[BUG] Kotlin generator produces invalid code when allOf is used

[BUG] Kotlin generator produces invalid code when allOf is used

• 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

The Kotlin generator produces invalid code when using allOf in the Spec

Actual

data class Bird (

    @field:JsonProperty("id")
    override val id: java.util.UUID,

    @field:JsonProperty("featherType")
    val featherType: kotlin.String

) : Animal()

Expected

data class Bird (

    @field:JsonProperty("id")
    override val id: java.util.UUID,

    @field:JsonProperty("featherType")
    val featherType: kotlin.String

) : Animal

The generated code for the class Bird is attempting to call the constructor on the Animal interface it is implementing. Kotlin interfaces do not have constructors.

openapi-generator version

The bug exists using 5.3.0, the issue is not present in 5.2.1

OpenAPI declaration file content or url

openapi: 3.0.1
info:
  title: Example
  description: An example
  version: '0.1'
  contact:
    email: contact@example.org
    url: 'https://example.org'
servers:
  - url: http://example.org
tags:
  - name: bird
paths:
  '/v1/bird/{id}':
    get:
      tags:
        - bird
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/bird'
      operationId: get-bird
    parameters:
      - schema:
          type: string
          format: uuid
        name: id
        in: path
        required: true
components:
  schemas:
    animal:
      title: An animal
      type: object
      properties:
        id:
          type: string
          format: uuid
      required:
        - id
      discriminator:
        propertyName: type
        mapping:
          BIRD: '#/components/schemas/bird'
    bird:
      title: A bird
      type: object
      allOf:
        - $ref: '#/components/schemas/animal'
        - properties:
            featherType:
              type: string
          required:
            - featherType

Generation Details

Use openapi-generator-cli version 5.3.0

#!/bin/sh

openapi-generator-cli generate \
--generator-name kotlin \
--input-spec schema.yaml \
--output output \
--config config.yaml \
--template-dir templates \
--ignore-file-override .openapi-generator-ignore

All supporting files (including this script) are contained in the attached file issue.zip

Steps to reproduce

1. unzip issue.zip
2. cd issue; ./generate.sh
3. Observe the generated file
   • output/generated/com/example/api/models/Bird.kt

Related issues/PRs

N/A

Suggest a fix

The bug exists in 5.3.0, the issue is not present in 5.2.1

Start with the attached issue.zip, inspect schema.yaml and run generate.sh with openapi-generator-cli 5.3.0. Compare output/generated/com/example/api/models/Bird.kt with the expected Kotlin output, confirming that generation for the allOf example no longer attempts to call a constructor on the Animal interface.