OpenAPITools / OpenAPITools/openapi-generator

[BUG] [KOTLIN] simple data type of arrays is lost on implementing classes or discriminator interfaces

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Issue: Bug
Dominant language
Java
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Description

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?
  • [Optional] Sponsorship to speed up the bug fix or feature request (example)
Description

When generating data classes of an interface declaring properties having an array of primitive types, the resulting type of the list resolves to kotlin.Any and the code doesn't compile.
Same happens for discriminator interfaces.

openapi-generator version

7.5.0

OpenAPI declaration file content or url

https://gist.github.com/toggm/f8ea4f221a49ccb34b082fe1585b78b3

Generation Details
openapi-generator-cli 7.5.0
  commit : cce4139
  built  : -999999999-01-01T00:00:00+18:00
  source : https://github.com/openapitools/openapi-generator
  docs   : https://openapi-generator.tech/

Generated data class or interface is ok:

data class Interface(

    @Schema(example = "null", description = "")
    @get:JsonProperty("stringArrayProperty") val stringArrayProperty: kotlin.collections.List<kotlin.String>? = null,

    @Schema(example = "null", description = "")
    @get:JsonProperty("booleanArrayProperty") val booleanArrayProperty: kotlin.collections.List<kotlin.Boolean>? = null,

    @field:Valid
    @Schema(example = "null", description = "")
    @get:JsonProperty("objectArrayProperty") val objectArrayProperty: kotlin.collections.List<MyObject>? = null,

    @Schema(example = "null", description = "")
    @get:JsonProperty("type") val type: kotlin.String? = null

Generated data class for MyImpl lost type information:

data class MyImpl1(

    @field:Valid
    @Schema(example = "null", description = "")
    @get:JsonProperty("stringArrayProperty") val stringArrayProperty: kotlin.collections.List<kotlin.Any>? = null,

    @field:Valid
    @Schema(example = "null", description = "")
    @get:JsonProperty("booleanArrayProperty") val booleanArrayProperty: kotlin.collections.List<kotlin.Any>? = null,

    @field:Valid
    @Schema(example = "null", description = "")
    @get:JsonProperty("objectArrayProperty") val objectArrayProperty: kotlin.collections.List<MyObject>? = null,

Same for discriminator interface:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
@JsonSubTypes(
      JsonSubTypes.Type(value = MyImpl1::class, name = "impl1")
)

interface DiscriminatorInterface{
                @get:Schema(example = "null", description = "")
        val title: kotlin.String?

                @get:Schema(example = "null", description = "")
        val stringArrayProperty: kotlin.collections.List<kotlin.Any>?

                @get:Schema(example = "null", description = "")
        val booleanArrayProperty: kotlin.collections.List<kotlin.Any>?

                @get:Schema(example = "null", description = "")
        val objectArrayProperty: kotlin.collections.List<MyObject>?

                @get:Schema(example = "null", description = "")
        val type: kotlin.String?
}

Steps to reproduce
Related issues/PRs
Suggest a fix

Didn't find workaround so far.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the generated Kotlin models from the linked OpenAPI declaration with openapi-generator-cli 7.5.0, comparing the interface output with MyImpl1 and the discriminator interface. Trace the Kotlin generator path responsible for inherited array properties; done means primitive array element types remain String or Boolean instead of kotlin.Any and the generated code compiles.

Written by the indexing model from the issue text.

Assessment

Tech stack
kotlin
Domain
tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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