Unable to use schema inheritence

[mikaelkaron]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

5.2

Plugin version

5.2.0

Node.js version

22.9

Operating system

Linux

Operating system version (i.e. 20.04, 11.3, 10)

debian 12

Description

Schemas using model inheritance are not working correctly.

This schema

{
  "swagger": "2.0",
  "info": {
    "version": "9.4.0",
    "title": "@fastify/swagger"
  },
  "definitions": {
    "def-0": {
      "type": "object",
      "properties": {
        "parent": {
          "type": "string"
        }
      },
      "required": [
        "parent"
      ],
      "title": "schema:parent"
    },
    "def-1": {
      "$ref": "#/definitions/def-0",
      "type": "object",
      "properties": {
        "child": {
          "type": "string"
        }
      },
      "required": [
        "child"
      ],
      "unevaluatedProperties": false,
      "title": "schema:child"
    }
  },
  "paths": {
    "/parent": {
      "get": {
        "responses": {
          "200": {
            "description": "Default Response",
            "schema": {
              "$ref": "#/definitions/def-0"
            }
          }
        }
      }
    },
    "/child": {
      "get": {
        "responses": {
          "200": {
            "description": "Default Response",
            "schema": {
              "$ref": "#/definitions/def-1"
            }
          }
        }
      }
    }
  }
}

Will not render correctly in the UI

Link to code that reproduces the bug

https://github.com/mikaelkaron/json-schema-inherit-error/tree/fastify

Expected Behavior

Schema inheritance to work as expected

[Uzlopak]

unevaluatedProperties is not supported?

[mikaelkaron]

unevaluatedProperties is not supported?

That could be the problem. From the docs

unevaluatedProperties works by collecting any properties that are successfully validated when processing the schemas and using those as the allowed list of properties.

So that could be part of the problem.