[Bug]: Polymorphic types don't include composite schema reference

[emolina-collibra]

Description of the problem/issue

This project illustrates the problem. When having polymorphic types and using the swagger-gradle-plugin to generate the OpenAPI descriptor file, subtypes are missing the combined schema reference (allOf) to the parent type.

This is the current output in 2.2.41:

"DateAttributeTypeImpl" : {
  "type" : "object",
  "properties" : { }
}

And this was the expected output in 2.2.40:

"DateAttributeTypeImpl" : {
  "type" : "object",
  "allOf" : [ {
    "$ref" : "#/components/schemas/AttributeType"
  } ]
}

I debugged and the first pass of the model resolver for the parent type populates the reference correctly, however the model is redefined here and the reference is lost. I don't know enough of the model resolution to isolate a fix.

I suspect it might be a regression introduced while resolving #5003

Affected Version

2.2.41

Earliest version the bug appears in (if known):
2.2.41

Steps to Reproduce

Expand the project attached and execute:

./gradlew clean resolve

In order to compare the differences between 2.2.41 and 2.2.40, modify the gradle script to downgrade the dependency to swagger-core.

Expected Behavior

Subtypes should include a composite schema to the parent type like so

"DateAttributeTypeImpl" : {
  "type" : "object",
  "allOf" : [ {
    "$ref" : "#/components/schemas/AttributeType"
  } ]
}

Actual Behavior

Subtypes are created as independent models with no reference to the parent:

"DateAttributeTypeImpl" : {
  "type" : "object",
  "properties" : { }
}

Logs / Stack Traces

none

Additional Context

Checklist

• I have searched the existing issues and this is not a duplicate.
• I have provided sufficient information for maintainers to reproduce the issue.

[xeulbn]

From analyzing the resolution flow, it looks like the issue happens when the same subtype model is resolved more than once.

The initial resolution correctly creates a composed schema with an allOf reference to the parent.
However, a subsequent resolution of the subtype appears to redefine the model and overwrite the previously composed schema with a plain object schema.

This would explain why the subtype loses its allOf reference, and suggests that the issue is related to the model override logic rather than resolveSubtypes.

If this aligns with your understanding, I’d be happy to take a look at this issue and propose a fix.

[emolina-collibra]

From analyzing the resolution flow, it looks like the issue happens when the same subtype model is resolved more than once.

The initial resolution correctly creates a composed schema with an allOf reference to the parent. However, a subsequent resolution of the subtype appears to redefine the model and overwrite the previously composed schema with a plain object schema.

This would explain why the subtype loses its allOf reference, and suggests that the issue is related to the model override logic rather than resolveSubtypes.

If this aligns with your understanding, I’d be happy to take a look at this issue and propose a fix.

Correct it's been a while since i looked at the code but i recall i got to the same conclusion.

[xeulbn]

Hi,

While reviewing the fix in commit 7e51a74, I noticed something that might be worth double-checking.
It looks like model is reassigned to a ref-only Schema before attempting to read model.getAllOf(), getAnyOf(), and getOneOf().

Since a ref-only schema would not contain the original composition keywords, wouldn't this result in null being read in most cases? Would it be safer to preserve the original model in a separate variable (e.g., Schema original = model) and copy the composition fields from that before overwriting model? Also, could you confirm whether this issue has been officially resolved in swagger-core, or if it is still open for further work?

Just wanted to make sure I understand the current status correctly.