[Kotlin-client] fix kotlin code client generator for oneOf with allOf

[bykakashka]

Removed children params from parent model in case of oneOf + allOf usage. Fixes #24164

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---

Summary by cubic

Fixes Kotlin client codegen for polymorphic oneOf + allOf with discriminators by stopping child properties from leaking into the parent model. Works consistently with jackson, moshi, gson, and kotlinx_serialization.

• Bug Fixes
  • Set skipOneOfPropertyMergeInParent = true in KotlinClientCodegen (constructor) for all serializers; moved the flag from AbstractKotlinCodegen and decoupled it from supportsInheritance.
  • Simplified DefaultCodegen so oneOf/anyOf are treated as alternatives when the flag is on (no child-property merge into parents regardless of discriminator or supportsInheritance); added parameterized tests across all serializers covering: plain oneOf wrapper, oneOf with discriminator (no leak), plain allOf (inheritance preserved), and allOf with discriminator (no leak).

^{Written for commit 646e880. Summary will update on new commits.}

[cubic-dev-ai]

3 issues found across 4 files

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[cubic-dev-ai]

1 issue found across 4 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java:311">
P2: Setting `skipOneOfPropertyMergeInParent = true` unconditionally in the KotlinClientCodegen constructor affects all oneOf/anyOf schemas, not just the oneOf+allOf case described in the PR. In `DefaultCodegen.addProperties()`, this flag prevents merging oneOf AND anyOf child properties into parent models globally. Since KotlinClientCodegen only supports oneOf/anyOf wrappers for `jvm-retrofit2` with `gson`/`kotlinx_serialization`, and the default is `jvm-okhttp4` with `moshi`, plain oneOf/anyOf schemas under default or unsupported configurations may lose child properties with no wrapper fallback. Consider scoping this flag to the specific oneOf+allOf/discriminator case or to library/serialization combinations that provide wrapper support.</violation>
</file>

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

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Setting skipOneOfPropertyMergeInParent = true unconditionally in the KotlinClientCodegen constructor affects all oneOf/anyOf schemas, not just the oneOf+allOf case described in the PR. In DefaultCodegen.addProperties(), this flag prevents merging oneOf AND anyOf child properties into parent models globally. Since KotlinClientCodegen only supports oneOf/anyOf wrappers for jvm-retrofit2 with gson/kotlinx_serialization, and the default is jvm-okhttp4 with moshi, plain oneOf/anyOf schemas under default or unsupported configurations may lose child properties with no wrapper fallback. Consider scoping this flag to the specific oneOf+allOf/discriminator case or to library/serialization combinations that provide wrapper support.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java, line 311:

<comment>Setting `skipOneOfPropertyMergeInParent = true` unconditionally in the KotlinClientCodegen constructor affects all oneOf/anyOf schemas, not just the oneOf+allOf case described in the PR. In `DefaultCodegen.addProperties()`, this flag prevents merging oneOf AND anyOf child properties into parent models globally. Since KotlinClientCodegen only supports oneOf/anyOf wrappers for `jvm-retrofit2` with `gson`/`kotlinx_serialization`, and the default is `jvm-okhttp4` with `moshi`, plain oneOf/anyOf schemas under default or unsupported configurations may lose child properties with no wrapper fallback. Consider scoping this flag to the specific oneOf+allOf/discriminator case or to library/serialization combinations that provide wrapper support.</comment>

<file context>
@@ -307,6 +307,8 @@ public KotlinClientCodegen() {
         cliOptions.add(CliOption.newBoolean(USE_JACKSON_3,
             "Use Jackson 3 dependencies (tools.jackson package). Not yet supported for kotlin-client; reserved for future use."));
+
+        skipOneOfPropertyMergeInParent = true;
     }
 
</file context>

[bykakashka]

The bug affects all serialization libraries equally. Without the fix, moshi, gson, and kotlinx_serialization all produce identical broken output — fat parent interfaces with leaked child properties and sibling contamination.

Plain oneOf without discriminator is NOT affected. These schemas generate a data class wrapper (not an interface), and addProperties() merging is correct — the wrapper IS supposed to contain all variant properties as a union type. Tested and confirmed.

Plain allOf without discriminator is NOT affected. Standard inheritance works identically with and without the fix.

Added 16 new parameterized tests covering all 4 patterns (plain oneOf, oneOf+discriminator, plain allOf, allOf+discriminator) × all 4 serialization libraries (jackson, moshi, gson, kotlinx_serialization) — all pass. The flag is safe to set unconditionally at the KotlinClientCodegen level.

[cubic-dev-ai]

1 issue found across 1 file (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java:311">
P2: Setting `skipOneOfPropertyMergeInParent = true` unconditionally in the KotlinClientCodegen constructor affects all oneOf/anyOf schemas, not just the oneOf+allOf case described in the PR. In `DefaultCodegen.addProperties()`, this flag prevents merging oneOf AND anyOf child properties into parent models globally. Since KotlinClientCodegen only supports oneOf/anyOf wrappers for `jvm-retrofit2` with `gson`/`kotlinx_serialization`, and the default is `jvm-okhttp4` with `moshi`, plain oneOf/anyOf schemas under default or unsupported configurations may lose child properties with no wrapper fallback. Consider scoping this flag to the specific oneOf+allOf/discriminator case or to library/serialization combinations that provide wrapper support.</violation>
</file>

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Re-trigger cubic</sub>