Validation can't be used when FieldArgs is an inner classes

[Mortimerp9]

If the FieldArgs argument class is defined as an inner class, sumac is ok with it. For instance, with:

import com.quantifind.sumac._
class MyClass {
    class MyArgs extends FieldArgs {
        var test: String = _
    }
}

we can do:

val c = new MyClass
val arg = new c.MyArgs
arg.parse(Map("test"->"test"))

and everything seems to be working.

However, when using annotation for validation:

import com.quantifind.sumac._
import com.quantifind.sumac.validation.Required
class MyClass {
    class MyArgs extends FieldArgs {
        @Required
        var test: String = _
    }
}

parse will throw an exception:

val c = new MyClass
val arg = new c.MyArgs
arg.parse(Map("test"->"test"))

java.util.NoSuchElementException: key not found: test
    at scala.collection.MapLike$class.default(MapLike.scala:228)
    at scala.collection.AbstractMap.default(Map.scala:58)
    at scala.collection.MapLike$class.apply(MapLike.scala:141)
    at scala.collection.AbstractMap.apply(Map.scala:58)
    at com.quantifind.sumac.FieldArgs$$anonfun$addAnnotationValidations$1.apply(FieldArgs.scala:56)
    at com.quantifind.sumac.FieldArgs$$anonfun$addAnnotationValidations$1.apply(FieldArgs.scala:55)
    at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
    at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:108)
    at com.quantifind.sumac.FieldArgs$class.addAnnotationValidations(FieldArgs.scala:55)
    at MyClass$MyArgs.addAnnotationValidations(<console>:12)
    at com.quantifind.sumac.FieldArgs$$anonfun$1.applyOrElse(FieldArgs.scala:18)
    at com.quantifind.sumac.FieldArgs$$anonfun$1.applyOrElse(FieldArgs.scala:15)
    at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:33)
    at scala.collection.TraversableLike$$anonfun$collect$1.apply(TraversableLike.scala:278)
    at scala.collection.immutable.List.foreach(List.scala:318)
    at scala.collection.TraversableLike$class.collect(TraversableLike.scala:278)
    at scala.collection.AbstractTraversable.collect(Traversable.scala:105)
    at com.quantifind.sumac.FieldArgs$class.getArgs(FieldArgs.scala:15)
    at MyClass$MyArgs.getArgs(<console>:12)
    at MyClass$MyArgs.getArgs(<console>:12)
    at com.quantifind.sumac.Args$class.getArgs(Args.scala:7)
    at MyClass$MyArgs.getArgs(<console>:12)
    at com.quantifind.sumac.Args$class.parser(Args.scala:28)
    at MyClass$MyArgs.parser$lzycompute(<console>:12)
    at MyClass$MyArgs.parser(<console>:12)
    at com.quantifind.sumac.Args$class.parse(Args.scala:39)
    at MyClass$MyArgs.parse(<console>:12)

[squito]

The reason for this is that Sumac figures out default values by calling the default (zero-arg) constructor, and grabbing the values from all fields.

However, inner-classes don't actually have a zero-arg constructor -- they really take a reference to the containing class (which java / scala normally take care of for you).

I don't know if there is anything we can do about this ... maybe the only TODO here is to update the docs to say you can't use inner classes. I'd definitely love to hear any ideas on how to fix.