[rm127]

Summary

Addresses #11552.
Related to #12065; this does not add a dedicated Quarkus generator.

Adds configurable inheritance handling to kotlin-server so discriminator-based models can compile and round-trip through Jackson, including with jaxrs-spec.

• inheritanceMode=none|sealed|abstract|composition; defaults to abstract for JAX-RS and sealed for Ktor/Javalin. Invalid combinations are rejected.
• JAX-RS abstract parents and children preserve inherited optional-property nullability, constructor forwarding and discriminator mappings without duplicating the discriminator in JSON.
• Required nullable properties accept null but require JSON presence; required non-null properties reject explicit null, including primitives. Nullable properties do not receive @NotNull.
• Nullable responses and bodyless Mutiny responses retain nullable Kotlin types.

none is non-polymorphic; composition produces wrappers rather than wire-compatible polymorphism. Discriminated object allOf/oneOf/anyOf hierarchies are covered; arbitrary JSON Schema unions and missing-versus-null tracking are not.

Verification

45 targeted generator tests pass, including nested discriminator inheritance, flat union models, configured visibility, compilation across supported JAX-RS modes with serialization enabled/disabled, discriminator round trips and invalid-input rejection. Checkstyle passes. Regression fixtures are synthetic; no application-specific code or contracts are included.

See the JAX-RS guide for nullability semantics and limitations; the option reference is generated from the code.

PR checklist

• Read the contribution guidelines.
• Run the full project build, regenerate all affected samples and export generator documentation. Targeted reactor builds/tests and generator documentation updates are complete; the full repository-wide regeneration has not been run.
• Request review from the Kotlin technical committee.

[cubic-dev-ai]

3 issues found across 7 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[wing328]

thanks for the PR

cc @karismann (2019/03) @Zomzog (2019/04) @andrewemery (2019/10) @4brunu (2019/11) @yutaka0m (2020/03) @stefankoppier (2022/06) @e5l (2024/10) @dennisameling (2026/02)

[wing328]

please review the build failure and the feedback from cubic-dev-ai when you've time.

[cubic-dev-ai]

1 issue found across 3 files (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[rm127]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

Thanks for the heads up! I've altered the history to reflect my GH user

[jpfinne]

@rm127 I don't use Kotlin...
Can't INHERITANCE_MODE_NONE and INHERITANCE_MODE_COMPOSITION be done in the OpenApiNormalizer?

Then all languages can use the feature

Just my 2 cents

[rm127]

@jpfinne

@rm127 I don't use Kotlin... Can't INHERITANCE_MODE_NONE and INHERITANCE_MODE_COMPOSITION be done in the OpenApiNormalizer?

Then all languages can use the feature

Just my 2 cents

I'm not sure I follow how these would be relevant in the normalization stage? Furthermore I don't think having the different "modes" split across multiple classes helps with readability.

[rm127]

Following up after roughly three months: I revisited this PR while validating an end-to-end Kotlin/JAX-RS migration, rather than just inspecting the generated source.

Compiling and exercising the generated models exposed gaps in the original implementation: optional inherited properties could have incompatible nullability, discriminated unions were not consistently emitted as usable Jackson hierarchies, and required-nullable fields and bodyless Mutiny responses needed their Kotlin/JSON semantics preserved.

The new commit addresses those findings and adds synthetic compilation and Jackson regression tests. This is a correctness follow-up to the original inheritance work, not a rebase or unrelated cleanup.

44 targeted generator tests and Checkstyle pass. The PR description now states the supported modes, limitations and remaining repository-wide checks explicitly.

[cubic-dev-ai]

All reported issues were addressed across 14 files

<sub>Reply with feedback, questions, or to request a fix.

View guided diff | Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 7 files (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

View guided diff | Re-trigger cubic</sub>