Should properties be valid at the same level as allOf?

[victorsc]

I noticed that the following schema is considered valid by the Swagger Editor and other OpenAPI tools:

Dog:
  allOf: 
  - $ref: "#/components/schemas/Pet"
  properties:
    bark:
      type: boolean
    breed:
      type: string
      enum: [Dingo, Husky, Retriever, Shepherd]

However, according to my understanding of OpenAPI specifications:

• The properties keyword should not be valid at the same level as allOf.

allOf takes an array of object definitions that are used for independent validation but together compose a single object.

• The correct way to structure this should be:

Dog: # "Dog" is a value for the pet_type property (the discriminator value)
  allOf:
    - $ref: "#/components/schemas/Pet"
    - type: object
      properties:
        bark:
          type: boolean
        breed:
          type: string
          enum: [Dingo, Husky, Retriever, Shepherd]

Questions for OpenAPI maintainers:

1. Is this behavior intentional? Should properties be allowed at the same level as allOf, or is this a parsing mistake in tools like Swagger Editor?
2. If this is valid, could you point to the relevant section in the OpenAPI 3.0/3.1 specification that explicitly allows properties at the same level as allOf?
3. If it is a mistake, should Swagger Editor and other OpenAPI tools enforce stricter validation to prevent incorrect schema definitions?

I would appreciate any clarification on this matter. Thanks for your help! 🚀

[ralfhandl]

Placing allOf and properties next to each other is common use in JSON Schema, see this example in the JSON Schema Core specification: https://json-schema.org/draft/2020-12/json-schema-core#name-references-and-generative-u

This is not specific to OpenAPI or OpenAPI tools.

[victorsc]

Thanks for the clarification and the reference! That clears it up. Closing the issue now.