Default field in schema object with type object

[mtovt]

Hello! Is it possible to specify a default object property for object, using default field?
For example I want to specify a default foo property in Bar object. I want to specify default Foo object only in the property of objects Bar. If it is possible, please provide an example.

openapi: 3.0.3
info:
  title: 'Example'
  version: 0.1.0
servers:
  - url: 'http://example.com'
paths:
  '/foo':
    delete:
      responses:
        '200':
          description: OK
components:
  schemas:
    Foo:
      type: object
      properties: 
        text:
          type: string
        number:
          type: number
    Bar:
      type: object
      properties:
        foo:
          allOf:
              - $ref: '#/components/schemas/Foo'
          default: "Is it possible to specify a default Foo object here?"

[flaksp]

Yes, it is possible.

OpenAPI 3.0 uses JSON Schema (draft 5) spec to define schemas.

The default keyword is defined in JSON Schema Validation spec, section 6.2:

There are no restrictions placed on the value of this keyword.

This keyword can be used to supply a default JSON value associated with a particular schema. It is RECOMMENDED that a default value be valid against the associated schema.

OpenAPI 3.0 clarifies semantics of the keyword in section 4.7.25.1 of the spec:

The default value represents what would be assumed by the consumer of the input as the value of the schema if one is not provided. Unlike JSON Schema, the value MUST conform to the defined type for the Schema Object defined at the same level. For example, if type is string, then default can be "foo" but cannot be 1.

It means you may use default keyword to document what default behaviour of your API would be like if value is omited, for example.

Your example may be modified as:

openapi: 3.0.3
info:
  title: Example
  version: 0.1.0
servers:
- url: http://example.com
paths:
  /foo:
    delete:
      responses:
        '200':
          description: OK
components:
  schemas:
    Foo:
      type: object
      properties:
        text:
          type: string
        number:
          type: number
    Bar:
      type: object
      properties:
        foo:
          allOf:
          - $ref: '#/components/schemas/Foo'
          default:
            text: abc
            number: 123

[mtovt]

Thank you for the explanation!

[handrews]

This was answered and accepted, closing.