Resolving of discriminatorValues doesn't respect inheritance

[jenschude]

Following RAML definition:

#%RAML 1.0
---
title: Test
types:
  Reference:
    properties:
      typeId: string
      id: string
  FieldType:
    discriminator: name
    properties:
      name:
        type: string
  ReferenceFieldType:
    type: FieldType
    discriminatorValue: Reference
    properties:
      referenceTypeId:
        type: string
/type:
  get:
    responses:
      200:
        body:
          application/json:
            example: {
              "name": "Reference",
              "referenceTypeId": "channel"
            }
            type: FieldType

Results in following errors:

Missing required field "typeId"
Missing required field "id"

By just reordering the type definition a little bit like this:

#%RAML 1.0
---
title: Test
types:
  FieldType:
    discriminator: name
    properties:
      name:
        type: string
  ReferenceFieldType:
    type: FieldType
    discriminatorValue: Reference
    properties:
      referenceTypeId:
        type: string
  Reference:
    properties:
      typeId: string
      id: string
/type:
  get:
    responses:
      200:
        body:
          application/json:
            example: {
              "name": "Reference",
              "referenceTypeId": "channel"
            }
            type: FieldType

There are no validation errors anymore.

The reason for that is, that the parser first tries the first type either with a name or a discriminatorValue of Reference.

Also it's not directly specified that only discriminator values of inherited types should be considered. It makes a lot of sense for polymorph types to only take them into consideration as polymorph types should always be a subclass of the class defining the discriminator. This would resolve such issues like the above examples.

Aha! Link: https://mulesoft-roadmap.aha.io/features/APIRAML-78