[BUG][JAVA] Generator fails to create a working client with Springs HttpStatusCode involved

Bug Report Checklist

• [✅] Have you provided a full/minimal spec to reproduce the issue?
• [✅] Have you validated the input using an OpenAPI validator?
• [❌: I couldn't build the latest Snapshot due to proxy and corporate restrictions] Have you tested with the latest master to confirm the issue still exists?
• [✅] Have you searched for related issues/PRs?
• [expected: should not result in compile errors] What's the actual output vs expected output?
• [❌] [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Using the attached files will result in a non compiling generated client, as seen in the description of Steps to reproduce. This is the minimal example I could create. The actual use-case we have is, to use the attached ApiError class in a ControllerAdvice to react to errors of our services.

openapi-generator version

7.17.0

OpenAPI declaration file content or url

https://gist.github.com/coinzz/24597c69a8877d95e4f10fd681f28ee3

Generation Details

• Apache Maven 3.9.9
• openjdk 17.0.12 2024-07-16 LTS
• also with: openjdk 21.0.4 2024-07-16 LTS
• the rest is configured in the pom.xml

Steps to reproduce

1. Put the api-docs.json on the same level as the pom.xml
2. run mvn generate-sources
3. This will be succesful, but navigate to generated-sources\client\src\main\java\de\test\client\model\HttpStatus.java
4. See the Error:

Related issues/PRs

I couldn't find a direct related issue.

Suggest a fix

It seems that sealed classes or inheritance break the generation, but I am not sure if that is the concrete problem.

Start with the attached api-docs.json and pom.xml, then run mvn generate-sources and inspect generated-sources/client/src/main/java/de/test/client/model/HttpStatus.java. Trace the Java client generation path handling the Spring HttpStatusCode-related model and inheritance. Done means the generated client compiles without errors.