[BUG][R] Generating R enums results in empty class with no values

Created by: Leo-Rutschmann

Description

I have noticed that R enums are not generated properly, that is, instead of a proper enum structure, an empty class is generated. In it, there is nothing but the to-/fromJSON-methods; the values of the enum - that are specified in the schema - are not present.

openapi-generator version

openapi generator 4.0.1 (gradle plugin)

OpenAPI declaration file content or url

generated with json Schema:

{
  "openapi": "3.0.0",
  "info": {
    "title": "JSON test",
    "version": "1.0.0-SNAPSHOT"
  },
  "paths": {
  },
  "components": {
    "schemas": {
      "EnumTest": {
        "enum": [
          "One",
          "Two",
          "Three"
        ],
        "type": "string"
      }
    }
  }
}

Command line used for generation

task generate_R_test(type: org.openapitools.generator.gradle.plugin.tasks.GenerateTask) { inputSpec = "$rootDir/src/schema/new/test.schema.json".toString() outputDir = "$rootDir/src/data/r_model/test".toString() generatorName = 'r'

systemProperties = [
    models: "", // generate only models, but all of them
]

}

Steps to reproduce

1. use the gradle plugin with the above command to generate the enum
2. open the enum file (enum_test.R)
3. see that it generates an empty class without any of the enum values

Related issues/PRs

I have seearched for this issue but not found a similar case for R (only for Javascript, see https://github.com/swagger-api/swagger-codegen/issues/4819, but I do not know how helpful that will be)

Suggest a fix

I am not really familiar with the whole code, but upon looking at the code, I think the problem is that model.moustache is also used to generate enums. Because the values are described differently in the Schema, they might not be recognised properly