Duplicate (nested) discriminator union values not allowed

[maxboone]

Take, for example, a collection of pets:

type RedCat = { color: "red" };
type AshCat = { color: "ash" };

/**
 * @discriminator color
 */
type Cat = AshCat | RedCat;

/**
 * @discriminator animal
 */
type Pet = (
    ({ animal: "cat" } & Cat)
    | ({ animal: "dog" })
);

This yields an error that there are "Duplicate discriminator values: cat", which makes sense, as there are now two elements that match the "animal" tag. Not passing a discriminator will yield a (fairly flat) JSON Schema, but I like using the if-else statements for better error messages and more readability of the schema.

I'd expect something like the following to be possible to generate, by extending the current logic:

{
  "$ref": "#/definitions/Pet",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "definitions": {
    "Pet": {
      "allOf": [
        {
          "if": {
            "properties": {
              "animal": {
                "const": "cat",
                "type": "string"
              }
            }
          },
          "then": {
            "$ref": "#/definitions/Cat"
          }
        },
        {
          "if": {
            "properties": {
              "animal": {
                "const": "dog",
                "type": "string"
              }
            }
          },
          "then": {
            "$ref": "#/definitions/Dog"
          }
        }
      ],
      "properties": {
        "animal": {
          "type": "string",
          "enum": ["dog", "cat"]
        }
      },
      "required": ["animal"],
      "type": "object"
    },
    "Dog": {
      "type": "object"
    },
    "Cat": {
      "allOf": [
        {
          "if": {
            "properties": {
              "color": {
                "const": "red",
                "type": "string"
              }
            }
          },
          "then": {
            "$ref": "#/definitions/RedCat"
          }
        },
        {
          "if": {
            "properties": {
              "color": {
                "const": "ash",
                "type": "string"
              }
            }
          },
          "then": {
            "$ref": "#/definitions/AshCat"
          }
        }
      ],
      "properties": {
        "color": {
          "type": "string",
          "enum": ["ash", "red"]
        }
      },
      "required": ["color"],
      "type": "object"
    },
    "RedCat": {
      "type": "object"
    },
    "AshCat": {
      "type": "object"
    }
  }
}

I would, in this case, add some recursive logic that also applies the if-then constants to the leafs so that they can disable additional properties for better type checking.