[BUG] [Kotlin-Spring]: Free-form parameter should not generate a @RequestParam annotation

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

Free-form query param spec generated spring @RequestParam annotation when it should not.

openapi-generator version

Using version 6.4.0

Technically not a regression since the issue which was supposed to fix it did fix it only partially (see #8080).

OpenAPI declaration file content or url

Could be reproduce with both definitions below

Inline schema definition

openapi: 3.0.0
servers:
  - url: 'localhost:8080'
info:
  version: 1.0.0
  title: OpenAPI Petstore
  license:
    name: Apache-2.0
    url: 'https://www.apache.org/licenses/LICENSE-2.0.html'
paths:
  /pony:
    get:
      operationId: list
      parameters:
        - in: query
          name: pageQuery
          schema:
            type: object
            additionalProperties:
              type: string

Separate schema definition

openapi: 3.0.0
servers:
  - url: 'localhost:8080'
info:
  version: 1.0.0
  title: OpenAPI Petstore
  license:
    name: Apache-2.0
    url: 'https://www.apache.org/licenses/LICENSE-2.0.html'
paths:
  /pony:
    get:
      operationId: list
      parameters:
        - in: query
          name: pageQuery
          required: false
          style: form
          explode: true
          schema:
            $ref: '#/components/schemas/SearchCriteria'

components:
  schemas:
    SearchCriteria:
      type: object
      additionalProperties:
        type: string

Generation Details

Maven plugin

Steps to reproduce

Run KotlinSpringServerCodegenTest.doNotGenerateRequestParamForObjectQueryParam with either of the definitions listed above.

The test will fail.

Related issues/PRs

Issue #8080 was supposed to fix it but it only works when the model definition is fixed.

We target a dynamic Map<String, String> (hence the additionalProperties) to implement a dynamic search: we can't possibly list all possible criteria.

Suggest a fix

Looks like the mustache template is src/main/resources/kotlin-spring/queryParams.mustache but my knowledge ends there. I don't know how to add additional condition to mustache.

A condition which would involve something along the lines:

• query parameter
• schema is an object no matter how it's defined

Start with src/main/resources/kotlin-spring/queryParams.mustache and run KotlinSpringServerCodegenTest.doNotGenerateRequestParamForObjectQueryParam using either OpenAPI definition from the issue. Trace how object query parameters with additionalProperties are rendered. Done means the test passes and the generated parameter no longer has an unnecessary @RequestParam annotation.