[BUG] [Kotlin] overriden variables are not generated with 'override' keyword

[Sylvain-maillard]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

• Given a openapi spec containing a Schema (Car) that inherits from another (Vehicle) using discriminator and allOf,
• and the Schema Vehicle define a property "x" of type "object",
• and the Schéma Car redefining the property by specializing the type to "string"
• when I generate the code, then the class Car won't compile because the redefined var x does not have the modifier override.

I expect the attributes of Car to have the override keyword as it is valid in kotlin to do that.

openapi-generator version

Tested on latest v7.17.0-SNAPSHOT.

OpenAPI declaration file content or url

see https://gist.github.com/Sylvain-maillard/fe3d0e25d4b21e6acfee8b0544da12e8

Generation Details

Issue was reproduce using docker without specific parameters except the kotlin generator.

docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli generate -i /local/issue.yaml -g kotlin -o /local/generated

Steps to reproduce

• generate the kotlin code using the provided yaml
• the overriden attributes of class Car misses the override keyword.

Related issues/PRs

Suggest a fix

I'have found a quick and dirty fix that rely on rescanning all schemas, looking for duplicate vars on each parents.

I've added the code in org.openapitools.codegen.languages.AbstractKotlinCodegen#postProcessAllModels

It's probably better to fix the issue when the CodegenProperty instances are created, but I didn't have time to dig in that.