[KOTLIN-SPRING;JAVA-SPRING] bugfix: update JsonInclude annotations for optional+nullable fields to handle serialization correctly when openApiNullable = true

[Picazsoo]

Fix: @JsonInclude(NON_ABSENT) for JsonNullable fields in kotlin-spring and java-spring generators

Issue

When openApiNullable=true, optional+nullable fields are generated as JsonNullable<T> but without any @JsonInclude annotation. This means JsonNullable.undefined() (the "absent" state) could be serialized into the JSON output, defeating the purpose of the three-state wrapper.

Fix

Added @field:JsonInclude(JsonInclude.Include.NON_ABSENT) to any field where x-is-jackson-optional-nullable is true, in dataClassOptVar.mustache. This ensures:

State	Serialized?
JsonNullable.undefined()	❌ excluded
JsonNullable.of(null)	✅ included as null
JsonNullable.of("value")	✅ included as "value"

This is a nasty bug that should be fixed - because someone using the generated clients for patch operations might be unknowingly deleting resources even when setting JsonNullable as undefined.

PR checklist

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• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request. - spring: @cachescrubber (2022/02) @welshm (2022/02) @MelleD (2022/02) @atextor (2022/02) @manedev79 (2022/02) @javisst (2022/02) @borsch (2022/02) @banlevente (2022/02) @Zomzog (2022/09) @martin-mfg (2023/08); kotlin: @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

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Summary by cubic

Fixes serialization of optional+nullable fields for kotlin-spring and java-spring when openApiNullable=true by adding @JsonInclude(JsonInclude.Include.NON_ABSENT) to org.openapitools.jackson.nullable.JsonNullable fields. Undefined values are omitted; nulls and concrete values are included.

• Bug Fixes
  • kotlin-spring: emit @field:JsonInclude(JsonInclude.Include.NON_ABSENT) in dataClassOptVar.mustache when x-is-jackson-optional-nullable is true.
  • java-spring: emit @JsonInclude(JsonInclude.Include.NON_ABSENT) in JavaSpring/pojo.mustache; ensure JsonInclude import in SpringCodegen.postProcessModelProperty for optional+nullable fields when openApiNullable=true.
  • Tests: expanded Java and Kotlin generator tests for openApiNullable true/false; added Kotlin runtime tests to verify undefined/null/value serialization.
  • Samples: regenerated Spring Boot and Spring HTTP Interface models to include NON_ABSENT on JsonNullable fields.

^{Written for commit 000a348. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

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[cubic-dev-ai]

No issues found across 7 files

_{Re-trigger cubic}