[BUG] [R] Initialize validation/check of an enum parameter

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

Summary: Initialize validation/check of an enum parameter in the outer R6 class against an empty vector.

In the example below:

• The outer component contains a kind property of type my_enum
• The my_enum component has two enum cases x and y
• The initialize function of outer checks kind with respect to the empty vector c(), hence this condition is always false:

  initialize = function(`kind`, ...) {
      if (!missing(`kind`)) {
        if (!(`kind` %in% c())) {
          stop(paste("Error! \"", `kind`, "\" cannot be assigned to `kind`. Must be .", sep = ""))
        }
        stopifnot(R6::is.R6(`kind`))
        self$`kind` <- `kind`
      }
    },

openapi-generator version

7.4.0-SNAPSHOT (via docker openapitools/openapi-generator-cli:latest)

OpenAPI declaration file content or url

{
  "openapi": "3.0.3",
  "info": {
    "title": "test",
    "version": "1.0.0"
  },
  "paths":{
  },
  "components": {
    "schemas": {
      "outer": {
        "type": "object",
        "additionalProperties": false,
        "required": [
          "kind"
        ],
        "properties": {
          "kind": {
            "$ref": "#/components/schemas/my_enum"
          }
        }
      },
      "my_enum": {
        "type": "string",
        "enum": [
          "x",
          "y"
        ]
      }
    }
  }
}

Generation Details

Steps to reproduce

docker run --user 1000:1000 --rm -v /tmp/test:/test openapitools/openapi-generator-cli:latest generate --global-property models -i /test/test.json -g r -o /test

Related issues/PRs

Possibly related to (but not sure):

• https://github.com/OpenAPITools/openapi-generator/issues/13469

Suggest a fix

Reproduce the generated R models with the provided OpenAPI declaration and Docker command, focusing on the outer R6 class's initialize function. Compare its enum validation for the referenced my_enum property with the declared x and y cases; done means the generated validation no longer checks against an empty vector and accepts valid enum values while rejecting invalid ones.