First of all, what is the expected behaviour of having a field in dynamically built form, annotated like

/**
 * @Annotation\Required(false)
 * @Annotation\AllowEmpty()
 * @Annotation\ComposedObject("SomeObject")
 */

Should the field then be optional but SomeObject validated fully when present?

Second part is more of a bug I think. When you take above annotation and switch the order of @Annotation like

/**
 * @Annotation\ComposedObject("SomeObject")
 * @Annotation\Required(false)
 * @Annotation\AllowEmpty()
 */

then AnnotationBuilder fails to build the form with the exception:
Zend\InputFilter\Factory::createInput expects an array or Traversable; received "boolean"

I didn't find any in depth documentation / FAQ / tutorial about using ComposedObject with other annotations but it seems as if:

1. Form object that is built with AnnotationBuilder does not take Required and AllowEmpty into consideration when ComposedObject is present.
2. When using AllowEmpty / Required(false) with ComposedObject, the composed object specified gets validated regardless if it's present (and obviously fails if it's not).
3. Switching order of annotations confuses Zend\Form\Factory::createInputFilter(). $inputFilterSpecification argument contains the SomeObject definition but it also has required = false and allow_empty = true keys. Iterating inputFilterSpecification passes $value = false to Zend\Form\Factory::createInput($value) which refuses to work with false value.

If my explaination is vague, maybe the example could be helpful stackoverflow question