[BUG] Kotlin generated code makes non-nullable shema fields nullable

[mobilekosmos]

Bug Report Checklist

• [x ] Have you provided a full/minimal spec to reproduce the issue?
• [ x] Have you validated the input using an OpenAPI validator (example)?
• [ ] Have you tested with the latest master to confirm the issue still exists?
• [x ] Have you searched for related issues/PRs?
• [ x] What's the actual output vs expected output?
• [ ] [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When I use the open-api-generator all of the model fields are ? nullable, all classes look like this:

data class PagedResultDtoOfStoredDeviceFilterWithoutTermDto (

    @Json(name = "currentPage")
    val currentPage: kotlin.Int? = null,

    @Json(name = "totalPages")
    val totalPages: kotlin.Int? = null,

    @Json(name = "pageSize")
    val pageSize: kotlin.Int? = null,

    @Json(name = "totalCount")
    val totalCount: kotlin.Int? = null,

    @Json(name = "items")
    val items: kotlin.collections.List<StoredDeviceFilterWithoutTermDto>? = null

)

Despite those fields are not all nullable in the swagger.json.

openapi-generator version

6.3.0

OpenAPI declaration file content or url

swagger.json

Generation Details

java -jar openapi-generator-cli.jar generate ^
     -g kotlin ^
     --library jvm-retrofit2 ^
     -i "https://app-hsm-clse-stage.azurewebsites.net/swagger/standardV1/swagger.json" ^
     -p groupId=com.mycompany ^
     -p artifactId=mycompany-myproduct-client-kotlin ^
     -p artifactVersion=1.0.0 ^
     -p basePackage=com.mycompany.myproduct.networking ^
     -p packageName=com.mycompany.myproduct.networking ^
     -p configPackage=com.mycompany.myproduct.networking.config ^
     -p apiPackage=com.mycompany.myproduct.networking.api ^
     -p modelPackage=com.mycompany.myproduct.networking.model ^
     -p sourceFolder=src/main/java ^
     -p dateLibrary=java8 ^
     -p java8=true ^
     -p useRxJava3=true ^

pause

Steps to reproduce

Run above batch file. Check all model classes. For example IDs are never nullable in our swagger.json, the generated code is always nullable, no matter which one.

Related issues/PRs

Suggest a fix

On SO somebody suggested a workaround, but I strongly think this is a bug.

[o-nix]

#

By default, all object properties are optional. You can specify the required properties in the required list

[mobilekosmos]

But the specification also has the nullable attribute for each data type, which is being ignored.

[mobilekosmos]

I understand now that a property which is not required must be handled as nullable on the client side, but maybe if this works as designed we could make a feature request out of this? We need to be able to configure this in the generator with a flag, I'm surprised I'm the first one to come up with this?