spec.json

{
  "swagger": "2.0",
  "info": {
    "version": "1.0.0",
    "title": "Sample API with x-nullable nested schema"
  },
  "host": "api.example.com",
  "basePath": "/v1",
  "schemes": ["https"],
  "paths": {
    "/items/{id}": {
      "get": {
        "summary": "Get a specific item",
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "type": "string"
          }
        ],
        "responses": {
          "200": {
            "description": "The requested item",
            "schema": {
              "$ref": "#/definitions/Item"
            }
          }
        }
      }
    }
  },
  "definitions": {
    "Item": {
      "type": "object",
      "required": ["name", "active_listing", "description"],
      "properties": {
        "name": {
          "type": "string"
        },
        "description": {
          "type": "string",
          "x-nullable": true
        },
        "active_listing": {
          "x-nullable": true,
          "$ref": "#/definitions/Listing"
        }
      }
    },
    "Listing": {
      "type": "object",
      "required": ["price", "currency", "seller"],
      "properties": {
        "price": {
          "type": "number",
          "format": "float"
        },
        "currency": {
          "type": "string"
        },
        "seller": {
          "type": "string"
        }
      }
    }
  }
}