible to get the companion object and class the grater needs in a usable form.

For instance,
scala> val g = grater[SomeTrait#NestedCaseClassInATrait]
g: com.novus.salat.Grater[com.novus.salat.test.model.SomeTrait#NestedCaseClassInATrait] = Grater(class com.novus.salat.test.model.SomeTrait$NestedCaseClassInATrait @ com.novus.salat.global.package$$anon$1@7cec59b)

Note that the sole constructor expects a reference to the outer trait:
scala> g.clazz.getConstructors.head
res4: java.lang.reflect.Constructor[_] = public com.novus.salat.test.model.SomeTrait$NestedCaseClassInATrait(com.novus.salat.test.model.SomeTrait,java.lang.String,scala.Option,scala.Option)

Meanwhile, the innter class companion class requires an actual backref to outer trait:
scala> val outer = g.clazz.companionClass.getDeclaredFields.head
outer: java.lang.reflect.Field = private final com.novus.salat.test.model.SomeTrait com.novus.salat.test.model.SomeTrait$NestedCaseClassInATrait$.$outer

And finally, the apply looks promising but it is bad candy. You can't actually invoke it - you have to use the one that requires the backref we can't provide:
scala> g.companionClass.getMethods.filter(_.getName == "apply").head
res15: java.lang.reflect.Method = public com.novus.salat.test.model.SomeTrait$NestedCaseClassInATrait com.novus.salat.test.model.SomeTrait$NestedCaseClassInATrait$.apply(java.lang.String,scala.Option,scala.Option)

Sigh.
scala> g.companionClass.newInstance
java.lang.InstantiationException: com.novus.salat.test.model.SomeTrait$NestedCaseClassInATrait$

Sorry, Rafał, I tried! It's just not possible for us to support this pattern verbatim. However, if you declare your case classes without nesting them in an outer class, you can use Salat.

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Thanks for your efforts to solve it. Fortunately this is not that problematic to have case classes outside of the trait. The only missed feature with this approach is that one won't be able to reference injected classes from entity case class methods (no DI inside entity classes).

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Yes, I feel very bad about that. I haven't abandoned the topic 100%: I was considering making a post of some type, maybe StackOverflow, asking how serialization back to object could ever be expected to work in Cake pattern without some heavy duty Java reflection given the constraints Scala imposed on inner classes.

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How about using copy method on case class. User of the Salat would provide some instance of the case class and grater would use copy operation on it to generate new instance. It is not very elegant but maybe this will allow to avoid this circular dependency. What do you think?

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Alas, our problem is that we are de-serializing from something else back to a case class, and don't have a handy instance of the case class hanging around... :) That's what we're trying and failing to get from the companion class and companion object.

By the end of the weekend I will try to write up a wiki page explaining the problem in more detail and make a posting to the Salat google group asking for help to find a solution.

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But the idea is that client will provide this handy instance. Grater API would for example work like that:

val fakeEmployee = Employee("Frank", e) 
grater(fakeEmployee).asObject(dboToTransform)

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