[BUG] [kotlin-client] kotlinx_serialization deserialization fails on unexpected/unknown keys #13013

Description

Deserialization of a response with an unexpected key leads to the following error

kotlinx.serialization.json.internal.JsonDecodingException: Unexpected JSON token at offset 282: Encountered an unknown key 'card'. Use 'ignoreUnknownKeys = true' in 'Json {}' builder to ignore unknown keys.

openapi-generator version

6.0.1

Generation Details

using kotlinx_serialization as serialization library. gradle build specifics:

openApiGenerate {
    generatorName.set("kotlin")
    configOptions.set(
        mapOf(
            "serializationLibrary" to "kotlinx_serialization"
        )
    )
}

Related issues/PRs

#9755 – same fix added to kotlin-multiplatform solution already

Suggest a fix

Add ignoreUnknownKeys = true to jvmJson at the bottom of
https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/kotlin-client/jvm-common/infrastructure/Serializer.kt.mustache