[AlexVarchuk]

What/Why/How?

Fixes a regression from 1.7.8: a recursive $ref inside allOf was sampled as null instead of {}. It happens in OpenAPI 3.0 and 3.1.

openapi: 3.0.0
components:
  schemas:
    MenuItem:
      type: object
      properties:
        name:
          type: string
        friend:
          allOf:
            - $ref: '#/components/schemas/MenuItem'

Sample of MenuItem:

Version	Result
1.7.6	{ "name": "string", "friend": { "name": "string", "friend": {} } }
1.7.8	{ "name": "string", "friend": { "name": "string", "friend": null } }

In 1.7.8, allOf passes a $ref item to traverse as the same object each time, so the identity-based cycle check catches it before the $ref cycle check runs. Since inferType({ $ref }) has no type, the result is null. Passing a copy ({ ...subSchema }) restores the $ref cycle check, which returns {}. The 1.7.8 change stays: no type is added to $ref items.

Reference

Found by the Redoc visual e2e test in https://github.com/Redocly/redocly/pull/30990

Testing

• New test: a recursive $ref inside allOf samples as {} in OpenAPI 3.0 and 3.1.
• Compared against 1.7.6 on 38 real specs (10,002 samples): identical with every spec forced to 3.0; with real versions only the intended $ref sibling changes remain.

Check yourself

• Code is linted
• Tested
• All new/updated code is covered with tests

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines