[BUG][Kotlin] Gson code in non-gson generation

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

Please see my comment below.

Generating from IntelliJ using the following configuration leads to unexpected Gson code to be in the generated result.

I think you forgot the following conditions:
{{#generateOneOfAnyOfWrappers}}
{{#gson}}

in these files:
modules/openapi-generator/src/main/resources/kotlin-client/anyof_class.mustache
modules/openapi-generator/src/main/resources/kotlin-client/oneof_class.mustache

Before you generate the Gson based TypeAdapter.

What do you think??

Originally posted by @sebastianblesgen in https://github.com/OpenAPITools/openapi-generator/issues/18965#issuecomment-2593473646

openapi-generator version

7.7.0

OpenAPI declaration file content or url

Generation Details

generateOneOfAnyOfWrappers=false
library=jvm-retrofit2
idea=true
serializationLibrary=moshi

Steps to reproduce

Using IntelliJ and generator V7 and the options specified above, I unexpectedly got some files with Gson dependencies.

Related issues/PRs

Suggest a fix

Add

{{#generateOneOfAnyOfWrappers}}
{{#gson}}
in

modules/openapi-generator/src/main/resources/kotlin-client/anyof_class.mustache
modules/openapi-generator/src/main/resources/kotlin-client/oneof_class.mustache

Start with modules/openapi-generator/src/main/resources/kotlin-client/anyof_class.mustache and oneof_class.mustache, using the reported IntelliJ configuration: generateOneOfAnyOfWrappers=false, library=jvm-retrofit2, and serializationLibrary=moshi. Check the conditions around generated Gson TypeAdapters. Done means generation with these settings no longer includes unexpected Gson dependencies.