OpenAPI: Fix Circular reference in specific order gives empty schema

[desjoerd]

OpenAPI: Fix Circular reference in specific order gives empty schema

In the ResolveReferenceForSchema method it could be that when executed in a certain order with a circular reference that it would register the schema without properties.

Description

In the ResolveReferenceForSchema method it now no longer registers schemas with a $ref as a full schema. They will eventually be registered as the method is recursive.

Fixes #63503

[desjoerd]

This was a head-scratcher 😅. The fun of recursive methods 😛.

[desjoerd]

@captainsafia I know it was yesterday, but I remember why it's in two seperate groups in the sample. If one of the property orders is correct the referencedmodel schema is emitted. So it's in the rare case when the circular reference is in the specific order, and the referenced model is not used in any other endpoint.

I will remove it from the sample (it's not really adding value there) and just create two seperate isolated unit tests in the schema service tests.

[captainsafia]

@desjoerd Sounds like a good plan to just use unit tests to validate this -- thanks!

[Copilot]

Pull Request Overview

This PR fixes a bug in the OpenAPI schema generation service where circular references processed in a specific order could result in empty schemas. The fix changes how schema references are handled to prevent premature registration of incomplete schemas.

Key changes:

• Modified the ResolveReferenceForSchema method to return a reference instead of registering the schema immediately
• Added comprehensive test coverage for circular reference scenarios with different property orders

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
OpenApiSchemaService.cs	Changed schema reference resolution to prevent premature registration of incomplete schemas
OpenApiSchemaService.SchemaReferences.cs	Added test cases covering circular reference scenarios with different property ordering

[desjoerd]

@captainsafia I've moved the tests 😊. Luckily the same methods where available so an easy change. Let me know if you prever them higher up or not.

I am not fond of #region but that unit tests file screams it a little bit 😅. Maybe something for the future when the fun starts around enabling Schema Reference transformations.