Strategy that extends OneOf so that each variant also refers back to the base type schema using allOf. This approach is sometimes referred to in OpenAPI 3 as a way to model polymorphism.

• compatible with OpenAPI clients that don't handle oneOf properly
• more complex schemas in Swagger UI

Using the Pet example above, this strategy yields the following:

"schemas": {
  "Pet": {
    "oneOf": [
      { "$ref": "#/components/schemas/Cat" },
      { "$ref": "#/components/schemas/Lizard" }
    ],
    "discriminator": {
      "propertyName": "type",
      "mapping": {
        "Cat": "#/components/schemas/Cat",
        "Lizard": "#/components/schemas/Lizard"
      }
    }
  },

  "Cat": {
    "allOf": [
      { "$ref": "#/components/schemas/Pet" },
      {
        "type": "object",
        "properties": {
          "type": {
            "type": "string",
            "enum": [ "Cat" ]
          },
          "name": {
            "type": "string"
          }
        },
        "required": [
          "type",
          "name"
        ]
      }
    ]
  },

  "Lizard": {
    "allOf": [
      { "$ref": "#/components/schemas/Pet" },
      {
        "type": "object",
        "properties": {
          "type": {
            "type": "string",
            "enum": [ "Lizard" ]
          },
          "lovesRocks": {
            "type": "boolean"
          }
        },
        "required": [
          "type",
          "lovesRocks"
        ]
      }
    ]
  }
}